Individual P. Speelmans, Ed. Internet-Draft THEO Technologies Intended status: Informational 12 April 2023 Expires: 14 October 2023 HESP - High Efficiency Streaming Protocol draft-theo-hesp-04 Abstract This document describes a protocol for delivering multimedia data, enabling ultra-low latency and fast channel change over HTTP networks. It specifies the data format of the files and the actions to be taken by the server (sender) and the clients (receivers) of the streams. It describes version 2 of this protocol. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 14 October 2023. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. This document may not be modified, and derivative works of it may not be created, except to format it for publication as an RFC or to translate it into languages other than English. Speelmans Expires 14 October 2023 [Page 1] Internet-Draft HESP April 2023 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. HESP components . . . . . . . . . . . . . . . . . . . . . 4 2.2. Two complementary streams . . . . . . . . . . . . . . . . 5 2.3. HESP object model . . . . . . . . . . . . . . . . . . . . 6 2.4. Reference flow . . . . . . . . . . . . . . . . . . . . . 7 3. HESP Manifest . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1. Timestamps . . . . . . . . . . . . . . . . . . . . . . . 8 3.1.1. Manifest Timestamp and Media Timestamp . . . . . . . 9 3.1.2. Sequence Numbers . . . . . . . . . . . . . . . . . . 9 3.1.3. Calculating the Sequence Number of an Initialization Packet . . . . . . . . . . . . . . . . . . . . . . . 9 3.2. Manifest data types . . . . . . . . . . . . . . . . . . . 10 3.2.1. Additional JSON data types . . . . . . . . . . . . . 10 3.2.2. ManifestType . . . . . . . . . . . . . . . . . . . . 11 3.2.3. TimeSource . . . . . . . . . . . . . . . . . . . . . 14 3.2.4. ScaledValue . . . . . . . . . . . . . . . . . . . . . 14 3.2.5. PresentationType . . . . . . . . . . . . . . . . . . 14 3.2.6. TimeBounds . . . . . . . . . . . . . . . . . . . . . 16 3.2.7. AudioSwitchingSetType . . . . . . . . . . . . . . . . 17 3.2.8. SwitchingSetProtection . . . . . . . . . . . . . . . 22 3.2.9. SwitchingSetProtectionSystem . . . . . . . . . . . . 22 3.2.10. VideoSwitchingSetType . . . . . . . . . . . . . . . . 24 3.2.11. MetadataSwitchingSetType . . . . . . . . . . . . . . 28 3.2.12. AudioTrackType . . . . . . . . . . . . . . . . . . . 31 3.2.13. VideoTrackType . . . . . . . . . . . . . . . . . . . 36 3.2.14. Resolution . . . . . . . . . . . . . . . . . . . . . 41 3.2.15. MetadataTrackType . . . . . . . . . . . . . . . . . . 41 3.2.16. SegmentType . . . . . . . . . . . . . . . . . . . . . 45 3.2.17. PresentationEventType . . . . . . . . . . . . . . . . 45 3.2.18. PresentationEventTimeBounds . . . . . . . . . . . . . 46 3.3. Manifest requests . . . . . . . . . . . . . . . . . . . . 47 3.3.1. Manifest responses . . . . . . . . . . . . . . . . . 48 3.4. Addressing of content requests . . . . . . . . . . . . . 48 3.4.1. Content request URL resolution . . . . . . . . . . . 48 3.4.2. Requesting using an identifier and the content request URL . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.5. Manifest example . . . . . . . . . . . . . . . . . . . . 50 4. Initialization Stream . . . . . . . . . . . . . . . . . . . . 50 4.1. Initialization Stream purpose . . . . . . . . . . . . . . 50 4.2. Initialization Packet format . . . . . . . . . . . . . . 50 4.2.1. Video Initialization Packet . . . . . . . . . . . . . 50 4.2.2. Audio Initialization Packet . . . . . . . . . . . . . 51 4.2.3. Constraint on media information . . . . . . . . . . . 51 4.2.4. CMAF header . . . . . . . . . . . . . . . . . . . . . 51 4.2.5. Event message information . . . . . . . . . . . . . . 52 Speelmans Expires 14 October 2023 [Page 2] Internet-Draft HESP April 2023 4.3. Initialization Stream addressing . . . . . . . . . . . . 52 4.3.1. Initialization Stream requests . . . . . . . . . . . 52 4.3.2. Initialization Stream responses . . . . . . . . . . . 53 5. Continuation Stream . . . . . . . . . . . . . . . . . . . . . 54 5.1. Continuation Stream format . . . . . . . . . . . . . . . 54 5.1.1. Media content . . . . . . . . . . . . . . . . . . . . 54 5.2. Continuation Segment availability . . . . . . . . . . . . 54 5.3. Continuation Stream addressing . . . . . . . . . . . . . 55 5.3.1. Continuation Stream URLs . . . . . . . . . . . . . . 55 5.3.2. Continuation Stream requests . . . . . . . . . . . . 56 5.3.3. Continuation Stream responses . . . . . . . . . . . . 56 6. Timed metadata . . . . . . . . . . . . . . . . . . . . . . . 59 6.1. Metadata Tracks . . . . . . . . . . . . . . . . . . . . . 59 6.2. Metadata events . . . . . . . . . . . . . . . . . . . . . 59 6.2.1. In-band events . . . . . . . . . . . . . . . . . . . 59 6.2.2. Out-of-band events . . . . . . . . . . . . . . . . . 62 7. Content protection . . . . . . . . . . . . . . . . . . . . . 62 7.1. Common encryption support . . . . . . . . . . . . . . . . 62 7.2. HESP Manifest . . . . . . . . . . . . . . . . . . . . . . 62 7.3. CMAF box structure . . . . . . . . . . . . . . . . . . . 63 7.3.1. Initialization Stream . . . . . . . . . . . . . . . . 63 7.3.2. Continuation Stream . . . . . . . . . . . . . . . . . 64 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 64 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 64 10. Security Considerations . . . . . . . . . . . . . . . . . . . 65 11. Normative References . . . . . . . . . . . . . . . . . . . . 65 12. Informative References . . . . . . . . . . . . . . . . . . . 67 Appendix A. Example usage . . . . . . . . . . . . . . . . . . . 67 A.1. Manifest . . . . . . . . . . . . . . . . . . . . . . . . 67 A.1.1. Retrieving the Manifest . . . . . . . . . . . . . . . 67 A.1.2. Timing information . . . . . . . . . . . . . . . . . 72 A.1.3. Content addressing . . . . . . . . . . . . . . . . . 73 A.2. Initialization Stream . . . . . . . . . . . . . . . . . . 74 A.2.1. Retrieving Initialization Packets . . . . . . . . . . 74 A.2.2. Parsing offset information . . . . . . . . . . . . . 75 A.3. Continuation Stream . . . . . . . . . . . . . . . . . . . 75 A.3.1. Retrieving Continuation Segments . . . . . . . . . . 75 Appendix B. CDNs . . . . . . . . . . . . . . . . . . . . . . . . 76 Appendix C. HESP Profiles (using H.264 as video codec) . . . . . 76 C.1. Maximal Gain Profile . . . . . . . . . . . . . . . . . . 76 C.2. Compatibility Profile . . . . . . . . . . . . . . . . . . 77 C.2.1. Example . . . . . . . . . . . . . . . . . . . . . . . 78 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 79 Speelmans Expires 14 October 2023 [Page 3] Internet-Draft HESP April 2023 1. Introduction Viewers are more demanding than ever, calling for a streaming protocol that combines ultra-low latency, fast zapping and cost- effective scalability. HESP is an HTTP-based streaming approach that works with standard contribution feeds from (live) productions, standard encoders, albeit specifically configured, a HESP compliant packager, regular CDNs and an HESP compliant player. HESP offers sub-second latency, near real-time interactivity, fast startup and channel change times and cost-effective scalability up to millions of viewers. The purpose of this document is to facilitate interoperability between HESP implementations by describing the media transmission protocol. This document describes version 2 of the protocol. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2. Overview This section contains an overview of the HESP protocol and its building blocks. 2.1. HESP components HESP follows a regular approach to online video streaming. The content is ingested and transcoded in different qualities. Each quality requires two streams. The encoded streams are packaged by an HESP packager and made available via an origin server. An HESP player requests the stream using HTTP requests. A CDN can be used. _________ ________ __________ ________ _____ ________ | | | | | | | | | | | | | Input |\| xcoder |\| packager |\| origin |\| CDN |\| HESP | | Streams |/| |/| |/| |/| |/| player | |_________| |________| |__________| |________| |_____| |________| Figure 1: HESP chain from source to playback Speelmans Expires 14 October 2023 [Page 4] Internet-Draft HESP April 2023 2.2. Two complementary streams HESP is based on using two streams for each track, the Initialization Stream and the Continuation Stream. The encoder MUST ensure that the corresponding media data of both streams are issued with synchronized presentation timestamps. The packager MUST ensure this data remains in sync. The Initialization Stream consists of Initialization Packets. Initialization Packets MUST be individually addressable. An Initialization Packet MUST contain an independent media sample, the reference to the segment and the position in the segment where the Continuation Stream can start. Since the packet starts with an independent sample, playback can start with any Initialization Packet. The Continuation Stream can start playback immediately after an Initialization Packet, allowing for very fast channel start and switch times. This mechanism puts referencing limitations to the Continuation Stream. When a reference is made from the Initialization Stream to a Continuation Stream, all data needed to render the sample with the subsequent Presentation timestamp MUST be available at the reference offset. In addition, the samples in the Initialization Stream and the samples in the Continuation Stream MUST be aligned. That is, the corresponding media samples of both streams MUST have the same PTS and MUST be made available at the same time. The Continuation Stream is addressed using byte-range requests. The Continuation Stream SHOULD be published in chunks in order to reduce end-to-end latency. The player receives the Initialization Packet, initializes the decoder, puts the media data in the decoder buffer, and requests the subsequent media data from the Continuation Stream (using HTTP Range requests, starting by the range offset given by the Initialization Packet.) time sequence T1 T2 T3 T4 T5 T6 T7 T8 +----+----+----+----+----+----+----+----+ initialization stream | I1 | I2 | I3 | I4 | I5 | I6 | I7 | I8 | +----+----+----+----+----+----+----+----+ +----+----+----+----+----+----+----+----+ continuation stream | C1 | C2 | C3 | C4 | C5 | C6 | C7 | C8 | +----+----+----+----+----+----+----+----+ +----+----+----+----+----+----+ playback buffer | I3 | C4 | C5 | C6 | C7 | C8 | +----+----+----+----+----+----+ Figure 2: Start of an HESP stream Speelmans Expires 14 October 2023 [Page 5] Internet-Draft HESP April 2023 2.3. HESP object model The object model follows the CMAF media object model [CMAF]. A Track is used to contain media samples (audio or video) or metadata. It consists of a Continuation Stream and (except for metadata Tracks) an Initialization Stream. The Initialization Stream consists of Initialization Packets, where each such packet MUST contain a CMAF Header and possibly a CMAF Fragment. Each Initialization Packet MUST be individually addressable through Sequence Numbers. It is further explained in Section 4. The Continuation Stream consists of Continuation Segments. These Segments MUST consist of CMAF Chunks that can be sent individually to clients. It is further explained in Section 5. A Switching Set groups together Tracks that contain the same content but with different encoding parameters (e.g., different resolution or different bitrate). A client is able to seamlessly switch between Tracks of a Switching Set as a result. If multiple Switching Sets contain differing content but are aligned in their timings (e.g., multiple view perspectives on the same performance or different languages of the same audio), we can consider them Aligned Switching Sets. A Selection Set groups together multiple Switching Sets of the same media type. HESP currently allows 3 Selection Sets: audio, video and metadata Selection Sets. A Presentation contains the Selection Sets for a given period of time. Multiple Presentations together form a continuous timeline of media content, even though each Presentation might have different content, encodings or timestamps. It can be an advertisement, or a part of a show, or the first half of a game,... The Presentation is the lowest granularity inside a Manifest. All Tracks of a Presentation MUST have media data for the full duration of the Presentation. The Manifest informs clients of the aforementioned data structure and must be retrieved before any media data. The format of the Manifest is detailed in Section 3. Speelmans Expires 14 October 2023 [Page 6] Internet-Draft HESP April 2023 A new Manifest is not needed to request a new Segment. Segment addressing can happen automatically within a Presentation for an efficient and continuous delivery of the Continuation Stream. A Manifest is only obligated to be updated before the start of a new Presentation. This gives the opportunity for low frequency Manifest updates, though this update rate can be freely configured. Since Presentations can be of unknown duration, a different mechanism is used to signal a new Presentation to a client. To that extent, in-band metadata events are introduced in the Continuation Stream. Such an event can signal the client to retrieve a new Manifest, when information about an upcoming Presentation becomes available. 2.4. Reference flow +---------+ +---------+ | Player | | Origin | +---------+ +---------+ | | _____________|_____________________________________________|_____ ! LOOP / all presentations | ! !_______/ | | ! ! | | ! ! | request Manifest file | ! ! |-------------------------------------------->| ! ! | | ! ! | Return Manifest | ! ! |<--------------------------------------------| ! ! | | ! ! | parse Manifest | ! ! |--------------- | ! ! | | | ! ! |<-------------- | ! ! | | ! ! | | ! ! | Request Initialization Packet | ! ! |-------------------------------------------->| ! ! | | ! ! | Return Initialization Packet | ! ! |<--------------------------------------------| ! ! | | ! ! | Initialize decode pipeline | ! ! |--------------------------- | ! ! | | | ! ! |<-------------------------- | ! ! | | ! ! | Parse position information | ! ! | of the corresponding data | ! Speelmans Expires 14 October 2023 [Page 7] Internet-Draft HESP April 2023 ! | in the Continuation Stream | ! ! |-------------------------- | ! ! | | | ! ! |<------------------------- | ! ! | | ! ! | | ! ! | Request Continuation Stream: | ! ! | (Segment n) byte-range [now, -) | ! ! |-------------------------------------------->| ! ! | | ! ! | Return CMAF Fragments until the | ! ! | end of the Segment | ! ! |<--------------------------------------------| ! ! __________|_____________________________________________|__ ! ! ! LOOP / all Segments of the Presentation | ! ! ! !_______/ | | ! ! ! ! | | ! ! ! ! | Request Continuation Stream: | ! ! ! ! | (Segment n+i) without byte-range | ! ! ! ! |-------------------------------------------->| ! ! ! ! | | ! ! ! ! | Return CMAF Fragments until the | ! ! ! ! | end of the Segment | ! ! ! ! |<--------------------------------------------| ! ! ! ! | | ! ! ! !__________|_____________________________________________|__! ! ! | | ! !_____________|_____________________________________________|_____! | ! | ! Figure 3: HESP reference flow Though the manifest file is shared, video, audio and metadata (subtitles) media data MUST be distributed separately. They each require separate requests from the client. 3. HESP Manifest The first step for playback of an HESP stream is to fetch a Manifest. It contains information on the available Tracks and how to request content from every Track's Initialization and Continuation Streams. 