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draft-ietf-avtcore-hevc-webrtc-00.txt
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AVTCORE Working Group B. Aboba
INTERNET-DRAFT P. Hancke
Category: Standards Track Microsoft Corporation
Expires: April 09, 2024 9 October 2023
H.265 Profile for WebRTC
draft-ietf-avtcore-hevc-webrtc-00.txt
Abstract
RFC 7742 defines WebRTC video processing and codec requirements,
including guidance for endpoints supporting the VP8 and H.264 codecs,
which are mandatory to implement. With support for H.265 under
development in WebRTC browsers, similar guidance is needed for
browsers considering support for the H.265 codec, whose RTP payload
format is defined in RFC 7798.
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 http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 09, 2024.
Aboba & Hancke Standards Track [Page 1]
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Copyright Notice
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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. H.265 Support . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . 5
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
"RTP Payload Format for High Efficiency Video Coding (HEVC)"
[RFC7798] defines the encapsulation of H.265 [H.265] within the Real-
time Transport Protocol (RTP) [RFC3550]. While "WebRTC Video
Processing and Codec Requirements" [RFC7742] provides guidance for
endpoints supporting the mandatory to implement VP8 and H.264 codecs,
it does not cover H.265. With H.265 support under development within
browsers [HEVC-WebKit][HEVC-Chrome] there is a need to for an
interoperability profile of [RFC7798] for WebRTC implementations
choosing to support H.265.
1.1. Terminology
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. H.265 Support
Support for the H.265 video codec is OPTIONAL for WebRTC browsers and
non-browsers. Implementations supporting H.265 that conform to this
specification MUST support receiving H.265 and MAY support sending
H.265.
For the H.265 [H.265] codec, endpoints MUST support the payload
formats defined in [RFC7798]. In addition, they MUST support Main
Profile Level 3.1 (level-id=93) and SHOULD support Main Profile Level
4 (level-id=120).
[RFC7798] Section 4.5 defines how Temporal Scalability Control
Information (TSCI) is communicated using PACI Extensions defined in
[RFC7798] Section 4.4.4.2. A WebRTC implementation that has
negotiated use of RTP header extensions containing TSCI information
(such as the Dependency Descriptor [DD]) SHOULD NOT send TSCI
information within the PACI. If TSCI information is being received
in an RTP header extension, implementations MUST ignore TSCI
information contained in the PACI.
Implementations of the H.265 codec have utilized a wide variety of
optional parameters. To improve interoperability, the following
parameter settings are specified:
level-id: Implementations SHOULD include this parameter within SDP
and MUST interpret it when receiving it. If no level-id is present, a
value of 93 (i.e., level 3.1) MUST be inferred.
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tx-mode: Implementations SHOULD NOT include this parameter within
SDP. If no tx-mode parameter is present, a value of "SRST" MUST be
inferred. Implementations MUST support "SRST"; support for "MRST"
and "MRMT" is OPTIONAL. Implementations that do not support "MRST" or
"MRMT" MUST NOT include these tx-mode values in SDP.
sprop-sps, sprop-pps, sprop-vps, sprop-sei: H.265 allows sequence and
picture information to be sent both in-band and out-of-band. WebRTC
implementations MUST signal this information in-band. This means
that WebRTC implementations MUST NOT include these parameters in the
SDP they generate, and SHOULD silently ignore these parameters if
they are received. An IDR sent MUST always be preceded by the
relevant parameter sets sent in a packet (not necessarily a separate
packet) with the same RTP timestamp as the IDR.
When the use of the video orientation (CVO) RTP header extension is
not signaled as part of the SDP, H.265 implementations MAY send and
SHOULD support proper interpretation of Display Orientation SEI
messages.
[RFC7798] Section 8.3 specifies the use of the Reference Picture
Selection Indication (RPSI) in H.265. Implementations MUST use the
RPSI feedback message only as a reference picture selection request,
and MUST NOT use it as positive acknowledgement. Receivers that
detect that H.265 encoder-decoder synchronization has been lost
SHOULD generate an RPSI feedback message if support for RPSI has been
negotiated, unless the receiver has knowledge that the sender does
not support RPSI. Such knowledge can be established during capability
exchange or through previously sent RPSI requests that were not
replied to by the sender through the use of a non-IRAP picture. An
RTP packet-stream sender that receives an RPSI message MUST act on
that message, and SHOULD change the reference picture.
Unless otherwise signaled, WebRTC implementations that support H.265
MUST encode and decode pixels with an implied 1:1 (square) aspect
ratio.
3. Security Considerations
This document is subject to the security considerations described in
Section 7 of [RFC7742].
In addition to those security considerations, H.265 implementers are
advised to take note of the "Security Considerations" Section 9 of
[RFC7798], including requirements pertaining to SEI messages.
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4. IANA Considerations
This document does not require actions by IANA.
5. References
5.1. Normative References
[DD] Alliance for Open Media (AoMedia), "Dependency Descriptor
RTP Header Extension",
https://aomediacodec.github.io/av1-rtp-spec/#dependency-
descriptor-rtp-header-extension, retrieved September 19,
2023.
[H.265] ITU-T, "High efficiency video coding", ITU-T
Recommendation H.265, April 2013.
[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>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <https://www.rfc-editor.org/info/rfc3550>.
[RFC7742] Roach, A. B., "WebRTC Video Processing and Codec
Requirements", RFC 7742, DOI 10.17487/RFC7742, March
2016, <https://www.rfc-editor.org/info/rfc7742>.
[RFC7798] Wang, Y.K., Sanchez, Y., Schierl, T., Wenger, S. and M.
M. Hannuksela, "RTP Payload Format for High Efficiency
Video Coding (HEVC)", RFC 7798, DOI 10.17487/RFC7798,
March 2016, <https://www.rfc-editor.org/info/rfc7798>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", RFC 8174, DOI 10.17487/RFC8174, May
2017, <https://www.rfc-editor.org/info/rfc8174>.
5.2. Informative References
[HEVC-WebKit] Shin, S. Qiu, J. and J. Zhu, "WebRTC HEVC RFC 7798 RTP
Payload Format Implementation",
https://github.com/WebKit/WebKit/pull/15494 (work in
progress), retrieved July 9, 2023.
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[HEVC-Chrome] "Issue 13485: Need the support of H.265",
https://bugs.chromium.org/p/webrtc/issues/detail?
id=13485 (work in progress), submitted December 8, 2021.
Acknowledgments
We would like to thank Stephan Wenger, Jonathan Lennox, Harald
Alvestrand, Jianlin Qiu and Philip Eliasson for their discussions of
this problem space.
Authors' Addresses
Bernard Aboba
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
United States of America
Email: [email protected]
Philipp Hancke
Microsoft Corporation
Talinn, Estonia
Email: [email protected]
Aboba & Hancke Standards Track [Page 6]