WARP Streaming Format
draft-law-moq-warpstreamingformat-00

Media Over QUIC                                                   W. Law
Internet-Draft                                                    Akamai
Intended status: Informational                                 L. Curley
Expires: 10 December 2023                                         Twitch
                                                             V. Vasiliev
                                                                  Google
                                                           S. Nandakumar
                                                                   Cisco
                                                                K. Pugin
                                                                    Meta
                                                             8 June 2023

                         WARP Streaming Format
                  draft-law-moq-warpstreamingformat-00

Abstract

   This document specifies the WARP Streaming Format, designed to
   operate on Media Over QUIC Transport.

About This Document

   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.

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/.

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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on 10 December 2023.

Copyright Notice

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   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Packaging . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Catalog objects . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Media Objects . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Workflow  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Content protection and encryption . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   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.

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   This document describes version 1 of the streaming format.

2.  Conventions and Definitions

   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.

3.  Packaging

   Each codec bitstream MUST be packaged in to a sequence of Objects
   within a separate track.

   Media tracks SHOULD be media-time aligned.  CMAF [CMAF] Aligned
   Switching Sets meet this requirement.  A receiver SHOULD be able to
   cleanly switch between media tracks at group boundaries.

   Each group MUST be independently decodeable.  Assigning a new group
   ID to each CMAF Fragment (see [CMAF] Sect 6.6.1) meets this
   requirement.

3.1.  Catalog objects

   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:

   CATALOG payload {
     media format type (i),
     version (i),
     parent object sequence (i),
     track change count (i),
     track change descriptors (..)
   }

                        Figure 1: WARP CATALOG body

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   *  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:

   Track Change Descriptor {
     full track name length (i),
     full track name (..),
     operation (1),
     change payload(..)
   }

                     Figure 2: Track change descriptor

   *  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.

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   Initialization Header {
     init length (i)
     init payload (..)
   }

                      Figure 3: Initialization 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.

   Deletion Header {
     Last group: (i),
     Last object: (i)
   }

                         Figure 4: Deletion Header

   *  Last group: holds the last [MoQTransport] Group sequence number
      published under that track name.

   *  Last object: holds the last [MoQTransport] Object sequence number
      published under that track name.

3.2.  Media Objects

   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).

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   *  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.

4.  Workflow

   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.

5.  Content protection and encryption

   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
   signalled.

6.  Security Considerations

   ToDo

7.  IANA Considerations

   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.

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8.  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]     "Information technology -- Multimedia application format
              (MPEG-A) -- Part 19: Common media application format
              (CMAF) for segmented media", March 2020.

   [ISOBMFF]  "Information technology -- Coding of audio-visual objects
              -- Part 12: ISO Base Media File Format", December 2015.

   [MoQTransport]
              Curley, L., Pugin, K., Nandakumar, S., and V. Vasiliev,
              "Media over QUIC Transport", Work in Progress, Internet-
              Draft, draft-lcurley-moq-transport-00, 26 May 2023,
              <https://datatracker.ietf.org/doc/html/draft-lcurley-moq-
              transport-00>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/rfc/rfc9000>.

Acknowledgments

   *  Alan Frindell

   *  Ali Begen

   *  Charles Krasic

   *  Christian Huitema

   *  Cullen Jennings

   *  Hang Shi

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   *  James Hurley

   *  Jordi Cenzano

   *  Mike English

   *  the MoQ Workgroup and mailing lists.

Authors' Addresses

   Will Law
   Akamai
   Email: wilaw@akamai.com

   Luke Curley
   Twitch
   Email: kixelated@gmail.com

   Victor Vasiliev
   Google
   Email: vasilvv@google.com

   Suhas Nandakumar
   Cisco
   Email: snandaku@cisco.com

   Kirill Pugin
   Meta
   Email: ikir@meta.com

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