3.1. Timestamps Speelmans Expires 14 October 2023 [Page 8] Internet-Draft HESP April 2023 3.1.1. Manifest Timestamp and Media Timestamp A distinction is made between Manifest Timestamps and Media Timestamps in the definitions below. Media Timestamps MUST represent Presentation timestamps as they are given by the media data itself. Manifest Timestamps MUST define those same Media Timestamps, but with an additional offset such that the timestamps of all Tracks of a Presentation are aligned. This offset MUST be given by the Manifest for each Track or Switching Set. For example, consider the first Segment of a Track with Media Timestamps starting at 0 seconds. This Track is part of the second Presentation of an HESP stream. The first Presentation has run for a significant amount of time and the second Presentation follows immediately after the first Presentation ends. In this case, the Manifest Timestamps of the second Presentation must succeed the Manifest Timestamps of the first Presentation. As a result, the Media Timestamps and Manifest Timestamps of the second Presentation now differ. An offset must be given by the Manifest in order to inform clients about this difference between timestamp types for each Track of the second Presentation. An example of this distinction is given in Appendix A.1.2. 3.1.2. Sequence Numbers Each Initialization Packet belonging to a Track is given a Sequence Number. This is a simple identifier used to retrieve specific Initialization Packets by the client. The Sequence Number is a positive integer that MUST be increased by 1 for each subsequent Initialization Packet of the same Track. The first Initialization Packet of all Tracks in all Switching Sets inside of a Presentation MUST contain the Manifest Timestamp for the start of that Presentation within the interval of the first presentation time of that Initialization Packet and the sum of the presentation time and all durations of the frames in that Initialization Packet. 3.1.3. Calculating the Sequence Number of an Initialization Packet To calculate the Sequence Number of a chosen Initialization Packet, the Manifest provides the client multiple values. Each active Presentation MUST contain both its current Manifest Timestamp and, for each Track, the Sequence Number of the first Initialization Packet and the (constant) frame rate. It is given that: * the frame rate MUST be constant for each Track. Speelmans Expires 14 October 2023 [Page 9] Internet-Draft HESP April 2023 * Initialization Packets MUST become available in real-time. * Sequence Numbers MUST be increased by 1 per Initialization Packet. * the Sequence Number and Manifest Timestamp of the first Initialization Packet for a Track are given by the Manifest. As a result, it is possible to derive Sequence Numbers for arbitrary Initialization Packets. By taking the initial Sequence Number of a Track, its associated Manifest Timestamp and the frame rate, it is possible to calculate the number of frames between the initial Sequence Number and any later Sequence Number of an Initialization Packet. For example, for a Video Track the full calculation can be performed as follows: calculateSequenceNumber(timestamp) = floor((timestamp - presentation.timeBounds.startTime / presentation.timeBounds.scale) * videoTrack.frameRate) + videoTrack.startSequenceNumber For example, suppose the start Sequence Number would be 34 at Manifest Timestamp 00:00:01.360 for a Track with a frame rate of 25 fps. To find the Sequence Number at Manifest Timestamp 00:00:04.120, the difference between both frames should be calculated. This means that the Sequence Number for the provided Manifest Timestamp is (4.120s - 1.360s) * 25fps + 34 = 103. In case the encoder suffers from drift and is not synchronized with a wall clock, a packager SHOULD compensate for this drift by creating a new Presentation. 3.2. Manifest data types The Manifest MUST be formatted as a JSON file. All data types used in the information below MUST satisfy the JavaScript Object Notation specification [RFC8259]. In regard to the definition of numbers within the JSON specification, their range and precision are implementation-dependent. It should be noted that for interoperability, numbers SHOULD be representable using IEEE 754 double-precision numbers. Some additional data types are introduced on top of the JSON specification to narrow the allowed values of some fields further. 3.2.1. Additional JSON data types Speelmans Expires 14 October 2023 [Page 10] Internet-Draft HESP April 2023 3.2.1.1. Integer An integer (or int) is a subset of the number type defined in the JSON specification, limited to integer numbers. Concretely, following Section 6 of the JSON specification, a number MUST NOT have a fraction part to be considered an integer. Note that as mentioned above, integers SHOULD be representable using IEEE 754 double- precision numbers. As a result, integers SHOULD be within the [(-2**53)+1, (2**53)-1] range to make sure implementations agree on the exact numeric value. 3.2.1.2. Unsigned integer An unsigned integer (or uint) is a subset of the integer type, only allowing for positive integer numbers. Concretely, following Section 6 of the JSON specification, an integer MUST NOT contain a minus to be considered an unsigned integer. 3.2.1.3. Enumeration An enumeration defines a list of constant strings, where a valid value of this type MUST equal one of these strings. The type is written as Enum(x, y, z), where x, y and z are the constant strings allowed to be used. 3.2.1.4. DateTime A DateTime MUST be formatted as a string in the format defined by ISO 8601 [ISO8601]: YYYY-MM-DDThh:mm:ss.mmmTZD where YYYY = four-digit year MM = two-digit month DD = two-digit day of the month hh = two digits of the hour (00 through 23) mm = two digits of a minute (00 through 59) ss = two digits of a second (00 through 59) mmm = three digits of a millisecond (000 through 999) TZD = time zone designator (Z or +hh:mm or -hh:mm) 3.2.2. ManifestType This data type represents the root of the Manifest. The structure consists of general playback information and a collection of Presentations. Speelmans Expires 14 October 2023 [Page 11] Internet-Draft HESP April 2023 The table below gives the possible fields. The "Required?" column indicates if a field is REQUIRED (Y) or OPTIONAL (N). +======================+=============+====+=========================+ | Attribute |Type |Req?| Description | +======================+=============+====+=========================+ | availabilityDuration |ScaledValue |Y | The amount of time (in | | | | | seconds) that live | | | | | content MUST be kept | | | | | available to be | | | | | retrieved by a client. | | | | | It is used to define | | | | | an interval [live - n, | | | | | live], where live is | | | | | the current live point | | | | | and n is | | | | | availabilityDuration, | | | | | where content MUST be | | | | | available for clients | | | | | of a live stream. For | | | | | VOD streams, this | | | | | value MUST be ignored. | +----------------------+-------------+----+-------------------------+ | creationDate |DateTime |Y | The timestamp of the | | | | | moment that this | | | | | specific Manifest was | | | | | created by the | | | | | packager (in local | | | | | packager time.) | +----------------------+-------------+----+-------------------------+ | fallbackPollRate |uint |Y | The number of seconds | | | | | a player SHOULD wait | | | | | to poll a new | | | | | Manifest, if it hasn't | | | | | requested any since | | | | | retrieving the current | | | | | Manifest. | +----------------------+-------------+----+-------------------------+ | manifestVersion |Enum("2.0.0")|Y | The version number of | | | | | the Manifest. | +----------------------+-------------+----+-------------------------+ | presentations |Presentation |Y | A list of all | | |Type[] | | Presentations that are | | | | | currently known. | +----------------------+-------------+----+-------------------------+ | streamType |Enum("live", |Y | Indicates whether the | | |"vod") | | stream is a live | | | | | stream (live) which | Speelmans Expires 14 October 2023 [Page 12] Internet-Draft HESP April 2023 | | | | does not have a known | | | | | ending, or a video on | | | | | demand stream (vod) | | | | | with a known ending | | | | | and duration. | +----------------------+-------------+----+-------------------------+ | activePresentation |string |N | The identifier of the | | | | | currently active | | | | | Presentation. This | | | | | value MUST be | | | | | available if | | | | | streamType equals | | | | | live, but MUST be | | | | | ignored if streamType | | | | | equals vod. | +----------------------+-------------+----+-------------------------+ | currentTime |ScaledValue |N | The most recent | | | | | composition timestamp | | | | | of any Track contained | | | | | by this Manifest when | | | | | this Manifest is | | | | | generated. It SHOULD | | | | | be specified in | | | | | Manifest Time, not in | | | | | Media Time (as that | | | | | could have different | | | | | offsets from Track to | | | | | Track.) This value | | | | | MUST be available if | | | | | streamType equals | | | | | live, but MUST be | | | | | ignored if streamType | | | | | equals vod. | +----------------------+-------------+----+-------------------------+ | contentBaseUrl |string |N | The base URL for all | | | | | content requests | | | | | relating to this | | | | | Manifest. See | | | | | Section 3.4 for more | | | | | information. | +----------------------+-------------+----+-------------------------+ | timeSource |TimeSource |N | A reference to a time | | | | | server with which the | | | | | packager is synced. | | | | | This value MUST be | | | | | ignored if streamType | | | | | equals vod. | +----------------------+-------------+----+-------------------------+ Speelmans Expires 14 October 2023 [Page 13] Internet-Draft HESP April 2023 Table 1 3.2.3. TimeSource A TimeSource is used to sync the packager and player internal clocks to make requests for data only once it is available. +===========+========+==========+==============================+ | Attribute | Type | Required | Description | +===========+========+==========+==============================+ | scheme | string | Y | A scheme id for the time | | | | | source as defined as a valid | | | | | @schemeIdURI in [DASH] | | | | | section 5.8.4.11 Table 32. | +-----------+--------+----------+------------------------------+ | value | string | Y | The information indicating | | | | | where the time source can be | | | | | found as indicated in [DASH] | | | | | section 5.8.5.7. | +-----------+--------+----------+------------------------------+ Table 2 3.2.4. ScaledValue In order to avoid rounding issues introduced through floating-point numbers, this structure defines two integers. The total value is calculated by dividing value over scale. +===========+======+==========+============================+ | Attribute | Type | Required | Description | +===========+======+==========+============================+ | value | int | Y | The defined integer value. | +-----------+------+----------+----------------------------+ | scale | uint | N | If not defined, the scale | | | | | SHALL equal 1. | +-----------+------+----------+----------------------------+ Table 3 3.2.5. PresentationType This is the type definition of a Presentation. Speelmans Expires 14 October 2023 [Page 14] Internet-Draft HESP April 2023 +==========+============================+====+======================+ |Attribute | Type |Req?| Description | +==========+============================+====+======================+ |id | string |Y | The unique | | | | | identifier for this | | | | | Presentation. It | | | | | MUST be unique over | | | | | all Presentations | | | | | of this Manifest. | | | | | It MUST NOT change | | | | | over Manifest | | | | | updates. | +----------+----------------------------+----+----------------------+ |timeBounds| TimeBounds |Y | The time boundaries | | | | | of this | | | | | Presentation, in | | | | | Manifest Time. The | | | | | start time MUST be | | | | | announced at least | | | | | 2 seconds before | | | | | the Presentation is | | | | | active. The end | | | | | time of an active | | | | | Presentation MUST | | | | | be available at | | | | | least 2 seconds | | | | | before the actual | | | | | end of that | | | | | Presentation. The | | | | | startTime of the | | | | | TimeBounds MUST be | | | | | equal to the time | | | | | corresponding to | | | | | the | | | | | startSequenceNumber | | | | | of each Track. | +----------+----------------------------+----+----------------------+ |audio | AudioSwitchingSetType[] |N | The audio Selection | | | | | Set. It contains | | | | | all audio Switching | | | | | Sets of this | | | | | Presentation. If | | | | | not defined, this | | | | | value SHALL equal | | | | | an empty list. | +----------+----------------------------+----+----------------------+ |baseUrl | string |N | The base URL of | | | | | this Presentation. | Speelmans Expires 14 October 2023 [Page 15] Internet-Draft HESP April 2023 | | | | It is part of the | | | | | content base URLs | | | | | for all Switching | | | | | Sets belonging to | | | | | this Presentation. | | | | | See Section 3.4 for | | | | | more information. | +----------+----------------------------+----+----------------------+ |events | PresentationEventType[] |N | List of all | | | | | currently available | | | | | Presentation Events | | | | | related to this | | | | | Presentation. If | | | | | not defined, this | | | | | value SHALL equal | | | | | an empty list. | +----------+----------------------------+----+----------------------+ |metadata | MetadataSwitchingSetType[] |N | The metadata | | | | | Selection Set. It | | | | | contains all | | | | | metadata Switching | | | | | Sets of this | | | | | Presentation. If | | | | | not defined, this | | | | | value SHALL equal | | | | | an empty list. | +----------+----------------------------+----+----------------------+ |video | VideoSwitchingSetType[] |N | The video Selection | | | | | Set. It contains | | | | | all video Switching | | | | | Sets of this | | | | | Presentation. If | | | | | not defined, this | | | | | value SHALL equal | | | | | an empty list. | +----------+----------------------------+----+----------------------+ Table 4 3.2.6. TimeBounds A TimeBounds structure denotes a time interval with a start and end time. A start or end time may be undefined. The desired behavior in such a situation depends on the specific usage of the structure. These boundaries are inclusive at the start time and exclusive at the end time. I.e., if two TimeBounds need to be continuous, then the end time of the first one must equal the start time of the second. Speelmans Expires 14 October 2023 [Page 16] Internet-Draft HESP April 2023 +===========+======+==========+============================+ | Attribute | Type | Required | Description | +===========+======+==========+============================+ | startTime | uint | N | This value denotes the | | | | | start time in seconds when | | | | | divided by the timescale. | +-----------+------+----------+----------------------------+ | endTime | uint | N | This value denotes the end | | | | | time in seconds when | | | | | divided by the timescale. | +-----------+------+----------+----------------------------+ | scale | uint | N | If the timescale is not | | | | | defined, it SHALL equal 1. | +-----------+------+----------+----------------------------+ Table 5 3.2.7. AudioSwitchingSetType This is the type definition of an audio Switching Set. +=======================+==================+======+=================+ | Attribute | Type | Req? | Description | +=======================+==================+======+=================+ | id | string | Y | The unique | | | | | identifier for | | | | | this Switching | | | | | Set. It MUST | | | | | be unique | | | | | within its | | | | | Presentation. | +-----------------------+------------------+------+-----------------+ | language | string | Y | The language | | | | | of all audio | | | | | Tracks of this | | | | | Switching Set. | | | | | It MUST be | | | | | specified here | | | | | by its ISO | | | | | 639-2 | | | | | [ISO6392] | | | | | code. | +-----------------------+------------------+------+-----------------+ | tracks | AudioTrackType[] | Y | The collection | | | | | of all Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. | Speelmans Expires 14 October 2023 [Page 17] Internet-Draft HESP April 2023 +-----------------------+------------------+------+-----------------+ | alignId | string | N | A unique | | | | | identifier | | | | | that SHOULD be | | | | | set by all | | | | | Switching