|Internet-Draft||WARP Streaming Format||June 2023|
|Law, et al.||Expires 10 December 2023||[Page]|
- Media Over QUIC
- Intended Status:
WARP Streaming Format
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:firstname.lastname@example.org), which is archived at https://mailarchive.ietf.org/arch/browse/moq/. Subscribe at https://www.ietf.org/mailman/listinfo/moq/.¶
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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. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
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.¶
Each codec bitstream MUST be packaged in to a sequence of Objects within a separate track.¶
The catalog object 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.¶
The format of the CATALOG object payload is as follows:¶
- Media format type: this MUST hold the value 0x001 (see Section 7). This value MUST NOT be encrypted.¶
- Version: this MUST be the version of WARP to which the media packaging and catalog serialization conforms.¶
- Parent object sequence: 0 if this object represents an independent catalog or the [MoQTransport] (Sect 6.2) parent object sequence if this represents a delta update.¶
- Track change count: The number of track changes described by the catalog. A catalog update describing 0 tracks, or deleting all existing tracks, SHALL be interpreted by the WARP client to mean that the publishing session is complete. A WARP client SHOULD process all changes before making a subscription selection.¶
Each track change is described by a track change descriptor with the format:¶
- Full track name length: the length of the full track name field¶
- Full track name: the Full Track Name as defined by [MoQTransport] (Sect 2.3.1). Track names MUST never be reused. If a track is published and then unpublished, it must be allocated a new track name before it is re-published. A catalog MUST NOT reference itself i.e the the track name must not be "catalog".¶
- Operation: a binary flag. 1 if the track is being added and 0 if it is being deleted. A publisher MUST NOT signal deletion of a track that has not been previously added.¶
- Change payload: depends upon the value of the operation flag. If the operation is a 1 (add), then it SHALL hold an Initialization Header. If the operation is 0 (delete), then it SHALL hold a Deletion Header.¶
- Init length: the length of the init payload¶
- Init payload: The init payload MUST consist of a File Type Box (ftyp) followed by a Movie Box (moov). This Movie Box (moov) consists of Movie Header Boxes (mvhd), Track Header Boxes (tkhd), Track Boxes (trak), followed by a final Movie Extends Box (mvex). These boxes MUST NOT contain any samples and MUST have a duration of zero. A Common Media Application Format Header [CMAF] meets all these requirements.¶
Object Delivery Order MUST match the Object sequence number.¶
The media object payload:¶
MUST consist of a Segment Type Box (styp) followed by any number of media fragments. Each media fragment consists of a Movie Fragment Box (moof) followed by a Media Data Box (mdat). The Media Fragment Box (moof) MUST contain a Movie Fragment Header Box (mfhd) and Track Box (trak) with a Track ID (
track_ID) matching a Track Box in the initialization fragment.¶
- MUST contain a single [ISOBMFF] track.¶
- MUST contain media content encoded in decode order. This implies an increasing decoding time stamp (DTS).¶
- MAY contain any number of frames/samples.¶
- MAY have gaps between frames/samples.¶
- MAY overlap with other objects. This means timestamps may be interleaved between objects.¶
Two options are RECOMMENDED for packaging CMAF content into WARP media objects:¶
- the first is to package a complete CMAF Fragment (see [CMAF] sect 6.6.1) into a single object within each group. This results in there being a single GOP (Group of Pictures) in the media object and a single media object per group.¶
- The second is to package a CMAF chunk (see [CMAF] sect 6.6.5), in which the mdat holds a single frame of video, or sample of audio, into each object and to assign a unique group ID to each fragment. This approach is RECOMMENDED to minimize latency.¶
A WARP publisher MUST publish a catalog track object before publishing any media track objects.¶
At the completion of a session, a publisher should publish a catalog object with track count of 0. This SHOULD be interpreted by receivers that the publish session is complete.¶
ToDo - details of how keys are exchanged and license servers signalled.¶
- "International Organization for Standardization - Information technology - MPEG systems technologies - Part 7: Common encryption in ISO base media file format files", .
- "Information technology -- Multimedia application format (MPEG-A) -- Part 19: Common media application format (CMAF) for segmented media", .
- "Information technology -- Coding of audio-visual objects -- Part 12: ISO Base Media File Format", .
- Curley, L., Pugin, K., Nandakumar, S., and V. Vasiliev, "Media over QUIC Transport", Work in Progress, Internet-Draft, draft-lcurley-moq-transport-00, , <https://datatracker.ietf.org/doc/html/draft-lcurley-moq-transport-00>.
- Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/rfc/rfc2119>.
- Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/rfc/rfc8174>.
- Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, , <https://www.rfc-editor.org/rfc/rfc9000>.