| Internet-Draft | WARP Streaming Format | January 2024 |
| Law, et al. | Expires 25 July 2024 | [Page] |
This document specifies the WARP Streaming Format, designed to operate on Media Over QUIC Transport.¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://wilaw.github.io/MoQ/draft-law-moq-warpmedia.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-law-moq-warpstreamingformat/.¶
Discussion of this document takes place on the Media Over QUIC Working Group mailing list (mailto:moq@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/moq/. Subscribe at https://www.ietf.org/mailman/listinfo/moq/.¶
Source for this draft and an issue tracker can be found at https://github.com/wilaw/MoQ.¶
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WARP Streaming Format (WARP) is a media format designed to deliver CMAF [CMAF] compliant media content over Media Over QUIC Transport (MOQT) [MoQTransport]. WARP works by fragmenting the bitstream into objects that can be independently transmitted. WARP leverages a simple prioritization strategy of assigning newer content a higher delivery order, allowing intermediaries to drop older data, and video over audio, in the face of congestion. Either complete Groups of Pictures (GOPS) [ISOBMFF] or individual frames are mapped to MoQTransport Objects. WARP is targeted at interactive levels of live latency.¶
This document describes version 1 of the streaming format.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
This document uses the conventions detailed in Section 1.3 of [RFC9000] when describing the binary encoding.¶
WARP delivers CMAF-packaged media bitstreams. This specification references [CMAFpackaging] to define how CMAF packaged bitstreams are mapped to [MoQTransport] groups and objects.¶
Both CMAF Object mappings [CMAFpackaging] Section 4 are supported and a content producer may use either. To identify to consumers which object mapping mode is being used for a given Track, a new track field is defined as per table 1.¶
| Field | Name | Required | Location | JSON type | Definition |
|---|---|---|---|---|---|
| WARP packaging mode | warp-packaging | yes | RT | String | See Section 3.1 |
The packaging mode value is defined by Table 2.¶
| warp-packing field value | Condition | Explanation |
|---|---|---|
| frag-per-group | [CMAFpackaging] 4.1 is active | Each CMAF Fragment is placed in a single MOQT Object and there is one MOQT Object per MOQT Group |
| chunk-per-object | [CMAFpackaging] 4.2 is active | Each CMAF chunk is placed in a MOQT Object and there is one MOQT Group per CMAF Fragment |
WARP Tracks MAY be time-aligned. Those that are, are subject to the following requirements:¶
Time-aligned tracks MUST be advertised in the catalog as belonging to a common render group.¶
The presentation time of the first media sample contained within the first MOQT Object of each equally numbered MOQT Group MUST be identical.¶
A consequence of this restriction is that a WARP receiver SHOULD be able to cleanly switch between time-aligned media tracks at group boundaries.¶
The catalog and media object payloads MAY be encrypted. Common Encryption [CENC] with 'cbcs' mode (AES CBC with pattern encryption) is the RECOMMENDED encryption method.¶
ToDo - details of how keys are exchanged and license servers signaled. May be best to extend catalog spec to allow the specification of content protection schema, along with any pssh or protection initialization data.¶
WARP uses the Common Catalog Format {[COMMON-CATALOG-FORMAT}} to describe the content being produced by a publisher.¶
Per Sect 5.1 of [COMMON-CATALOG-FORMAT], WARP registers an entry in the "MoQ Streaming Format Type" table. The type value is 0x001, the name is "WARP Streaming Format" and the RFC is XXX.¶
Every WARP catalog MUST declare a streaming format type (See Sect 3.2.1 of [COMMON-CATALOG-FORMAT]) value of 1.¶
Every WARP catalog MUST declare a streaming format version (See Sect 3.2.1 of [COMMON-CATALOG-FORMAT]) corresponding to the version of this document.¶
The catalog track MUST have a track name of "catalog". A catalog object MAY be independent of other catalog objects or it MAY represent a delta update of a prior catalog object. The first catalog object published within a new group MUST be independent. A catalog object SHOULD only be published only when the availability of tracks changes.¶
Each catalog update MUST be mapped to a discreet moq-transport object.¶
The MOQT Groups and MOQT Objects need to be mapped to moq-transport Streams. Irrespective of the Section 3.1 in place, each MOQT Object MUST be mapped to a new moq-transport Stream.¶
A WARP publisher MUST publish a catalog track object before publishing any media track objects.¶
At the completion of a session, a publisher MUST publish a catalog update that removes all currently active tracks. This action SHOULD be interpreted by receivers to mean that the publish session is complete.¶
This document creates a new entry in the "MoQ Streaming Format" Registry (see [MoQTransport] Sect 8). The type value is 0x001, the name is "WARP Streaming Format" and the RFC is XXX.¶