Sets | | | | | that are | | | | | Aligned | | | | | Switching Sets | | | | | with each | | | | | other. | +-----------------------+------------------+------+-----------------+ | baseUrl | string | N | The base URL | | | | | of this | | | | | Switching Set. | | | | | It is part of | | | | | the content | | | | | base URLs for | | | | | all Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. See | | | | | Section 3.4 | | | | | for more | | | | | information. | +-----------------------+------------------+------+-----------------+ | channels | uint | N | The audio | | | | | channel | | | | | configuration | | | | | of all audio | | | | | Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. It is | | | | | defined as the | | | | | total number | | | | | of audio | | | | | channels. | | | | | This value is | | | | | used for ABR | | | | | selection by | | | | | the player. | +-----------------------+------------------+------+-----------------+ | codecs | string | N | The definition | | | | | of the | | | | | codec(s) | | | | | necessary to | | | | | render the | Speelmans Expires 14 October 2023 [Page 18] Internet-Draft HESP April 2023 | | | | content of all | | | | | Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. It MUST | | | | | follow the ISO | | | | | File Format | | | | | Name Space as | | | | | defined by | | | | | [RFC6381]. If | | | | | this is not | | | | | defined, it | | | | | MUST be | | | | | defined on all | | | | | Tracks of this | | | | | Switching Set | | | | | separately. | +-----------------------+------------------+------+-----------------+ | continuationPattern | string | N | The URL | | | | | pattern used | | | | | to request | | | | | Continuation | | | | | Segments | | | | | belonging to | | | | | this Switching | | | | | Set. The | | | | | pattern MUST | | | | | include the | | | | | {segmentId} | | | | | string; see | | | | | Section 3.4 | | | | | for more | | | | | information. | | | | | If this is not | | | | | defined, it | | | | | MUST be | | | | | defined on all | | | | | Tracks of this | | | | | Switching Set | | | | | separately. | +-----------------------+------------------+------+-----------------+ | initializationPattern | string | N | The URL | | | | | pattern used | | | | | to request | | | | | Initialization | | | | | Packets | | | | | belonging to | | | | | this Switching | Speelmans Expires 14 October 2023 [Page 19] Internet-Draft HESP April 2023 | | | | Set. The | | | | | pattern MUST | | | | | include the | | | | | {initId} | | | | | string; see | | | | | Section 3.4 | | | | | for more | | | | | information. | | | | | If this is not | | | | | defined, it | | | | | MUST be | | | | | defined on all | | | | | Tracks of this | | | | | Switching Set | | | | | separately. | +-----------------------+------------------+------+-----------------+ | label | string | N | A human- | | | | | readable name | | | | | for this | | | | | Switching Set. | +-----------------------+------------------+------+-----------------+ | mediaTimeOffset | ScaledValue | N | The offset to | | | | | be added to | | | | | Manifest | | | | | Timestamps to | | | | | calculate | | | | | Media | | | | | Timestamps | | | | | contained by | | | | | Segments of | | | | | this Switching | | | | | Set. If | | | | | neither the | | | | | Track nor the | | | | | Switching Set | | | | | has this value | | | | | set, it SHALL | | | | | equal 0. | +-----------------------+------------------+------+-----------------+ | mimeType | string | N | The MIME type | | | | | of all content | | | | | belonging to | | | | | this Switching | | | | | Set. It MUST | | | | | be a valid | | | | | audio MIME | | | | | type. If not | | | | | set, the MIME | Speelmans Expires 14 October 2023 [Page 20] Internet-Draft HESP April 2023 | | | | type of all | | | | | content of | | | | | this Switching | | | | | Set SHALL | | | | | equal audio/ | | | | | mp4. | +-----------------------+------------------+------+-----------------+ | protection | SwitchingSet | N | The | | | Protection | | information | | | | | related to | | | | | content | | | | | protection for | | | | | all Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. | +-----------------------+------------------+------+-----------------+ | sampleRate | uint | N | The sample | | | | | rate (in Hz) | | | | | of all audio | | | | | Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. If this | | | | | is not | | | | | defined, it | | | | | MUST be | | | | | defined on all | | | | | Tracks of this | | | | | Switching Set | | | | | separately. | +-----------------------+------------------+------+-----------------+ | samplesPerFrame | uint | N | The number of | | | | | audio samples | | | | | in one frame. | | | | | If set, this | | | | | MUST apply to | | | | | each Track | | | | | belonging to | | | | | this Switching | | | | | Set that does | | | | | not define | | | | | this value | | | | | itself. If | | | | | neither the | | | | | Track nor the | | | | | Switching Set | | | | | has this value | Speelmans Expires 14 October 2023 [Page 21] Internet-Draft HESP April 2023 | | | | set, it SHALL | | | | | equal 1024. | +-----------------------+------------------+------+-----------------+ Table 6 3.2.8. SwitchingSetProtection The following fields are defined on the SwitchingSetProtection structure: +===========+================================+======+===============+ | Attribute | Type | Req? | Description | +===========+================================+======+===============+ | type | Enum("cenc", "cbcs") | Y | The | | | | | protection | | | | | scheme used | | | | | to encrypt | | | | | this | | | | | Switching | | | | | Set. | +-----------+--------------------------------+------+---------------+ | systems | SwitchingSetProtectionSystem[] | Y | Metadata | | | | | about the | | | | | DRM systems | | | | | that can be | | | | | used to | | | | | playback | | | | | this | | | | | Switching | | | | | Set. This | | | | | list MUST | | | | | contain at | | | | | least one | | | | | entry. | +-----------+--------------------------------+------+---------------+ Table 7 More information on content protection can be found in Section 7. 3.2.9. SwitchingSetProtectionSystem The following fields are defined on the SwitchingSetProtectionSystem structure: Speelmans Expires 14 October 2023 [Page 22] Internet-Draft HESP April 2023 +===========+======+==========+====================================+ | Attribute |Type | Required | Description | +===========+======+==========+====================================+ | pssh |string| N | A Base 64 encoded | | | | | ProtectionSystemSpecificHeaderBox. | | | | | If it is not defined in the | | | | | Manifest, then such a box MUST be | | | | | available in the Initialization | | | | | Stream of each Track belonging to | | | | | this Switching Set. | +-----------+------+----------+------------------------------------+ | schemeId |string| Y | A UUID [UUID] that uniquely | | | | | identifies the content protection | | | | | system. It should match the | | | | | System ID included in the pssh box | | | | | of this protection system. | +-----------+------+----------+------------------------------------+ Table 8 Additional attributes, such as license acquisition URLs, authorization-related URLs, specific initialization data (a default key ID) or others, MAY be defined for this structure, depending on the scheme identifier. Below, additional attributes that MUST be included are given for a subset of System IDs. If a System ID is not included here, then additional attributes MAY still be defined by the author of the content protection system and is considered out of scope of this document. +====================================+==================+=========+ |System ID |Attributes |Reference| +====================================+==================+=========+ |94ce86fb-07ff-4f43-adb8-93d2fa968ca2|FairPlayAttributes|Apple | | | |FairPlay | | | |Streaming| +------------------------------------+------------------+---------+ Table 9 3.2.9.1. FairPlayAttributes The following fields MUST be parsed from the SwitchingSetProtectionSystem structure when schemeId equals 94ce86fb- 07ff-4f43-adb8-93d2fa968ca2. More details about the requirements of these fields can be found in RFC 8216bis [I-D.pantos-hls-rfc8216bis]. Speelmans Expires 14 October 2023 [Page 23] Internet-Draft HESP April 2023 +=================+======+========+=================================+ |Attribute |Type |Required|Description | +=================+======+========+=================================+ |uri |string|Y |A URI that specifies how to | | | | |obtain the key. | +-----------------+------+--------+---------------------------------+ |keyFormat |string|N |Specifies how the key is | | | | |represented in the resource | | | | |identified by the uri. If not | | | | |defined, this value SHALL equal | | | | |identity. | +-----------------+------+--------+---------------------------------+ |keyFormatVersions|string|N |Indicate which version(s) used in| | | | |the formatting of the key this | | | | |instance complies with. The | | | | |value is a quoted-string | | | | |containing one or more positive | | | | |integers separated by the / | | | | |character (for example, "1", | | | | |"1/2", or "1/2/5"). If not | | | | |defined, this value SHALL equal | | | | |"1". | +-----------------+------+--------+---------------------------------+ |iv |string|N |A hexadecimal-sequence that | | | | |specifies a 128-bit unsigned | | | | |integer Initialization Vector to | | | | |be used with the key. | +-----------------+------+--------+---------------------------------+ |pssh |string|N |The pssh field of a | | | | |SwitchingSetProtectionSystem MUST| | | | |be ignored in the case of | | | | |FairPlay content protection. | | | | |Additionally, a | | | | |ProtectionSystemSpecificHeaderBox| | | | |MUST NOT be available in the | | | | |Initialization Stream of any | | | | |Track belonging to this Switching| | | | |Set in this case. | +-----------------+------+--------+---------------------------------+ Table 10 3.2.10. VideoSwitchingSetType This is the type definition of a video Switching Set. Speelmans Expires 14 October 2023 [Page 24] Internet-Draft HESP April 2023 +=======================+==================+======+=================+ | Attribute | Type | Req? | Description | +=======================+==================+======+=================+ | id | string | Y | The unique | | | | | identifier for | | | | | this Switching | | | | | Set. It MUST | | | | | be unique | | | | | within its | | | | | Presentation. | +-----------------------+------------------+------+-----------------+ | tracks | VideoTrackType[] | Y | The collection | | | | | of all Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. | +-----------------------+------------------+------+-----------------+ | alignId | string | N | A unique | | | | | identifier | | | | | that SHOULD be | | | | | set by all | | | | | Switching Sets | | | | | that are | | | | | Aligned | | | | | Switching Sets | | | | | with each | | | | | other. | +-----------------------+------------------+------+-----------------+ | baseUrl | string | N | The base URL | | | | | of this | | | | | Switching Set. | | | | | It is part of | | | | | the content | | | | | base URLs for | | | | | all Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. See | | | | | Section 3.4 | | | | | for more | | | | | information. | +-----------------------+------------------+------+-----------------+ | codecs | string | N | The definition | | | | | of the | | | | | codec(s) | | | | | necessary to | | | | | render the | | | | | content of all | Speelmans Expires 14 October 2023 [Page 25] Internet-Draft HESP April 2023 | | | | Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. It MUST | | | | | follow the ISO | | | | | File Format | | | | | Name Space as | | | | | defined by | | | | | [RFC6381]. If | | | | | this is not | | | | | defined, it | | | | | MUST be | | | | | defined on all | | | | | Tracks of this | | | | | Switching Set | | | | | separately. | +-----------------------+------------------+------+-----------------+ | continuationPattern | string | N | The URL | | | | | pattern used | | | | | to request | | | | | Continuation | | | | | Segments | | | | | belonging to | | | | | this Switching | | | | | Set. The | | | | | pattern MUST | | | | | include the | | | | | {segmentId} | | | | | string; see | | | | | Section 3.4 | | | | | for more | | | | | information. | | | | | If this is not | | | | | defined, it | | | | | MUST be | | | | | defined on all | | | | | Tracks of this | | | | | Switching Set | | | | | separately. | +-----------------------+------------------+------+-----------------+ | frameRate | ScaledValue | N | The frame rate | | | | | of all video | | | | | Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. If this | | | | | is not | | | | | defined, then | Speelmans Expires 14 October 2023 [Page 26] Internet-Draft HESP April 2023 | | | | every Track | | | | | MUST set its | | | | | frame rate | | | | | separately. | +-----------------------+------------------+------+-----------------+ | initializationPattern | string | N | The URL | | | | | pattern used | | | | | to request | | | | | Initialization | | | | | Packets | | | | | belonging to | | | | | this Switching | | | | | Set. The | | | | | pattern MUST | | | | | include the | | | | | {initId} | | | | | string; see | | | | | Section 3.4 | | | | | for more | | | | | information. | | | | | If this is not | | | | | defined, it | | | | | MUST be | | | | | defined on all | | | | | Tracks of this | | | | | Switching Set | | | | | separately. | +-----------------------+------------------+------+-----------------+ | label | string | N | A human- | | | | | readable name | | | | | for this | | | | | Switching Set. | +-----------------------+------------------+------+-----------------+ | mediaTimeOffset | ScaledValue | N | The offset to | | | | | be added to | | | | | Manifest | | | | | Timestamps to | | | | | calculate | | | | | Media | | | | | Timestamps | | | | | contained by | | | | | Segments of | | | | | this Switching | | | | | Set. If | | | | | neither the | | | | | Track nor the | | | | | Switching Set | | | | | has this value | Speelmans Expires 14 October 2023 [Page 27] Internet-Draft HESP April 2023 | | | | set, it SHALL | | | | | equal 0. | +-----------------------+------------------+------+-----------------+ | mimeType | string | N | The MIME type | | | | | of all content | | | | | belonging to | | | | | this Switching | | | | | Set. It MUST | | | | | be a valid | | | | | video MIME | | | | | type. If not | | | | | set, the MIME | | | | | type of all | | | | | content of | | | | | this Switching | | | | | Set SHALL | | | | | equal video/ | | | | | mp4. | +-----------------------+------------------+------+-----------------+ | protection | SwitchingSet | N | The | | | Protection | | information | | | | | related to | | | | | content | | | | | protection for | | | | | all Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. | +-----------------------+------------------+------+-----------------+ Table 11 3.2.11. MetadataSwitchingSetType This is the type definition of a metadata Switching Set. +=====================+=====================+====+==================+ | Attribute | Type |Req?