



moq                                                            L. Curley
Internet-Draft                                              22 July 2025
Intended status: Informational                                          
Expires: 23 January 2026


                         Media over QUIC - Hang
                       draft-lcurley-moq-hang-00

Abstract

   Hang is a real-time conferencing protocol built on top of moq-lite.
   A room consists of multiple participants who publish media tracks.
   All updates are live, such as a change in participants or media
   tracks.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the Media Over QUIC
   Working Group mailing list (moq@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/moq/.

   Source for this draft and an issue tracker can be found at
   https://github.com/kixelated/moq-drafts.

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
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   This Internet-Draft will expire on 23 January 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Conventions and Definitions . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Discovery . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Catalog . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Root  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Video . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.3.  Audio . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Media . . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  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.

2.  Terminology

   Hang is built on top of moq-lite [moql] and uses much of the same
   terminology.  A quick recap:

   *  *Broadcast*: A collection of Tracks from a single publisher.

   *  *Track*: An series of Groups, each of which can be delivered and
      decoded _out-of-order_.

   *  *Group*: An series of Frames, each of which must be delivered and
      decoded _in-order_.

   *  *Frame*: A sized payload of bytes representing a single moment in
      time.



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   Hang introduces additional terminology:

   *  *Room*: A collection of participants, publishing under a common
      prefix.

   *  *Participant*: A moq-lite broadcaster that may produce any number
      of media tracks.

   *  *Catalog*: A JSON document that describes each available media
      track, supporting live updates.

   *  *Container*: A tiny header in front of each media payload
      containing the timestamp.

3.  Discovery

   The first requirement for a real-time conferencing application is to
   discover other participants in the same room.  Hang does this using
   moq-lite's ANNOUNCE capabilities.

   A room consists of a path.  Any participants within the room MUST
   publish a broadcast with the room path as a prefix and it SHOULD end
   with the .hang suffix.

   For example:

   /room/alice.hang
   /room/bob.hang
   /other/zoe.hang

   A participant issues an ANNOUNCE_PLEASE message to discover any other
   participants in the same room.  The server (relay) will then respond
   with an ANNOUNCE message for any matching broadcasts, including their
   own.

   For example:

   ANNOUNCE_PLEASE prefix=/room/
   ANNOUNCE suffix=alice.hang active=true
   ANNOUNCE suffix=bob.hang   active=true

   If a publisher no longer wants to participant, or is disconnected
   somehow, their presence will be unannounced.  Publishers and
   subscribers SHOULD terminate any subscriptions once a participant is
   unannounced.

   ANNOUNCE suffix=alice.hang active=false




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4.  Catalog

   The catalog describes the available media tracks for a single
   participant.  It's a JSON document that extends the the W3C WebCodecs
   specification.

   The catalog is published as a catalog.json track within the broadcast
   so it can be updated live as the participant's media tracks change.
   A participant MAY forgo publishing a catalog if it does not wish to
   publish any media tracks now and in the future.

   The catalog track consists of multiple groups, one for each update.
   Each group contains a single frame with UTF-8 JSON.  A publisher MUST
   NOT write multiple frames to a group until a future specification
   includes a delta-encoding mechanism.

4.1.  Root

   The root of the catalog is a JSON document with the following schema:

   type Catalog = {
           "audio": AudioTrack[],
           "video": VideoTrack[],
   }

   When there are multiple audio or video tracks, they SHOULD describe
   the same content.  For example, different resolutions, codecs,
   bitrates, etc.  If a participant wants to publish unrelated content,
   for example sharing the screen in addition to a webcam, it SHOULD
   publish a separate broadcast (and catalog).

   Additional fields MAY be added based on the application.  The catalog
   SHOULD be mostly static, delegating any dynamic content to other
   tracks.  Additionally, a catalog SHOULD describe optional content,
   allowing the client to decide if it wants to subscribe.

   For example, a "chat" field should include the name of a chat track,
   not individual chat messages.  This way catalog updates are rare and
   a client MAY choose to not subscribe.

4.2.  Video

   A video track contains the necessary information to decode a video
   stream.

   Hang uses the VideoDecoderConfig (https://www.w3.org/TR/
   webcodecs/#video-decoder-config).  Any Uint8Array fields are hex-
   encoded into a string.



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   The track field includes the name and priority of the track within
   the broadcast.

   type VideoTrack = {
           "track": {
                   "name": string,
                   "priority": number,
           },
           "config": VideoDecoderConfig,
   }

   For example:

   {
           "track": {
                   "name": "video",
                   "priority": 2
           },
           "config": {
                   "codec": "avc1.64001f",
                   "codedWidth": 1280,
                   "codedHeight": 720,
                   "bitrate": 6000000,
                   "framerate": 30.0
           }
   }

4.3.  Audio

   An audio track contains the necessary information to decode an audio
   stream.

   The track field includes the name and priority of the track within
   the broadcast.

   The config field contains an AudioDecoderConfig
   (https://www.w3.org/TR/webcodecs/#audio-decoder-config).  Any
   Uint8Array fields are hex-encoded into a string.

   type AudioTrack = {
           "track": {
                   "name": string,
                   "priority": number,
           },
           "config": AudioDecoderConfig,
   }

   For example:



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   {
           "track": {
                   "name": "audio",
                   "priority": 1
           },
           "config": {
                   "codec": "opus",
                   "sampleRate": 48000,
                   "numberOfChannels": 2,
                   "bitrate": 128000
           }
   }

5.  Media

   Media tracks are split into groups and further into frames.

   A group consists of one or more frames in decode order.  Each group
   MUST start with a keyframe.  If a codec supports delta frames
   (video), then all subsequent frames MUST be delta frames.  Otherwise,
   a group MAY consist of multiple keyframes (audio).

   Each "frame" consists of a tiny "container" containing the timestamp
   and codec specific payload.  The timestamp is the presentation
   timestamp in microseconds encoded as a QUIC variable-length integer
   (62-bit max).  The remainder of the frame payload is codec specific.

6.  Security Considerations

   TODO Security

7.  IANA Considerations

   This document has no IANA actions.

8.  Normative References

   [moql]     "*** BROKEN REFERENCE ***".

   [moqt]     Nandakumar, S., Vasiliev, V., Swett, I., and A. Frindell,
              "Media over QUIC Transport", Work in Progress, Internet-
              Draft, draft-ietf-moq-transport-13, 7 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-moq-
              transport-13>.







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   [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>.

Acknowledgments

   TODO acknowledge.

Author's Address

   Luke Curley
   Email: kixelated@gmail.com


































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