MoQ Media Interop

Status of This Memo

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Table of Contents

1. Introduction

This protocol specifies a simple mechanism for sending media (video and audio) over MOQT for both live-streaming and VC use cases. The protocol is flexible in order to support this range of use cases.¶

Media parameters can be updated in the middle of a the track (ex: frame rate, resolution, codec, etc)¶

The protocol defines a low overhead packaging format optimized for WebCodecs called WCP that is extensible to other formats such as FMP4. This is not LoC [LOC], but will eventually be merged with that specification.¶

2. Protocol Operation

PTS = 11, timebase = 30

PTS(s) = 11/30 = 0.366666

{
  Media Type (i)
  Media payload (..)
}

3. Video H264 in AVCC with WCP Payload Format

{
  Seq ID (i)
  PTS Timestamp (i)
  DTS Timestamp (i)
  Timebase (i)
  Duration (i)
  Wall Clock (i)
  Metadata Size (i)
  Metadata (..)
  Payload (..)
}

• Seq ID: Monotonically increasing counter for this media track.¶

• PTS Timestamp: Presentation timestamp in timebase.¶

TODO: Varint does NOT accept easily negative values, so it could be challenging to encode at start (priming).¶

• DTS Timestamp: Display timestamp in timebase. If B frames are not used, the encoder SHOULD set this to the same value as PTS.¶

TODO: Varint does NOT accept easily negative values, so it could be challenging to encode at start (priming).¶

• Timebase: Denominator used to calculate PTS, DTS, and Duration.¶

• Duration: Duration of Payload in timebase. It will be 0 if not set.¶

• Wall Clock: Epoch time in ms when this frame started being captured. It will be 0 if not set.¶

• Metadata Size: Size in bytes of the metadata section. It will be 0 when no metadata is present.¶

• Metadata: Extra data needed to decode this stream. This will be AVCDecoderConfigurationRecord as described in [ISO14496] section 5.3.3.1, with field lengthSizeMinusOne = 3 (So length = 4). If any other size length is indicated (in AVCDecoderConfigurationRecord), the receiver SHOULD close the session with a Protocol Violation error. Any change in encoding parameters MUST send a new AVCDecoderConfigurationRecord¶

• Payload: H264 with bitstream AVC1 format as described in [ISO14496] section 5.3. Using 4 bytes size field length.¶

4. Audio Opus bitstream Payload Format

{
  Seq ID (i)
  PTS Timestamp (i)
  Timebase (i)
  Sample Freq (i)
  Num Channels (i)
  Duration (i)
  Wall Clock (i)
  Payload (..)
}

• Seq Id: Monotonically increasing counter for this media track.¶

• PTS Timestamp: Indicates PTS in timebase.¶

TODO: Varint does NOT accept easily negative, so it could be challenging to encode at start (priming).¶

• Timebase: Denominator used to calculate PTS and Duration.¶

• Sample Freq: Sample frequency used in the original signal (before encoding).¶

• Num Channels: Number of channels in the original signal (before encoding).¶

• Duration: Duration of Payload in timebase. It will be 0 if not set.¶

• Wall Clock: Epoch time in ms when this frame started being captured. It will be 0 if not set.¶

• Payload: Opus packets, as described in [RFC6716] - section 3¶

5. 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.¶

6. Security Considerations

TODO Security¶

7. IANA Considerations

This document has no IANA actions.¶

8. References

Acknowledgments

TODO acknowledge.¶

Authors' Addresses