| Description | +=====================+=====================+====+==================+ | id | string |Y | The unique | | | | | identifier for | | | | | this Switching | | | | | Set. It MUST be | | | | | unique within | | | | | its | | | | | Presentation. | +---------------------+---------------------+----+------------------+ | mimeType | string |Y | The MIME type | Speelmans Expires 14 October 2023 [Page 28] Internet-Draft HESP April 2023 | | | | of all content | | | | | belonging to | | | | | this Switching | | | | | Set. | +---------------------+---------------------+----+------------------+ | tracks | MetadataTrackType[] |Y | The collection | | | | | of all Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. | +---------------------+---------------------+----+------------------+ | schemeId | string |Y | An identifier | | | | | that denotes | | | | | the type of | | | | | metadata | | | | | contained by | | | | | this metadata | | | | | Switching Set. | | | | | Client behavior | | | | | may differ | | | | | depending on | | | | | the vendor- | | | | | specific | | | | | identifier set | | | | | here. | +---------------------+---------------------+----+------------------+ | alignId | string |N | A unique | | | | | identifier that | | | | | SHOULD be set | | | | | by all | | | | | Switching Sets | | | | | that are | | | | | Aligned | | | | | Switching Sets | | | | | with each | | | | | other. | +---------------------+---------------------+----+------------------+ | baseUrl | string |N | The base URL of | | | | | this Switching | | | | | Set. It is part | | | | | of the content | | | | | base URLs for | | | | | all Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. See | | | | | Section 3.4 for | | | | | more | Speelmans Expires 14 October 2023 [Page 29] Internet-Draft HESP April 2023 | | | | information. | +---------------------+---------------------+----+------------------+ | codecs | string |N | The definition | | | | | of the codec(s) | | | | | necessary to | | | | | render the | | | | | content of all | | | | | Tracks | | | | | belonging to | | | | | this Switching | | | | | Set. It MUST | | | | | follow the ISO | | | | | File Format | | | | | Name Space as | | | | | defined by | | | | | [RFC6381]. If | | | | | this Switching | | | | | Set does not | | | | | define it, then | | | | | it must be | | | | | defined on all | | | | | its Tracks | | | | | separately. | +---------------------+---------------------+----+------------------+ | continuationPattern | string |N | The URL pattern | | | | | used to request | | | | | Continuation | | | | | Segments | | | | | belonging to | | | | | this Switching | | | | | Set. The | | | | | pattern MUST | | | | | include the | | | | | {segmentId} | | | | | string; see | | | | | Section 3.4 for | | | | | more | | | | | information. | | | | | If this is not | | | | | defined, it | | | | | MUST be defined | | | | | on all Tracks | | | | | of this | | | | | Switching Set | | | | | separately. | +---------------------+---------------------+----+------------------+ | label | string |N | A human- | | | | | readable name | Speelmans Expires 14 October 2023 [Page 30] Internet-Draft HESP April 2023 | | | | for this | | | | | Switching Set. | +---------------------+---------------------+----+------------------+ | language | string |N | The language of | | | | | all Tracks of | | | | | the metadata | | | | | Switching Set. | | | | | It MUST be | | | | | specified here | | | | | by its ISO | | | | | 639-2 [ISO6392] | | | | | code. | +---------------------+---------------------+----+------------------+ | mediaTimeOffset | ScaledValue |N | The offset to | | | | | be added to | | | | | Manifest | | | | | Timestamps to | | | | | calculate Media | | | | | Timestamps | | | | | contained by | | | | | Segments of | | | | | this Switching | | | | | Set. If neither | | | | | the Track nor | | | | | the Switching | | | | | Set has this | | | | | value set, it | | | | | SHALL equal 0. | +---------------------+---------------------+----+------------------+ Table 12 3.2.12. AudioTrackType This is the type definition of an audio Track. +=======================+===============+======+====================+ | Attribute | Type | Req? | Description | +=======================+===============+======+====================+ | bandwidth | uint | Y | The peak bitrate | | | | | of this Track. | | | | | It is denoted in | | | | | bits per second. | | | | | The measured | | | | | bitrates of all | | | | | Segments of the | | | | | Track MUST NOT | | | | | exceed this | Speelmans Expires 14 October 2023 [Page 31] Internet-Draft HESP April 2023 | | | | value. This | | | | | value is used to | | | | | aid in ABR | | | | | decisions by the | | | | | player. | +-----------------------+---------------+------+--------------------+ | id | string | Y | The unique | | | | | identifier for | | | | | this Track. It | | | | | MUST be unique | | | | | within its | | | | | Switching Set. | +-----------------------+---------------+------+--------------------+ | segments | SegmentType[] | Y | The metadata of | | | | | the Segments | | | | | contained by this | | | | | Track at the | | | | | moment of | | | | | Manifest | | | | | creation. If a | | | | | segment duration | | | | | is not set, then | | | | | each Segment MUST | | | | | be announced by | | | | | the Manifest | | | | | before it is | | | | | active. More | | | | | information about | | | | | Segment | | | | | availability is | | | | | given in | | | | | Section 5.2. | +-----------------------+---------------+------+--------------------+ | startSegmentId | uint | N | The identifier of | | | | | the first Segment | | | | | in the | | | | | Continuation | | | | | Stream of this | | | | | Track. If not | | | | | defined, this | | | | | value SHALL equal | | | | | 0. | +-----------------------+---------------+------+--------------------+ | startSequenceNumber | uint | N | The Sequence | | | | | Number of the | | | | | first | | | | | Initialization | | | | | Packet in this | Speelmans Expires 14 October 2023 [Page 32] Internet-Draft HESP April 2023 | | | | Track. It MUST | | | | | denote the | | | | | Sequence Number | | | | | of the first | | | | | Initialization | | | | | Packet of this | | | | | Track which was | | | | | published in this | | | | | Track. If not | | | | | defined, this | | | | | value SHALL equal | | | | | 0. | +-----------------------+---------------+------+--------------------+ | averageBandwidth | uint | N | The average | | | | | bitrate of this | | | | | Track, denoted in | | | | | bits per second. | | | | | It is expected | | | | | that over a | | | | | duration of 10 | | | | | minutes, the | | | | | average bitrate | | | | | of this Track | | | | | SHALL be within | | | | | 5% of the given | | | | | value. This | | | | | value is used to | | | | | aid in ABR | | | | | decisions by the | | | | | player. | +-----------------------+---------------+------+--------------------+ | baseUrl | string | N | The base URL of | | | | | this Track. It | | | | | is part of the | | | | | content base URLs | | | | | used to request | | | | | this Track's | | | | | Initialization | | | | | Packets and | | | | | Continuation | | | | | Segments. See | | | | | Section 3.4 for | | | | | more information. | +-----------------------+---------------+------+--------------------+ | channels | integer | N | The audio channel | | | | | configuration of | | | | | this audio Track, | | | | | defined as the | Speelmans Expires 14 October 2023 [Page 33] Internet-Draft HESP April 2023 | | | | total number of | | | | | audio channels in | | | | | the media data. | | | | | This is used for | | | | | ABR selection by | | | | | the player. | +-----------------------+---------------+------+--------------------+ | codecs | string | N | The definition of | | | | | the codec(s) | | | | | necessary to | | | | | render the | | | | | content of this | | | | | Track. It MUST | | | | | follow the ISO | | | | | File Format Name | | | | | Space as defined | | | | | by [RFC6381]. If | | | | | this is not | | | | | defined here, | | | | | then it MUST be | | | | | defined by the | | | | | Track's Switching | | | | | Set. | +-----------------------+---------------+------+--------------------+ | continuationPattern | string | N | The URL pattern | | | | | used to request | | | | | Continuation | | | | | Segments | | | | | belonging to this | | | | | Track. The | | | | | pattern needs to | | | | | include the | | | | | {segmentId} | | | | | string; see | | | | | Section 3.4 for | | | | | more information. | | | | | If this is not | | | | | defined here, | | | | | then it MUST be | | | | | defined by the | | | | | Track's Switching | | | | | Set. | +-----------------------+---------------+------+--------------------+ | label | string | N | A human-readable | | | | | name for this | | | | | Track. | +-----------------------+---------------+------+--------------------+ | initializationPattern | string | N | The URL pattern | Speelmans Expires 14 October 2023 [Page 34] Internet-Draft HESP April 2023 | | | | used to request | | | | | Initialization | | | | | Packets belonging | | | | | to this media | | | | | Track. The | | | | | pattern needs to | | | | | include the | | | | | {initId} string; | | | | | see Section 3.4 | | | | | for more | | | | | information. If | | | | | this is not | | | | | defined here, | | | | | then it MUST be | | | | | defined by the | | | | | Track's Switching | | | | | Set. | +-----------------------+---------------+------+--------------------+ | mediaTimeOffset | ScaledValue | N | The offset to be | | | | | added to Manifest | | | | | Timestamps to | | | | | calculate Media | | | | | Timestamps | | | | | contained by | | | | | segments of this | | | | | Track. If | | | | | neither the Track | | | | | nor the Switching | | | | | Set has this | | | | | value set, it | | | | | SHALL equal 0. | +-----------------------+---------------+------+--------------------+ | sampleRate | uint | N | The sample rate | | | | | (in Hz) of this | | | | | audio Track. If | | | | | this is not | | | | | defined here, | | | | | then it MUST be | | | | | defined by the | | | | | Track's Switching | | | | | Set. | +-----------------------+---------------+------+--------------------+ | samplesPerFrame | uint | N | The number of | | | | | audio samples in | | | | | one frame of this | | | | | audio Track. If | | | | | neither the Track | | | | | nor the Switching | Speelmans Expires 14 October 2023 [Page 35] Internet-Draft HESP April 2023 | | | | Set has this | | | | | value set, it | | | | | SHALL equal 1024. | +-----------------------+---------------+------+--------------------+ | segmentDuration | ScaledValue | N | The duration (in | | | | | seconds) of each | | | | | Segment contained | | | | | by this Track. | | | | | If this value is | | | | | set, then every | | | | | segmentDuration | | | | | seconds, a new | | | | | Segment SHOULD be | | | | | available. More | | | | | information about | | | | | the availability | | | | | is given in | | | | | Section 5.2. If | | | | | not set, then | | | | | each Segment MUST | | | | | be individually | | | | | defined by the | | | | | segments field. | +-----------------------+---------------+------+--------------------+ Table 13 For any attributes that also exist on AudioSwitchingSetType, if both AudioSwitchingSetType and AudioTrackType have a value for this attribute, then only the value set by AudioTrackType must be considered (except for the identifier and label.) 3.2.13. VideoTrackType This is the type definition of a video Track. +=======================+===============+======+====================+ | Attribute | Type | Req? | Description | +=======================+===============+======+====================+ | bandwidth | uint | Y | The peak bitrate | | | | | of this Track. | | | | | It is denoted in | | | | | bits per second. | | | | | The measured | | | | | bitrates of all | | | | | Segments of the | | | | | Track MUST NOT | | | | | exceed this | Speelmans Expires 14 October 2023 [Page 36] Internet-Draft HESP April 2023 | | | | value. This | | | | | value is used to | | | | | aid in ABR | | | | | decisions by the | | | | | player. | +-----------------------+---------------+------+--------------------+ | id | string | Y | The unique | | | | | identifier for | | | | | this Track. It | | | | | MUST be unique | | | | | within its | | | | | Switching Set. | +-----------------------+---------------+------+--------------------+ | resolution | Resolution | Y | The resolution of | | | | | this video Track. | +-----------------------+---------------+------+--------------------+ | segments | SegmentType[] | Y | The metadata of | | | | | the Segments | | | | | contained by this | | | | | Track at the | | | | | moment of | | | | | Manifest | | | | | creation. If a | | | | | segment duration | | | | | is not set, then | | | | | each Segment MUST | | | | | be announced by | | | | | the Manifest | | | | | before it is | | | | | active. More | | | | | information about | | | | | Segment | | | | | availability is | | | | | given in | | | | | Section 5.2. | +-----------------------+---------------+------+--------------------+ | startSegmentId | uint | N | The identifier of | | | | | the first Segment | | | | | in the | | | | | Continuation | | | | | Stream of this | | | | | Track. If not | | | | | defined, this | | | | | value SHALL equal | | | | | 0. | +-----------------------+---------------+------+--------------------+ | startSequenceNumber | uint | N | The Sequence | | | | | Number of the | Speelmans Expires 14 October 2023 [Page 37] Internet-Draft HESP April 2023 | | | | first | | | | | Initialization | | | | | Packet in this | | | | | Track. It MUST | | | | | denote the | | | | | Sequence Number | | | | | of the first | | | | | Initialization | | | | | Packet of this | | | | | Track which was | | | | | published in this | | | | | Track. If not | | | | | defined, this | | | | | value SHALL equal | | | | | 0. | +-----------------------+---------------+------+--------------------+ | averageBandwidth | uint | N | The average | | | | | bitrate of this | | | | | Track, denoted in | | | | | bits per second. | | | | | It is expected | | | | | that over a | | | | | duration of 10 | | | | | minutes, the | | | | | average bitrate | | | | | of this Track | | | | | SHALL be within | | | | | 5% of the given | | | | | value. This | | | | | value is used to | | | | | aid in ABR | | | | | decisions by the | | | | | player. | +-----------------------+---------------+------+--------------------+ | baseUrl | string | N | The base URL of | | | | | this Track. It | | | | | is part of the | | | | | content base URLs | | | | | used to request | | | | | this Track's | | | | | Initialization | | | | | Packets and | | | | | Continuation | | | | | Segments. See | | | | | Section 3.4 for | | | | | more information. | +-----------------------+---------------+------+--------------------+ | codecs | string | N | The definition of | Speelmans Expires 14 October 2023 [Page 38] Internet-Draft HESP April 2023 | | | | the codec(s) | | | | | necessary to | | | | | render the | | | | | content of this | | | | | Track. It MUST | | | | | follow the ISO | | | | | File Format Name | | | | | Space as defined | | | | | by [RFC6381]. If | | | | | this is not | | | | | defined here, | | | | | then it MUST be | | | | | defined by the | | | | | Track's Switching | | | | | Set. | +-----------------------+---------------+------+--------------------+ | continuationPattern | string | N | The URL pattern | | | | | used to request | | | | | Continuation | | | | | Segments | | | | | belonging to this | | | | | Track. The | | | | | pattern needs to | | | | | include the | | | | | {segmentId} | | | | | string; see | | | | | Section 3.4 for | | | | | more information. | | | | | If this is not | | | | | defined here, | | | | | then it MUST be | | | | | defined by the | | | | | Track's Switching | | | | | Set. | +-----------------------+---------------+------+--------------------+ | frameRate | ScaledValue | N | The frame rate of | | | | | this video Track. | | | | | If it is not | | | | | defined by the | | | | | Switching Set, | | | | | then it must be | | | | | defined here. | +-----------------------+---------------+------+--------------------+ | label | string | N | A human-readable | | | | | name for this | | | | | Track. | +-----------------------+---------------+------+--------------------+ | initializationPattern | string | N | The URL pattern | Speelmans Expires 14 October 2023 [Page 39] Internet-Draft HESP April 2023 | | | | used to request | | | | | Initialization | | | | | Packets belonging | | | | | to this media | | | | | Track. The | | | | | pattern needs to | | | | | include the | | | | | {initId} string; | | | | | see Section 3.4 | | | | | for more | | | | | information. If | | | | | this is not | | | | | defined here, | | | | | then it MUST be | | | | | defined by the | | | | | Track's Switching | | | | | Set. | +-----------------------+---------------+------+--------------------+ | mediaTimeOffset | ScaledValue | N | The offset to be | | | | | added to Manifest | | | | | Timestamps to | | | | | calculate Media | | | | | Timestamps | | | | | contained by | | | | | segments of this | | | | | Track. If | | | | | neither the Track | | | | | nor the Switching | | | | | Set has this | | | | | value set, it | | | | | SHALL equal 0. | +-----------------------+---------------+------+--------------------+ | segmentDuration | ScaledValue | N | The duration (in | | | | | seconds) of each | | | | | Segment contained | | | | | by this Track. | | | | | If this value is | | | | | set, then every | | | | | segmentDuration | | | | | seconds, a new | | | | | Segment SHOULD be | | | | | available. More | | | | | information about | | | | | the availability | | | | | is given in | | | | | Section 5.2. If | | | | | not set, then | | | | | each Segment MUST | Speelmans Expires 14 October 2023 [Page 40] Internet-Draft HESP April 2023 | | | | be individually | | | | | defined by the | | | | | segments field. | +-----------------------+---------------+------+--------------------+ Table 14 For any attributes that also exist on VideoSwitchingSetType, if both VideoSwitchingSetType and VideoTrackType have a value for this attribute, then only the value set by VideoTrackType must be considered (except for the identifier and label.) 