Internet DRAFT - draft-mzanaty-moq-loc
draft-mzanaty-moq-loc
Network Working Group M. Zanaty
Internet-Draft S. Nandakumar
Intended status: Informational Cisco
Expires: 14 September 2023 P. Thatcher
Microsoft
13 March 2023
Low Overhead Media Container
draft-mzanaty-moq-loc-00
Abstract
This specification describes a media container format for encoded and
encrypted audio and video media data to be used for interactive media
usecases, with the goal of it being a low overhead format.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 14 September 2023.
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Table of Contents
1. Introduction
1.1. Requirements Notation and Conventions
1.2. Terminology
2. Payload Format
3. Payload Header Data
3.1. Common Header Data
3.2. Video Header Data
3.3. Audio Header Data
4. Header Data Registration
5. Payload Encryption
6. Container Serialization
7. MOQ Transport Mapping
8. Security Considerations
9. IANA Considerations
10. Normative References
Appendix A. Acknowledgements
Authors' Addresses
1. Introduction
This specification describes a low-overhead media container format
for encoded and encrypted audio and video media data. "Low-overhead"
refers to minimal extra encapsulation as well as minimal application
overhead when interfacing with WebCodecs.
The container format description is specified for all audio and video
codecs defined in the WebCodecs Codec Registry. The audio and video
payload bitstream is identical to the internal data inside an
EncodedAudioChunk and EncodedVideoChunk, respectively, specified in
the registry.
In addition to the media payloads, critical metadata is also
specified for audio and video payloads.
A primary motivation is to align with media formats used in WebCodecs
to minimize application overhead when interfacing with WebCodecs.
Other container formats like CMAF or RTP would require more extensive
application overhead in format conversions, as well as larger
encapsultion overhead which may burden some use cases like low
bitrate audio scenarios.
1.1. Requirements Notation and Conventions
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
[RFC2119].
1.2. Terminology
TODO
2. Payload Format
The WebCodecs Codec Registry defines the contents of an
EncodedAudioChunk and EncodedVideoChunk for the audio and video codec
formats in the registry. The "internal data" in these chunks is used
directly in this specification as the payload bitstream.
3. Payload Header Data
This section specified metadata that needs to be carried out as
payload metadata. Payload header data provides necessary information
for intermediaries to perform switching decisions when the payload is
inaccessible, due to encryption.
Section ((#reg)) provides framework for registering new payload
header fields that aren't defined by this specification
3.1. Common Header Data
Following metadata MUST be captured for each media frame
Sequence Number: Identifies a sequentially increasing variable length
integer that is incremented per encoded media frame.
Capture Timestamp in Microseconds: Captures the wall-clock time of
the encoded media frame.
3.2. Video Header Data
Flags for frames which are independent, discardable, or base layer
sync points, as well as temporal and spatial layer identification.
[I-D.ietf-avtext-framemarking] .
3.3. Audio Header Data
Audio Level: captures the magnitude of the audio level of the
corresponding audio frame and values in encoded in 7 bits as defined
in the section 3 of [RFC6464]
4. Header Data Registration
This section details the procedures to register header data fields
that might be useful for a particular class of media applications.
Registering a given metadata field requires the following attributes
to be specified.
Shortname: Short name for the metadata. (Not sent on the wire.)
Description: Detailed description for the metadata. (Not sent on the
wire.)
ID: Identifier assigned by the registry. (varint)
Length: Length of metadata value in bytes. (varint)
Value: Value of metadata. (length bytes)
Registration of type "Specification Required" is followed for
registering new for header data values.
5. Payload Encryption
When end to end encryption is supported, the encoded payload is
encrypted with keys from symmetric keying mechanisms, such a MLS, and
the payload itself is protected using SFrame or equivalent.
6. Container Serialization
The wire encoding of the payload conforming to this specification is
a set of length delimited values as shown below.
The Bytes is obtained as output of AEAD operation for encrypting the
Payload with the header data as additional data input.
+--------+------------+-------+------------+
| Payload | Bytes | Payload | Bytes |
| Len | (0) | Len (1) | (1) | ...
+--------+------------+-------+------------+
7. MOQ Transport Mapping
TODO
8. Security Considerations
TODO
9. IANA Considerations
TODO on specification required for metadata registration.
10. Normative References
[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/info/rfc2119>.
[I-D.ietf-avtext-framemarking]
Zanaty, M., Berger, E., and S. Nandakumar, "Frame Marking
RTP Header Extension", Work in Progress, Internet-Draft,
draft-ietf-avtext-framemarking-13, 11 November 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-avtext-
framemarking-13>.
[RFC6464] Lennox, J., Ed., Ivov, E., and E. Marocco, "A Real-time
Transport Protocol (RTP) Header Extension for Client-to-
Mixer Audio Level Indication", RFC 6464,
DOI 10.17487/RFC6464, December 2011,
<https://www.rfc-editor.org/info/rfc6464>.
Appendix A. Acknowledgements
Thanks to Cullen Jennings for suggestions and review.
Authors' Addresses
Mo Zanaty
Cisco
Email: mzanaty@cisco.com
Suhas Nandakumar
Cisco
Email: snandaku@cisco.com
Peter Thatcher
Microsoft
Email: pthatcher@microsoft.com