3.2.14. Resolution A Resolution contains the following elements: +===========+======+==========+=================================+ | Attribute | Type | Required | Description | +===========+======+==========+=================================+ | width | uint | Y | The width of the picture. | +-----------+------+----------+---------------------------------+ | height | uint | Y | The height of the picture. | +-----------+------+----------+---------------------------------+ | sarWidth | uint | N | The width of the sample aspect | | | | | ratio of the resolution. If it | | | | | is not set, it SHALL equal 1. | +-----------+------+----------+---------------------------------+ | sarHeight | uint | N | The height of the sample aspect | | | | | ratio of the resolution. If it | | | | | is not set, it SHALL equal 1. | +-----------+------+----------+---------------------------------+ Table 15 The display aspect ratio belonging to this Resolution can be calculated by using this sample aspect ratio width and height, and the picture width and height as follows: dar = (darWidth, darHeight) darWidth = sarWidth * width darHeight = sarHeight * height 3.2.15. MetadataTrackType This is the type definition of a metadata Track. Speelmans Expires 14 October 2023 [Page 41] Internet-Draft HESP April 2023 +=====================+===============+======+====================+ | Attribute | Type | Req? | Description | +=====================+===============+======+====================+ | id | string | Y | The unique | | | | | identifier for | | | | | this Track. It | | | | | MUST be unique | | | | | within its | | | | | Switching Set. | +---------------------+---------------+------+--------------------+ | segments | SegmentType[] | Y | The metadata of | | | | | the Segments that | | | | | are contained by | | | | | this Track at the | | | | | moment of Manifest | | | | | creation. | | | | | If a segment | | | | | duration is not | | | | | set, then each | | | | | Segment MUST be | | | | | announced by the | | | | | Manifest before it | | | | | is active. More | | | | | information about | | | | | Segment | | | | | availability is | | | | | given in | | | | | Section 5.2. | +---------------------+---------------+------+--------------------+ | startSegmentId | uint | N | The identifier of | | | | | the first Segment | | | | | in the | | | | | Continuation | | | | | Stream of this | | | | | Track. If not | | | | | defined, this | | | | | value SHALL equal | | | | | 0. | +---------------------+---------------+------+--------------------+ | averageBandwidth | uint | N | The average | | | | | bitrate of this | | | | | Track, denoted in | | | | | bits per second. | | | | | It is expected | | | | | that over a | | | | | duration of 10 | | | | | minutes, the | | | | | average bitrate of | Speelmans Expires 14 October 2023 [Page 42] Internet-Draft HESP April 2023 | | | | this Track SHALL | | | | | be within 5% of | | | | | the given value. | | | | | This value is used | | | | | to aid in ABR | | | | | decisions by the | | | | | player. | +---------------------+---------------+------+--------------------+ | bandwidth | uint | N | The peak bitrate | | | | | of this Track. It | | | | | is denoted in bits | | | | | per second. The | | | | | measured bitrates | | | | | of all Segments of | | | | | the Track MUST NOT | | | | | exceed this value. | | | | | This value is used | | | | | to aid in ABR | | | | | decisions by the | | | | | player. | +---------------------+---------------+------+--------------------+ | baseUrl | string | N | The base URL of | | | | | this Track. It is | | | | | part of the | | | | | content base URLs | | | | | used to request | | | | | this Track's | | | | | Continuation | | | | | Segments. See | | | | | Section 3.4 for | | | | | more information. | +---------------------+---------------+------+--------------------+ | codecs | string | N | The definition of | | | | | the codec(s) | | | | | necessary to | | | | | render the content | | | | | of this Track. It | | | | | MUST follow the | | | | | ISO File Format | | | | | Name Space as | | | | | defined by | | | | | [RFC6381]. | +---------------------+---------------+------+--------------------+ | continuationPattern | string | N | The URL pattern | | | | | used to request | | | | | Continuation | | | | | Segments belonging | | | | | to this Track. | Speelmans Expires 14 October 2023 [Page 43] Internet-Draft HESP April 2023 | | | | The pattern needs | | | | | to include the | | | | | {segmentId} | | | | | string; see | | | | | Section 3.4 for | | | | | more information. | | | | | If this is not | | | | | defined here, then | | | | | it MUST be defined | | | | | by the Track's | | | | | Switching Set. | +---------------------+---------------+------+--------------------+ | label | string | N | A human-readable | | | | | name for this | | | | | Track. | +---------------------+---------------+------+--------------------+ | mediaTimeOffset | ScaledValue | N | The offset to be | | | | | added to Manifest | | | | | Timestamps to | | | | | calculate Media | | | | | Timestamps | | | | | contained by | | | | | segments of this | | | | | Track. If neither | | | | | the Track nor the | | | | | Switching Set has | | | | | this value set, it | | | | | SHALL equal 0. | +---------------------+---------------+------+--------------------+ | segmentDuration | ScaledValue | N | The duration (in | | | | | seconds) of each | | | | | Segment contained | | | | | by this Track. If | | | | | this value is set, | | | | | then every | | | | | segmentDuration | | | | | seconds, a new | | | | | Segment SHOULD be | | | | | available. More | | | | | information about | | | | | the availability | | | | | is given in | | | | | Section 5.2. If | | | | | not set, then each | | | | | Segment MUST be | | | | | individually | | | | | defined by the | | | | | segments field. | Speelmans Expires 14 October 2023 [Page 44] Internet-Draft HESP April 2023 +---------------------+---------------+------+--------------------+ Table 16 3.2.16. SegmentType This is the type definition of a Segment. +============+============+==========+==============================+ | Attribute | Type | Required | Description | +============+============+==========+==============================+ | id | uint | Y | The unique identifier for | | | | | this Segment within the | | | | | Track. This identifier | | | | | MUST be incremented by 1 | | | | | for every new Segment of | | | | | the same Track. | +------------+------------+----------+------------------------------+ | timeBounds | TimeBounds | N | The time boundaries of | | | | | this Segment. If this | | | | | Segment's Track does not | | | | | have a constant segment | | | | | duration, then this value | | | | | MUST be set, and the | | | | | Segment's duration MUST | | | | | be available at least 2 | | | | | seconds before the actual | | | | | end of that Segment. | +------------+------------+----------+------------------------------+ Table 17 3.2.17. PresentationEventType Timed metadata events can be embedded in the Manifest by using Presentation Events. Each PresentationEventType contains the following elements: +============+=============================+======+=================+ | Attribute | Type | Req? | Description | +============+=============================+======+=================+ | data | string | Y | The event | | | | | payload. | +------------+-----------------------------+------+-----------------+ | id | string | Y | An unique | | | | | identifier for | | | | | this event. | | | | | It MUST be | Speelmans Expires 14 October 2023 [Page 45] Internet-Draft HESP April 2023 | | | | unique within | | | | | this | | | | | Presentation's | | | | | events. | +------------+-----------------------------+------+-----------------+ | timeBounds | PresentationEventTimeBounds | Y | The time | | | | | boundaries for | | | | | the event, | | | | | during which | | | | | the event | | | | | SHALL be | | | | | active. | +------------+-----------------------------+------+-----------------+ | encoding | Enum("identity", "base64", | N | The content | | | "json") | | encoding of | | | | | the event | | | | | data. identity | | | | | signifies that | | | | | the encoding | | | | | is plaintext. | | | | | base64 | | | | | signifies | | | | | Base64 | | | | | encoding. json | | | | | signifies that | | | | | the payload | | | | | given by data | | | | | is a valid | | | | | JSON document. | | | | | If this JSON | | | | | document is | | | | | not valid, | | | | | this event | | | | | MUST be | | | | | ignored. If | | | | | not set, the | | | | | encoding SHALL | | | | | default to | | | | | identity. | +------------+-----------------------------+------+-----------------+ Table 18 3.2.18. PresentationEventTimeBounds The time boundaries of a PresentationEventType are defined as follows: Speelmans Expires 14 October 2023 [Page 46] Internet-Draft HESP April 2023 +=================+======+==========+==============================+ | Attribute | Type | Required | Description | +=================+======+==========+==============================+ | startTimeOffset | uint | N | The scaled start time offset | | | | | of the event, defined in | | | | | seconds divided by the | | | | | timescale. The actual start | | | | | time of the event can be | | | | | calculated by dividing this | | | | | value by the scale and | | | | | adding the resulting value | | | | | to the start time of the | | | | | Presentation. It is defined | | | | | as seconds divided by the | | | | | timescale. If it is not | | | | | set, it SHALL equal 0. | +-----------------+------+----------+------------------------------+ | duration | uint | N | The scaled duration of the | | | | | event, defined in seconds | | | | | divided by the timescale. | | | | | If it is not set, it SHALL | | | | | equal 0. | +-----------------+------+----------+------------------------------+ | scale | uint | N | The timescale used for these | | | | | time bounds. If it is not | | | | | set, it SHALL be equal to 1. | +-----------------+------+----------+------------------------------+ Table 19 3.3. Manifest requests The Manifest SHOULD be available through an HTTP GET request. The URL of this Manifest can be personalized by the user. +==================================+========+==================+ | Request path | Method | Summary | +==================================+========+==================+ | (chosen by the stream publisher) | GET | Retrieve the | | | | stream Manifest. | +----------------------------------+--------+------------------+ Table 20: Manifest Requests Speelmans Expires 14 October 2023 [Page 47] Internet-Draft HESP April 2023 3.3.1. Manifest responses +==============+========================================+ | Success | | +==============+========================================+ | Status code | 200 | +--------------+----------------------------------------+ | Content-Type | JSON (MIME type MUST equal | | | application/vnd.theo.hesp+json) | +--------------+----------------------------------------+ | Description | When the given Manifest exists on the | | | server, the Manifest data is returned. | +--------------+----------------------------------------+ Table 21: Manifest Responses: Success +=============+==================================================+ | Status code | Description | +=============+==================================================+ | 404 | The Manifest is not available for the given URL. | +-------------+--------------------------------------------------+ Table 22: Manifest Responses: Error If an error occurs, the player SHOULD attempt to retry the request. In case of consecutive unsuccessful requests, the media player SHOULD assume the content is unavailable and cease playback. 3.4. Addressing of content requests Several elements of the Manifest contain a baseUrl attribute. These attributes are used to construct the URLs of media content (and metadata.) 3.4.1. Content request URL resolution A content request URL for a specific Track SHALL be constructed by applying relative resolution (as explained in Section 5.2 of RFC 3986 [RFC3986]) to each defined baseUrl or contentBaseUrl attribute relating to that Track, starting from the root of the Manifest. The URL of the Manifest SHALL be used as a base for the first resolution, after which the target URL of the previous resolution SHALL be used as the base URL of the next resolution. This means that the content request URL for a Track's Initialization Stream is constructed as follows (in pseudocode): Speelmans Expires 14 October 2023 [Page 48] Internet-Draft HESP April 2023 T = manifestUrl if isDefined(Manifest.contentBaseUrl): T = resolve(Manifest.contentBaseUrl, T) if isDefined(Presentation.baseUrl): T = resolve(Presentation.baseUrl, T) if isDefined(SwitchingSet.baseUrl): T = resolve(SwitchingSet.baseUrl, T) if isDefined(Track.baseUrl): T = resolve(Track.baseUrl, T) contentRequestURL = resolve(initializationPattern, T) where initializationPattern is the attribute given by either SwitchingSet or Track (with Track taking precedence if given by both) and resolve(R, B) is relative resolution, where R is a URI reference and B is a base URI. The content request URL for the Track's Continuation Stream can be constructed in the same manner if the initializationPattern is replaced with the continuationPattern. Both URLs MUST be unique for each unique Track. An example of content addressing is given in Appendix A.1.3. 3.4.2. Requesting using an identifier and the content request URL The content request URL MUST include the {initId} pattern for Initialization Stream URLs and the {segmentId} pattern for Continuation Stream URLs. These patterns are replaced in the actual content requests: {initId} is replaced with the requested Sequence Number of the Initialization Stream, and {segmentId} is replaced with the requested segment identifier of the Continuation Stream. In order to add leading zeros to the identifier, the following can be added to the patterns initId and segmentId: :0(n)d where (n) is the minimal amount of characters the resulting identifier has (if the identifier is already longer, it will not be altered.) For example, for a continuation segment with identifier 100, a following content request URL https://www.example.com/s-1/ content-{segmentId:06d}.mp4 will resolve to https://www.example.com/ s-1/content-000100.mp4. While the content request URL https://www.example.com/s-1/content-{segmentId:02d}.mp4 resolves to https://www.example.com/s-1/content-100.mp4 Further details about these requests are given in Section 4 and Section 5. Speelmans Expires 14 October 2023 [Page 49] Internet-Draft HESP April 2023 3.5. Manifest example A full Manifest example, together with information on content addressing and timing information, is given by Appendix A.1. 4. Initialization Stream The player uses the information in the HESP Manifest to fetch an Initialization Packet. 4.1. Initialization Stream purpose The Initialization Stream is a stream containing only independent samples. This stream is not regularly used by a single client nor completely streamed. The purpose of the Initialization Stream is to make available, upon request of the client, the separate independent frames packaged in an Initialization Packet. This way, a client has more control over the specific position of the stream where it wants to initiate playback. For example, it allows for more granularity when starting playback at the live edge, seeking a specific point in time, or switching to an alternative Track. Additionally, the Initialization Packet contains information on the position of the following frame in the Continuation Stream to achieve regular media playback. 4.2. Initialization Packet format 4.2.1. Video Initialization Packet A video Initialization Packet MUST contain: * A CMAF header, i.e., all information required to initialize the media decoder, stored in ISO Base Media File Format [ISOBMFF] boxes as specified by CMAF [CMAF]. The minimal required contents are defined in Section 4.2.4 * An additional in-band metadata event containing extra HESP information, included in the aforementioned CMAF segment. The definition of such an event is denoted in Section 4.2.5. * A CMAF segment, i.e., a group of one or more media samples, starting with at least one independent media sample, and timing information related to these samples, stored in ISOBMFF [ISOBMFF] boxes as specified by CMAF [CMAF]. Speelmans Expires 14 October 2023 [Page 50] Internet-Draft HESP April 2023 4.2.2. Audio Initialization Packet An audio Initialization Packet MUST contain: * A CMAF header, i.e., all information required to initialize the media decoder, stored in ISO Base Media File Format [ISOBMFF] boxes as specified by CMAF [CMAF]. The minimal required contents are defined below. * An additional in-band metadata event containing extra HESP information, included in the aforementioned CMAF segment. The definition of such an event is denoted below. It MAY also contain an independent (audio) media sample, as is defined by the video Initialization Packet. However, it is heavily discouraged as it leads to more storage costs for the provider without any significant advantage. 4.2.3. Constraint on media information In order to avoid any decoder anomalies, a HESP stream MUST follow the following constraint: * When the media sample(s) contained in an Initialization Packet are concatenated with the samples contained in the corresponding Continuation Segment with the referenced index, starting as of the referenced offset, the resulting bitstream should be compliant to the codec limitations. 4.2.4. CMAF header A CMAF header is defined in ISO/IEC 23000-19:2020 [CMAF] as: "a sequence of CMAF constrained ISOBMFF boxes that do not reference any media samples (3.3.15), but are associated with a CMAF track (3.2.1) and necessary for the decoding of its CMAF fragments (3.1.1)." As such, the header MUST NOT contain any samples. This means that for the ISO Base Media File Format, at least the following boxes MUST be given: * An ftyp box. * A moov box. * One or more tracks and accompanying boxes, though stbl and other related boxes cannot give information about any actual sample entries. Speelmans Expires 14 October 2023 [Page 51] Internet-Draft HESP April 2023 4.2.5. Event message information In order to pass information about the Continuation Stream, an in- band event in the form of an emsg box must be added to the Initialization Packet. The format of this box is defined at Section 6.2.1.1. The message_data field MUST contain the following two values (see Table 33): * the Continuation Segment index (index), which defines the index of the Continuation Segment containing the next media sample. * the Continuation Segment byte offset (offset), which defines the position of the next media sample in the Continuation Segment. This field is OPTIONAL if the next media sample is located at the start of the segment, in which case a byte-range request is not needed. The message_data field of the emsg box could for example look like this: {"index":1,"offset":1234} 4.3. Initialization Stream addressing Section 3.4 defines how to create the correct URLs and how to request Initialization Packets. The request content URL is used together with the desired Sequence Number to retrieve an Initialization Packet. Additionally, {initId} can also be replaced with the string now. If this URL is requested, the most recently available Initialization Packet MUST be returned. 4.3.1. Initialization Stream requests Initialization Packets MUST be available through a basic GET request. They MUST be able to be retrieved through two methods: Speelmans Expires 14 October 2023 [Page 52] Internet-Draft HESP April 2023 +========================+========+============================+ | Request path | Method | Summary | +========================+========+============================+ | Initialization content | GET | Retrieve the most recent | | request URL | | Initialization Packet from | | {initId} is replaced | | the given track. | | with the string now | | | +------------------------+--------+----------------------------+ | Initialization content | GET | Retrieve the | | request URL | | Initialization Packet with | | {initId} is replaced | | the given Sequence Number | | with a Sequence Number | | from the given track. | +------------------------+--------+----------------------------+ Table 23: Initialization Stream requests 4.3.2. Initialization Stream responses +==============+================================================+ | Success | | +==============+================================================+ | Status Code | 200 | +--------------+------------------------------------------------+ | Content-Type | MUST match the mimeType given by the Stream's | | | Switching Set (see Section 3 for more details) | +--------------+------------------------------------------------+ | Description | Return the requested Initialization Packet | | | when it exists on the media server. | +--------------+------------------------------------------------+ Table 24: Initialization Stream responses: success +========+============================================+ | Status | Description | | code | | +========+============================================+ | 404 | The Track does not exist on the media | | | server, or the requested Initialization | | | Packet does not exist on the media server. | +--------+--------------------------------------------+ Table 25: Initialization Stream responses: error Speelmans Expires 14 October 2023 [Page 53] Internet-Draft HESP April 2023 5. Continuation Stream The client uses the information given by the Manifest and the Initialization Packet to request the Continuation Stream. This low latency stream is used for the bulk of media playback of HESP. The Continuation Stream is an independently playable CMAF stream. 5.1. Continuation Stream format 5.1.1. Media content The Continuation Stream is packaged as a regular CMAF stream, albeit with some encoding constraints, depending on the chosen profile (see Appendix C.) Maximum Gain Profile * Samples MUST only contain references to the one sample preceding it. * Each CMAF chunk MUST contain at most one sample (for the lowest possible latency.) * Long CMAF Segments (values of multiple minutes are possible.) Compatibility Profile * Regular sized CMAF Segments (recommendation: between 1 and 30 seconds) * Chunk sizes range between one sample and one sub-GOP * The following GOP structure MUST be followed: I B ... B P B ... B P B ... B P * The number of B frames MAY vary from 0 (same behavior as Maximum Gain Profile) to 4 (recommended maximum) * Each sub-GOP (B ... B P) MUST only reference one previous frame (allowing injection of keyframes) 5.2. Continuation Segment availability Continuation Segments must together create a continuous stream of media data. There MUST NOT exist gaps in the time boundaries of subsequent Continuation Segments. Speelmans Expires 14 October 2023 [Page 54] Internet-Draft HESP April 2023 There exist two ways to signal Segment availability. Either the Track has a segmentDuration set in the Manifest, which represents the constant duration of each Segment. In this case, a client can derive on its own when to start requesting a new Segment. A new Segment SHOULD be published every n seconds, where n equals segmentDuration. This new Segment MUST become available within 100 milliseconds from that point. It is not allowed to drift, i.e., if a Segment is only published at n+100ms, then the next Segment MUST be available at 2n+100ms at the latest. The duration of the last Segment of a Track MAY be shorter than this constant segmentDuration. As a new Manifest must be retrieved near the end of a Presentation, a client should be able to start requesting content of the new Presentation in a timely manner, regardless of the length of this last Segment. The other option is for the Track to specify all its Segments outright in the segments field of the Manifest. As the Manifest does not get regularly retrieved, it is REQUIRED to signal a Manifest update (see Section 6.2.1.2) at the end of each Segment. It is recommended only to use this option in the "Maximum Gain Profile", as it can otherwise significantly increase the number of Manifest requests necessary. 5.3. Continuation Stream addressing To start playback of a Track, a client MUST request the Continuation Segments of the chosen Track(s) using the information given by (already obtained) the Manifest and Initialization Packet. Requests for Content Segments should be made using HTTP GET requests. The first request, following an Initialization Packet, fetches the Segment indicated by the Initialization Packet. A byte-range header should be used to specify the range of data that needs to be requested. This information is also given by the Initialization Packet. A client then automatically calculates the URL of the next Segment as it is indicated in the Manifest and requests the next Segment using a regular HTTP GET request. 5.3.1. Continuation Stream URLs Section 3.4 defines how to create the correct URLs and how to request a continuation segment. The request content URL is used together with the desired segment identifier to retrieve the Segment. Speelmans Expires 14 October 2023 [Page 55] Internet-Draft HESP April 2023 5.3.2. Continuation Stream requests Suppose a client needs to request a partial Continuation Segment, for example, starting at the byte offset given by metadata of an Initialization Packet. In that case, it MUST use one or more HTTP Range [RFC7233] Requests. The start and end of the range of each request MUST be defined. Often, the total length of the Continuation Segment will not yet be known at the time of the request. If a client cannot define an accurate end value for the HTTP Range of a request, then 2^53 - 1 (9007199254740991) SHOULD be used. +===========================+========+===========================+ | Request path | Method | Summary | +===========================+========+===========================+ | Continuation content | GET | Retrieve the Continuation | | request URL | | Segment with the | | {segmentId} is replaced | | requested identifier from | | with a segment identifier | | the given track. | +---------------------------+--------+---------------------------+ Table 26: Continuation Stream requests 5.3.3. Continuation Stream responses A distinction is made between how responses should be returned, depending on the version of the HTTP protocol used. 5.3.3.1. HTTP/1.1 successful response If an HTTP Range request is sent, then a 206 Partial Content response MUST be returned upon a successful response. The response MUST use Chunked Transfer Coding [RFC7230] to ensure timely delivery of media data. Speelmans Expires 14 October 2023 [Page 56] Internet-Draft HESP April 2023 +===================+==========================================+ | Success | | +===================+==========================================+ | Status Code | 206 | +-------------------+------------------------------------------+ | Content-Type | MUST match the mimeType given by the | | | Stream's Switching Set (see Section 3 | | | for more details) | +-------------------+------------------------------------------+ | Transfer-Encoding | chunked | +-------------------+------------------------------------------+ | Description | The requested range of Segment data is | | | returned from the server. Depending on | | | the byte-range requested, the connection | | | is kept open to retrieve live data. | +-------------------+------------------------------------------+ Table 27: Continuation Stream responses: success (Range header is given) For requests without a Range header, a 200 OK response MUST be returned upon success. +===================+========================================+ | Success | | +===================+========================================+ | Status Code | 200 | +-------------------+----------------------------------------+ | Content-Type | MUST match the mimeType given by the | | | Stream's Switching Set (see Section 3 | | | for more details) | +-------------------+----------------------------------------+ | Transfer-Encoding | chunked | +-------------------+----------------------------------------+ | Description | The Segment data is returned from the | | | server. Depending on the availability | | | of the Segment, the connection is kept | | | open to retrieve live data. | +-------------------+----------------------------------------+ Table 28: Continuation Stream responses: success (Range header is not given) 5.3.3.2. HTTP/2 successful response HTTP/2 uses frame-based transmission and cannot use Chunked Transfer Coding. As such, this header is not given here. Speelmans Expires 14 October 2023 [Page 57] Internet-Draft HESP April 2023 +==============+==========================================+ | Success | | +==============+==========================================+ | Status code | 206 | +--------------+------------------------------------------+ | Content-Type | MUST match the mimeType given by the | | | Stream's Switching Set (see Section 3 | | | for more details) | +--------------+------------------------------------------+ | Description | The requested range of Segment data is | | | returned from the server. Depending on | | | the byte-range requested, the connection | | | is kept open to retrieve live data. | +--------------+------------------------------------------+ Table 29: Continuation Stream responses: success (Range header is given) For requests without a Range header, a 200 OK response MUST be returned upon success. +==============+===================================================+ | Success | | +==============+===================================================+ | Status code | 200 | +--------------+---------------------------------------------------+ | Content-Type | MUST match the mimeType given by the Stream's | | | Switching Set (see Section 3 for more details) | +--------------+---------------------------------------------------+ | Description | The Segment data is returned from the server. | | | Depending on the availability of the Segment, the | | | connection is kept open to retrieve live data. | +--------------+---------------------------------------------------+ Table 30: Continuation Stream responses: success (Range header is not given) 5.3.3.3. Response errors +========+=======================================================+ | Status | Description | | code | | +========+=======================================================+ | 404 | The Track does not exist on the media server, or the | | | requested Segment does not exist on the media server. | +--------+-------------------------------------------------------+ | 416 | The requested byte-range could not be fulfilled. | +--------+-------------------------------------------------------+ Speelmans Expires 14 October 2023 [Page 58] Internet-Draft HESP April 2023 Table 31: Continuation Stream responses: error 6. Timed metadata HESP supports timed metadata through two methods: metadata Tracks for continuous, often segmented metadata and metadata events for sporadic metadata updates. 6.1. Metadata Tracks Metadata Tracks function similarly to media Tracks, however, without the need for an Initialization Stream. The attributes for metadata Tracks in the Manifest can be found at Section 3.2.15. The addressing happens similarly to the addressing of Continuation segments: a continuationPattern is given for each metadata Track, either directly set on the Track or on the Switching Set of the Track. Each metadata Segment contains a numerical identifier that increments by one for each new Segment of the Track. This identifier, together with the addressing pattern, creates the URL used to retrieve the contents of the Segment. The Manifest contains the duration of each metadata Segment, either stated individually per Segment or through the segmentDuration attribute set on the metadata Track. It is possible that chunked encoding is used here to ensure that the contents are delivered as soon as possible, but this is not a requirement. This can be useful for subtitles alongside live content, for example. 6.2. Metadata events Metadata events can be used to signal information that does not become available in regular intervals. These events can either be transmitted in-band, where it MUST be added to the video or audio Continuation Streams, or out-of-band, in which case details about the metadata event MUST be available in the Manifest. 6.2.1. In-band events In order to deliver events in-band, root-level Event Message (emsg) boxes MUST be added to ongoing media Continuation Streams. The definition of an emsg box can be found in the CMAF [CMAF] specification. These boxes should be appended to each Track of a Presentation to ensure all viewers can receive such an event. It is recommended to use out-of-band events if the included data is significantly large. Speelmans Expires 14 October 2023 [Page 59] Internet-Draft HESP April 2023 The HESP specification defines a few in-band events that it leverages for client initialization and Manifest updates. The structure of these events is given below. 6.2.1.1. Initialization data This event is appended to each Initialization Packet for the client to request the correct Continuation Segments. It is an ´ (U+00B4)emsg´ (U+00B4) box with the following REQUIRED values: +=========================+==================================+ | Attribute | Value | +=========================+==================================+ | version | 0 | +-------------------------+----------------------------------+ | scheme_id_uri | "urn:theo:hesp:2020" | +-------------------------+----------------------------------+ | value | "initdata" | +-------------------------+----------------------------------+ | timescale | MUST match the timescale of the | | | Initialization Packet in case of | | | video or MUST equal 1 otherwise. | +-------------------------+----------------------------------+ | presentation_time_delta | 0 | +-------------------------+----------------------------------+ | event_duration | MUST match the duration of the | | | Initialization Packet in case of | | | video or MUST equal 0 otherwise. | +-------------------------+----------------------------------+ | id | can be freely set (and MUST be | | | ignored by the player) | +-------------------------+----------------------------------+ | message_data | MUST contain the data defined by | | | Table 33, formatted as JSON | +-------------------------+----------------------------------+ Table 32: emsg box containing an initialization data event Speelmans Expires 14 October 2023 [Page 60] Internet-Draft HESP April 2023 +===========+=========+==========+================================+ | Attribute | Type | Required | Description | +===========+=========+==========+================================+ | index | integer | Y | The Continuation Segment index | | | | | (see Section 4.2.5.) | +-----------+---------+----------+--------------------------------+ | offset | integer | N | The Continuation Segment byte | | | | | offset (see Section 4.2.5), it | | | | | SHALL be 0 if not given here. | +-----------+---------+----------+--------------------------------+ Table 33: message_data contents of an initialization data event 6.2.1.2. Manifest update This event is used to signal the client that a new Manifest must be retrieved. This can occur for many reasons, such as before a Presentation change, availability of new out-of-band metadata, etc. It is an emsg box with the following REQUIRED values: +=========================+================================+ | Attribute | Value | +=========================+================================+ | version | 0 | +-------------------------+--------------------------------+ | scheme_id_uri | "urn:theo:hesp:2020" | +-------------------------+--------------------------------+ | value | "manifestupdate" | +-------------------------+--------------------------------+ | timescale | 1 | +-------------------------+--------------------------------+ | presentation_time_delta | 0 | +-------------------------+--------------------------------+ | event_duration | 0 | +-------------------------+--------------------------------+ | id | MAY be freely set (and MUST be | | | ignored by the player) | +-------------------------+--------------------------------+ | message_data | MUST contain the data defined | | | by Table 35, formatted as JSON | +-------------------------+--------------------------------+ Table 34: emsg box containing a Manifest update event Speelmans Expires 14 October 2023 [Page 61] Internet-Draft HESP April 2023 +===========+========+==========+===========================+ | Attribute | Type | Required | Description | +===========+========+==========+===========================+ | url | string | N | the URL of an alternative | | | | | location of the Manifest | +-----------+--------+----------+---------------------------+ Table 35: message_data contents of a Manifest data event If the event contains a URL, then this Manifest request MUST be made to this address. Further Manifest requests do not have this requirement. 6.2.2. Out-of-band events Out-of-band events can be added to the Manifest through Presentation Events. The definition of a Presentation Event is given in Section 3.2.17. The contents of the event data are not predefined. It is possible to include arbitrary data as Base64 encoded data, and plaintext data can be included as-is. If needed, the data can be an URL that needs to be resolved separately, but this is up to the publisher of this data. 7. Content protection HESP has support for content protection. It allows DRM systems to be implemented through the common encryption standard. 7.1. Common encryption support As HESP has the requirement for media to be structured as ISOBMFF [ISOBMFF], common encryption [CENC] is to be used to encrypt that media content. Common encryption specifies 4 protection schemes that may be used: cenc, cbc1, cens and cbcs. For HESP, either the AES-CBC subsample pattern encryption scheme (cbcs) or the AES-CTR full sample pattern encryption scheme (cenc) MUST be used. 7.2. HESP Manifest The HESP Manifest has a SwitchingSetProtection structure to set up common encryption for audio and video Switching Sets. The definition of this structure can be found in Chapter 3. As a result of this being set on a Switching Set level: Speelmans Expires 14 October 2023 [Page 62] Internet-Draft HESP April 2023 * All Tracks belonging to such a Switching Set MUST be encrypted with the same content key. Aligned Switching Sets can be used to ensure that a client can still switch through Tracks of different Switching Sets. * Audio and video data SHOULD be encrypted with different content keys. This is a recommendation as both often have different encryption strength requirements. The SwitchingSetProtection structure MAY contain a ProtectionSystemSpecificHeaderBox (pssh), which can also be contained by the Initialization Stream. Note that this box MUST be given by at least one of both options in order for a license request to be made. If both exist for a Switching Set, the pssh box from the Initialization Stream MUST be disregarded. This allows for more straightforward alterations of license information after a stream has been created or published. 7.3. CMAF box structure The media of a protected stream needs to contain certain ISOBMFF boxes to be compliant with CENC (and CMAF). HESP requires the same boxes to be present in media streams. A brief overview of these boxes is given below. More information on this requirement can be found in the CENC [CENC] and CMAF [CMAF] specifications. 7.3.1. Initialization Stream Initialization Packets MUST contain the following boxes: * TrackEncryptionBox (tenc): This box contains default parameters regarding sample encryption. * SchemeTypeBox (schm): This box identifies the protection scheme. scheme_type MUST be set to cbcs or cenc. * ProtectionSystemSpecificHeaderBox (pssh): If the Manifest does not contain a pssh box that applies to this Track, then this box MUST be included in each Initialization Packet of each Track of the protected Switching Set. If the Manifest does contain a pssh box that applies to this Track, then this box MUST be disregarded. In order to signal that the Track is encrypted, the stream type MUST equal encv for video Tracks and enca for audio Tracks. Additionally, video Initialization Packets contain a sample. If that sample is encrypted, then the same requirements for CMAF fragments of a Continuation Segment also apply here: a senc box MUST be included, pssh, saiz and saio boxes MAY be included. The following section contains more information about these requirements. Speelmans Expires 14 October 2023 [Page 63] Internet-Draft HESP April 2023 7.3.2. Continuation Stream CMAF fragments of a Continuation Segment MUST contain the following box: * SampleEncryptionBox (senc): This box is used to store initialization vector data and information on subsample encryption. As each chunk in HESP must currently contain at most one sample, sample_count SHALL always 1. The following boxes MAY be included: * ProtectionSystemSpecificHeaderBox (pssh): If any updates need to be made to the underlying licensing system, a pssh box MAY be included. * SampleAuxiliaryInformationSizesBox (saiz): This box is used to store the size of per-sample auxiliary information. It is only REQUIRED if such per-sample information exists. * SampleAuxiliaryInformationOffsetsBox (saio): This box is used to store the offsets of per-sample auxiliary information. It is only REQUIRED if such per-sample information exists. 8. Contributors Significant contributions to the design of this protocol were made by Egon Okerman, Samie Beheydt, and Johan Vounckx. 9. IANA Considerations This memo requests that the following MIME type [RFC2046] be registered with the IANA: | Type name: application | | Subtype name: vnd.theo.hesp+json | | Required parameters: (none) | | Optional parameters: (none) | | Encoding considerations: encoded as text. | | Security considerations: See Section 10. | | Compression: this media type does not employ compression. | Speelmans Expires 14 October 2023 [Page 64] Internet-Draft HESP April 2023 | Interoperability considerations: There are no byte-ordering | issues, since files are 7- or 8-bit text. Applications could | encounter unrecognized tags, which SHOULD be ignored. 10. Security Considerations Since the protocol uses HTTP to transmit data, the regular HTTP security considerations apply. See section 15 of RFC 7230 [RFC7230]. Clients SHOULD take care when parsing files received from a server so that non-compliant files are rejected. Clients SHOULD range-check responses to prevent buffer overflows. See also the Security Considerations section of RFC 3986 [RFC3986]. Clients SHOULD load resources identified by URI lazily to avoid contributing to denial- of-service attacks. HTTP requests often include session state ("cookies"), which may contain private user data. Implementations MUST follow cookie restriction and expiry rules specified by RFC 6265 [RFC6265]. See also the Security Considerations section of RFC 6265, and RFC 2964 [RFC2964]. Encryption keys are specified by URI. The delivery of these keys SHOULD be secured by a mechanism such as HTTP over TLS [RFC8446] (formerly SSL) in conjunction with a secure realm or a session cookie. 11. Normative References [CENC] International Organization for Standardization, "Information technology - MPEG systems technologies - Part 7: Common encryption in ISO base media file format files", December 2020, . [CMAF] International Organization for Standardization, "Information technology - Multimedia application format (MPEG-A) - Part 19: Common media application format (CMAF) for segmented media", March 2020, . [DASH] International Organization for Standardization, "Information technology — Dynamic adaptive streaming over HTTP (DASH) — Part 1: Media presentation description and segment formats", December 2019, . Speelmans Expires 14 October 2023 [Page 65] Internet-Draft HESP April 2023 [I-D.pantos-hls-rfc8216bis] Pantos, R., "HTTP Live Streaming 2nd Edition", Work in Progress, Internet-Draft, draft-pantos-hls-rfc8216bis-12, 11 November 2022, . [ISO6392] International Organization for Standardization, "Codes for the representation of names of languages - Part 2: Alpha-3 code", November 1998, . [ISO8601] International Organization for Standardization, "Date and time - Representations for information interchange", February 2019, . [ISOBMFF] International Organization for Standardization, "Information technology - Coding of audio-visual objects - Part 12: ISO base media file format", December 2020, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2964] Moore, K. and N. Freed, "Use of HTTP State Management", BCP 44, RFC 2964, DOI 10.17487/RFC2964, October 2000, . [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, DOI 10.17487/RFC6265, April 2011, . [RFC6381] Gellens, R., Singer, D., and P. Frojdh, "The 'Codecs' and 'Profiles' Parameters for "Bucket" Media Types", RFC 6381, DOI 10.17487/RFC6381, August 2011, . [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014, . Speelmans Expires 14 October 2023 [Page 66] Internet-Draft HESP April 2023 [RFC7233] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Range Requests", RFC 7233, DOI 10.17487/RFC7233, June 2014, . [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . [UUID] International Organization for Standardization, "Information technology - Procedures for the operation of object identifier registration authorities - Part 8: Generation of universally unique identifiers (UUIDs) and their use in object identifiers", August 2014, . 12. Informative References [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, DOI 10.17487/RFC2046, November 1996, . Appendix A. Example usage A.1. Manifest For the initial step, the client retrieves a Manifest. A.1.1. Retrieving the Manifest The URL of the Manifest is given out of band to the client. The client sends out a GET request. In this case, let's suppose the Manifest is available at https://example.com/stream1/manifest.json. The client then makes such a request: GET /stream1/manifest.json HTTP/1.1 Host: example.com Accept: application/vnd.theo.hesp+json The server responds with the following headers: Speelmans Expires 14 October 2023 [Page 67] Internet-Draft HESP April 2023 HTTP/1.1 200 OK Content-Type: application/vnd.theo.hesp+json; charset=utf-8 Content-Length: 6867 Date: Wed, 31 Mar 2021 08:00:00 GMT and the following body: { "activePresentation":"1", "availabilityDuration":{ "value":2400 }, "creationDate":"2021-03-31T08:00:00.000Z", "fallbackPollRate":300, "manifestVersion":"2.0.0", "streamType":"live", "currentTime":{ "value":1134000000, "scale":90000 }, "presentations":[ { "id":"0", "timeBounds":{ "startTime":0, "endTime":972000000, "scale":90000 }, "audio":[ { "id":"main-audio", "language":"eng", "baseUrl":"audio/", "channels":2, "codecs":"mp4a.40.2", "continuationPattern":"content-{segmentId}.mp4", "initializationPattern":"init-{initId}.mp4", "sampleRate":48000, "tracks":[ { "id":"96kbps", "averageBandwidth":96000, "bandwidth":96000, "baseUrl":"96k/", "segmentDuration":{ "value":540000, "scale":90000 }, Speelmans Expires 14 October 2023 [Page 68] Internet-Draft HESP April 2023 "segments":[ { "id":1799, "timeBounds":{ "startTime":971460000, "scale":90000 } } ] } ] } ], "video":[ { "id":"main-video", "baseUrl":"video/", "frameRate":{ "value":25 }, "continuationPattern":"content-{segmentId}.mp4", "initializationPattern":"init-{initId}.mp4", "tracks":[ { "id":"720p", "bandwidth":3000000, "baseUrl":"720p/", "codecs":"avc1.4d001f", "resolution":{ "width":1280, "height":720 }, "segmentDuration":{ "value":540000, "scale":90000 }, "segments":[ { "id":1799, "timeBounds":{ "startTime":971460000, "scale":90000 } } ] } ] } Speelmans Expires 14 October 2023 [Page 69] Internet-Draft HESP April 2023 ] }, { "id":"1", "timeBounds":{ "startTime":972000000, "scale":90000 }, "baseUrl":"https://otherexample.com/s2/", "audio":[ { "id":"main-audio", "language":"eng", "baseUrl":"audio/", "channels":2, "codecs":"mp4a.40.2", "sampleRate":48000, "mediaTimeOffset":{ "value":-972000000, "scale":90000 }, "tracks":[ { "id":"128kbps", "averageBandwidth":128000, "bandwidth":128000, "continuationPattern": "128k-content-{segmentId}.mp4", "initializationPattern": "128k-init-{initId}.mp4", "segmentDuration":{ "value":540000, "scale":90000 }, "segments":[ { "id":300, "timeBounds":{ "startTime":1134000000, "scale":90000 } } ] } ] } ], "video":[ Speelmans Expires 14 October 2023 [Page 70] Internet-Draft HESP April 2023 { "id":"main-video", "baseUrl":"video/", "frameRate":{ "value":25 }, "mediaTimeOffset":{ "value":-972000000, "scale":90000 }, "tracks":[ { "id":"720p", "bandwidth":3000000, "codecs":"avc1.4d001f", "continuationPattern": "720p-content-{segmentId}.mp4", "initializationPattern": "720p-init-{initId}.mp4", "resolution":{ "width":1280, "height":720 }, "segmentDuration":{ "value":540000, "scale":90000 }, "segments":[ { "id":300, "timeBounds":{ "startTime":1134000000, "scale":90000 } } ] }, { "id":"1080p", "bandwidth":5000000, "codecs":"avc1.4d001f", "continuationPattern": "1080p-content-{segmentId}.mp4", "initializationPattern": "1080p-init-{initId}.mp4", "resolution":{ "width":1920, "height":1080 Speelmans Expires 14 October 2023 [Page 71] Internet-Draft HESP April 2023 }, "segmentDuration":{ "value":540000, "scale":90000 }, "segments":[ { "id":300, "timeBounds":{ "startTime":1134000000, "scale":90000 } } ] } ] } ] } ] } A.1.2. Timing information In the above Manifest, we have two Presentations: * The first Presentation with ID "0" is not active at the current time, though it was active previously. It contains one audio Track and one video Track. It is 3 hours long in total and starts at 00:00:00.000 (Manifest Timestamp.) No Track has a mediaTimeOffset defined, so the Manifest Timestamps match the Media Timestamps. * The second Presentation with ID "1" is active at the current time. It contains one audio Track and two video Tracks. Its total duration is yet to be defined. Its start time is 03:00:00.000 in Manifest Time and its current time (at the moment the Manifest was retrieved) is 03:30:00.000. All Tracks have the same mediaTimeOffset defined. The Media Timestamps for this Presentation start at 00:00:00.000. That also means that for all the currently active Segments, the media data will contain a starting timestamp of 00:30:00.000. The availabilityDuration of the Manifest is 40 minutes. As only 30 minutes of the second Presentation have elapsed, some Segments of the first Presentation are still available. Therefore, the first Presentation must still be included in the Manifest. Once 10 minutes have passed, the first Presentation can be left out of the Manifest. Speelmans Expires 14 October 2023 [Page 72] Internet-Draft HESP April 2023 A.1.3. Content addressing The client uses the Manifest to derive the content request URLs of each Track. For the audio Track of the first Presentation, the following parts are found: AudioSwitchingSet.baseUrl = "audio/" AudioTrack.baseUrl = "96k/" AudioSwitchingSet.initializationPattern = "init-{initId}.mp4" AudioSwitchingSet.continuationPattern = "content-{segmentId}.mp4" The Manifest URL (https://example.com/stream1/manifest.json) is used as the base for resolution, and then relative resolution is applied to each of the parts above. T = resolve(AudioSwitchingSet.baseUrl, manifestUrl) = "https://example.com/stream1/audio/" T = resolve(AudioTrack.baseUrl, T) = "https://example.com/stream1/audio/96k/" initBaseUrl = resolve(AudioSwitchingSet.initializationPattern, T) = "https://example.com/stream1/audio/96k/init-{initId}.mp4" contBaseUrl = resolve(AudioSwitchingSet.continuationPattern, T) = "https://example.com/stream1/audio/96k/content-{segmentId}.mp4" The final content request URLs are https://example.com/stream1/audio/96k/init-{initId}.mp4 and https://example.com/stream1/audio/96k/content-{segmentId}.mp4 for the Initialization Stream and Continuation Stream respectively. For the audio Track of the second Presentation, the following parts are found: Presentation.baseUrl = "https://otherexample.com/s2/" AudioSwitchingSet.baseUrl = "audio/" AudioTrack.initializationPattern = "128k-init-{initId}.mp4" AudioTrack.continuationPattern = "128k-content-{segmentId}.mp4" The Manifest URL (https://example.com/stream1/manifest.json) is used as the base for resolution, and then relative resolution is applied to each of the parts above. Speelmans Expires 14 October 2023 [Page 73] Internet-Draft HESP April 2023 T = resolve(Presentation.baseUrl, manifestUrl) = "https://otherexample.com/s2/" T = resolve(AudioSwitchingSet.baseUrl, T) = "https://otherexample.com/s2/audio/" initBaseUrl = resolve(AudioTrack.initializationPattern, T) = "https://otherexample.com/s2/audio/128k-init-{initId}.mp4" contBaseUrl = resolve(AudioTrack.continuationPattern, T) = "https://otherexample.com/s2/audio/128k-content-{segmentId}.mp4" The final content request URLs are https://otherexample.com/s2/ audio/128k-init-{initId}.mp4 and https://otherexample.com/s2/ audio/128k-content-{segmentId}.mp4 for the Initialization Stream and Continuation Stream respectively. A.2. Initialization Stream In the second step, the client uses the Manifest to retrieve and then parse an Initialization Packet. A.2.1. Retrieving Initialization Packets The client decides to retrieve the only audio Track of the active Presentation. The URL pattern for the Initialization Stream of this Track is https://otherexample.com/s2/audio/128k-init-{initId}.mp4. The client opts to retrieve the most recent Initialization Packet and sends out a request: GET /s2/128k-init-now.mp4 HTTP/1.1 Host: otherexample.com Accept: */* The server responds with the following headers HTTP/1.1 200 OK Content-Type: audio/mp4 Content-Length: 742 Date: Wed, 31 Mar 2021 08:00:02 GMT and a binary body containing the ISOBMFF media data of the audio Initialization Packet. The client repeats this to retrieve one of the video Tracks. Speelmans Expires 14 October 2023 [Page 74] Internet-Draft HESP April 2023 A.2.2. Parsing offset information The client parses the ISOBMFF boxes in the audio Initialization Packet. Once the emsg box with scheme ID urn:theo:hesp:2020 and value initdata is found, its message_data field is parsed. In this case, message_data equals {"index":200,"offset":63275}. The following media data for the chosen audio Track is available in the Continuation Segment with ID 200 and at a byte offset of 63275. A.3. Continuation Stream In the final step, the client uses the retrieved information to retrieve Continuation Segments and reaches playback. A.3.1. Retrieving Continuation Segments The client retrieves the Continuation Segment of the chosen audio Track. The URL pattern for the Continuation Stream of this Track is https://otherexample.com/s2/audio/128k-content-{segmentId}.mp4. The client sends out a request for the segment with ID 200, starting at offset 63275: GET /s2/128k-content-200.mp4 HTTP/1.1 Host: otherexample.com Accept: */* Range: bytes=63275-9007199254740991 As discussed in Section 5.3.2, a sufficiently large end byte value is chosen to ensure the entire range is retrieved. The server responds with the following headers HTTP/1.1 200 OK Content-Type: audio/mp4 Content-Range: bytes 63275-9007199254740991/9007199254677716 Transfer-Encoding: chunked Date: Wed, 31 Mar 2021 08:00:03 GMT and a (chunked) binary body containing the ISOBMFF media data of the Continuation Segment. The client repeats this for the chosen video Track and uses the retrieved media data to reach playback. The Manifest that was retrieved previously contains sufficient information to retrieve new Continuation Segments from this point on. Speelmans Expires 14 October 2023 [Page 75] Internet-Draft HESP April 2023 Appendix B. CDNs A Content Delivery Network (CDN) MAY be employed to increase the scalability and cacheability for delivering HESP. While the HESP protocol uses HTTP/1.1 and delivery should be possible over most HTTP CDNs, care must be taken to ensure that the CDN has all the required features. To correctly handle HESP, the CDN MUST either support HTTP/1.1 with chunked transfer encoding or support HTTP/2. It MUST also support Range Requests as well as the caching of the partial object responses. This ensures that HESP requests and responses pass correctly through the CDN and that responses can be cached for future use. The CDN SHOULD support collapsing multiple HTTP/1.1 Range Requests with overlapping byte-ranges into a single request. This ensures that two requests with byte-ranges that are partially overlapping require only a single request to the media server for the overlapping part. This reduces the number of concurrent requests arriving on the media server. Appendix C. HESP Profiles (using H.264 as video codec) In this annex, we describe two possible profiles for video Tracks of HESP streams. Both profiles place certain requirements on the underlying H.264 encoding of the HESP stream. C.1. Maximal Gain Profile The goal of this profile is to allow the stream to reach the lowest latency and zapping times possible using the HESP protocol. In this profile, it should be ensured that an Initialization Packet exists for each frame of the Continuation Stream. As a result, a client can start playback, seek and switch between Tracks at any time position of the stream. The Initialization Stream for Tracks of the Maximal Gain Profile must satisfy the following requirements: * The frame rate of the Initialization Stream MUST match the Continuation Stream. * Each media sample of the Initialization Stream MUST be independent (i.e., an I frame in H.264) and individually addressable (the latter is currently always true for HESP.) Speelmans Expires 14 October 2023 [Page 76] Internet-Draft HESP April 2023 The Continuation Stream for Tracks of the Maximal Gain Profile must satisfy the following requirements: * Each media sample of the Continuation Stream MUST be either independent (i.e., an I frame in H.264) or dependent on the media sample directly preceding it in decode order (i.e., a P frame referencing only the previous frame.) * Each CMAF Fragment of the Continuation Segment MUST only contain one media sample. * Each Continuation Segment SHOULD be significantly long (values of multiple minutes are possible and encouraged.) +----+----+----+----+----+----+----+----+----+----+ time positions | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | +----+----+----+----+----+----+----+----+----+----+ +----+----+----+----+----+----+----+----+----+----+ initialization | IDR| IDR| IDR| IDR| IDR| IDR| IDR| IDR| IDR| IDR| stream | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | +----+----+----+----+----+----+----+----+----+----+ | REF| REF| REF| REF| REF| REF| REF| REF| REF| REF| | a | b | c | d | e | f | g | h | i | j | +----+----+----+----+----+----+----+----+----+----+ +----+----+----+----+----+----+----+----+----+----+ continuation | I,P| I,P| I,P| I,P| I,P| I,P| I,P| I,P| I,P| I,P| stream | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | +----+----+----+----+----+----+----+----+----+----+ | | | | | \___ position c | | | \___ position b | \___ position a Figure 4: Maximum Gain Profile C.2. Compatibility Profile The goal of this profile is to allow media data from other HTTP-based adaptive bitrate protocols to be reused. This comes at the cost of some optimizations made by the previous profile. In this profile, it is not possible to start playback at any time position of the stream, as it is not possible for Initialization Packets to refer to every sample of a Continuation Segment. The Initialization Stream for Tracks of the Compatibility Profile must satisfy the following requirements: Speelmans Expires 14 October 2023 [Page 77] Internet-Draft HESP April 2023 * Each media sample of the Initialization Stream MUST be independent (i.e., an I frame in H.264) and individually addressable (the latter is currently always true for HESP.) * Initialization Packets MUST contain a reference to the subsequent sample in the Continuation Segment, where this subsequent sample MUST be either independent (i.e., an I frame in H.264) or dependent on the media sample directly preceding it in decode order (i.e., a P frame referencing only the previous frame.) If the subsequent sample does not meet this constraint, then this Initialization Packet MUST NOT be published. Instead, the last valid Initialization Packet MUST be returned if this Sequence Number is queried. The Continuation Stream for Tracks of the Compatibility Profile must satisfy the following requirements: * Continuation Segments SHOULD NOT exceed a duration of 30 seconds. * Each CMAF Fragment of the Continuation Segment MUST contain at most the amount of media samples of a sub-GOP (defined below.) * The following GOP structure must be followed in the underlying H.264 stream: I, B (repeated n times), P, B (repeated n times), P, where n lies between 0 and 4. * Each sub-GOP (B ... B P) MUST depend on at most one previous frame (allowing for keyframe insertion.) C.2.1. Example Figure 5 depicts a part of H.264 output of 7 frames, sorted in decode order. The dependencies of each frame are shown with arrows. ______________________________________ | | | | V | | | +----+ +----+ +----+ +----+ +----+ +----+ +----+ |####| |%%%%| |%%%%| |%%%%| |@@@@| |@@@@| |@@@@| | I1 | | P4 | | B2 | | B3 | | P7 | | B5 | | B6 | +----+ +----+ +----+ +----+ +----+ +----+ +----+ ^ | ^ | | ^ | | |_____| | | | |______| | | | | | | | |________|_____| | |______________| | | |______________________| Figure 5: Continuation stream with sub-GOPs Speelmans Expires 14 October 2023 [Page 78] Internet-Draft HESP April 2023 C.2.1.1. Sub GOPs A "sub-GOP" defines a set of B and P frames that only depend on one previous frame. In Figure 5, there are 3 sub-GOPs: * sub-GOP 1 (####) contains only a single I frame. * sub-GOP 2 (%%%%) contains a P frame (P4) that only depends on I1; all B frames depend on I1 and P4. * sub-GOP 3 (@@@@) contains a P frame (P7) that only depends on P4; all B frames depend on P7 and P4. C.2.1.2. Initialization Packets An Initialization Packet can be published if the subsequent media sample of the Continuation Stream depends on at most one previous frame. For Figure 5, this is the case at the following positions: * position 1: an Initialization Packet can be published. It will contain IDR1 (a keyframe matching the timestamp of I1) and will reference P4, the subsequent media sample of the Continuation Stream that only depends on I1. On the client-side, the media data will be decoded with IDR1 inserted at the location of I1. * position 4: an Initialization Packet can be published. It will contain IDR4 (a keyframe matching the timestamp of P4) and will reference P7, the subsequent media sample of the Continuation Stream that only depends on P4. On the client-side, the media data will be decoded with IDR4 inserted at the location of P4. A client requesting an Initialization Packet at other time positions must receive the most recent valid Initialization Packet. For example, that means that a request for an Initialization Packet at position 2 in Figure 5 must return the Initialization Packet at position 1. Author's Address Pieter-Jan Speelmans (editor) THEO Technologies Leuven Belgium Email: pieter-jan.speelmans@theoplayer.com Speelmans Expires 14 October 2023 [Page 79]