Internet Engineering Task Force (IETF) M. Westerlund
Request for Comments: 9751 Ericsson
Updates: 8088 March 2025
Category: Standards Track
ISSN: 2070-1721
Closing the RTP Payload Format Media Types Registry
Abstract
The working group process and the authors of RTP payload formats have
sometimes failed to ensure that the media types are registered in the
IANA "RTP Payload Format Media Types" registry as recommended by RFC
8088. To simplify the process and rely only on the "Media Types"
registry, this document closes the RTP payload- specific registry.
In addition, it updates the instruction in RFC 8088 to reflect this
change.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9751.
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Table of Contents
1. Introduction
2. Update to How to Write an RTP Payload Format
3. IANA Considerations
4. Security Considerations
5. References
5.1. Normative References
5.2. Informative References
Acknowledgments
Author's Address
1. Introduction
Sometimes, authors defining new Real-time Transport Protocol (RTP)
payload formats forgot to specify registration of the format's media
type in the "RTP Payload Format Media Types" registry [RTP-FORMATS]
as recommended by [RFC8088]. In practice, this has no real impact.
This registry is not used for any purpose other than to track which
media types actually have RTP payload formats, which can be done
through other means.
It is required that media types be registered in the "Media Types"
registry [MEDIA-TYPES] to identify the format in various signalling
usages, avoid collisions, and reference the defining specifications.
To resolve this situation, this document:
* updates the "RTP Payload Format Media Types" registry to include
known RTP payload formats at the time of writing,
* closes the "RTP Payload Format Media Types" registry to future
registrations and lists this RFC as a reference, and
* removes from [RFC8088] the instruction to register RTP payload
formats in the "RTP Payload Format Media Types" registry.
The origins of the "RTP Payload Format Media Types" registry, as
referenced in [RTP-FORMATS], are unclear. The registry cites
[RFC4855] as providing the instructions for its maintenance.
However, upon reviewing RFC 4855, no text has been found that defines
the registry's purpose and operational rules. Further attempts to
trace the registry's creation have failed to uncover any references
to its establishment. It is likely that the registry was created
based on email correspondence or at the request of an Area Director.
Consequently, there is no known specification for this registry that
requires updating upon its closure.
2. Update to How to Write an RTP Payload Format
The IANA Considerations section of "How to write an RTP Payload
Format" (Section 7.4 of [RFC8088]) mandates that RTP payload formats
shall be registered in the "RTP Payload Format Media Types" registry.
The following paragraph is updated as shown below, thus removing the
need for media types to be registered in the "RTP Payload Format
Media Types" registry. Note that this update does not impact the
rest of RFC 8088's status as an Informational RFC.
OLD:
| Since all RTP payload formats contain a media type specification,
| they also need an IANA Considerations section. The media type
| name must be registered, and this is done by requesting that IANA
| register that media name. When that registration request is
| written, it shall also be requested that the media type is
| included under the "RTP Payload Format media types" sub-registry
| of the RTP registry (http://www.iana.org/assignments/rtp-
| parameters).
NEW:
| Since all RTP payload formats contain a media type specification,
| they also need an IANA Considerations section. The media type
| name must be registered, and this is done by requesting that IANA
| register that media name in the "Media Types" registry
| (https://www.iana.org/assignments/media-types/).
3. IANA Considerations
IANA has added the following RTP payload types to the "RTP Payload
Format Media Types" registry [RTP-FORMATS].
+=============+==========+===========+==========+==================+
| Media Type | Subtype | Clock | Channels | Reference |
| | | Rate (Hz) | (audio) | |
+=============+==========+===========+==========+==================+
| application | flexfec | | | RFC 8627 |
+-------------+----------+-----------+----------+------------------+
| audio | EVRCNW | 16000 | | RFC 6884 |
+-------------+----------+-----------+----------+------------------+
| audio | EVRCNW0 | 16000 | | RFC 6884 |
+-------------+----------+-----------+----------+------------------+
| audio | EVRCNW1 | 16000 | | RFC 6884 |
+-------------+----------+-----------+----------+------------------+
| audio | aptx | | | RFC 7310 |
+-------------+----------+-----------+----------+------------------+
| audio | opus | 48000 | | RFC 7587 |
+-------------+----------+-----------+----------+------------------+
| audio | G711-0 | | | RFC 7650 |
+-------------+----------+-----------+----------+------------------+
| audio | flexfec | | | RFC 8627 |
+-------------+----------+-----------+----------+------------------+
| text | flexfec | | | RFC 8627 |
+-------------+----------+-----------+----------+------------------+
| text | ttml+xml | | | RFC 8759 |
+-------------+----------+-----------+----------+------------------+
| video | VP8 | 90000 | | RFC 7741 |
+-------------+----------+-----------+----------+------------------+
| video | AV1 | 90000 | | [AV1-Media-Type] |
+-------------+----------+-----------+----------+------------------+
| video | HEVC | 90000 | | RFC 7798 |
+-------------+----------+-----------+----------+------------------+
| video | smpte291 | | | RFC 8331 |
+-------------+----------+-----------+----------+------------------+
| video | VVC | 90000 | | RFC 9328 |
+-------------+----------+-----------+----------+------------------+
| video | EVC | 90000 | | RFC 9584 |
+-------------+----------+-----------+----------+------------------+
| video | flexfec | | | RFC 8627 |
+-------------+----------+-----------+----------+------------------+
Table 1: Payload Types Added to the RTP Payload Format Media
Types Registry
IANA has updated the following entries in the "RTP Payload Format
Media Types" registry [RTP-FORMATS].
+============+===========+=================+==========+===========+
| Media Type | Subtype | Clock Rate (Hz) | Channels | Reference |
| | | | (audio) | |
+============+===========+=================+==========+===========+
| audio | MP4A-LATM | | | RFC 6416 |
+------------+-----------+-----------------+----------+-----------+
| video | MP4V-ES | 90000 | | RFC 6416 |
+------------+-----------+-----------------+----------+-----------+
Table 2: Payload Types Updated in RTP Payload Format Media
Types Registry
IANA has also closed the "RTP Payload Format Media Types" registry
[RTP-FORMATS] to any further registrations. IANA added the following
to the registry note:
NEW:
| This registry has been closed; it was considered redundant because
| all RTP payload formats are part of the [Media Types registry]
| (https://www.iana.org/assignments/media-types). See RFC 9751 for
| further details.
In addition, IANA updated the note in the "RTP Payload Format Media
Types" registry [RTP-FORMATS] as follows:
OLD:
| Registration procedures and a registration template can be found
| in [RFC4855].
NEW:
| It was previously stated that registration procedures and a
| registration template can be found in [RFC4855]. As documented in
| RFC 9751, this is not the case.
4. Security Considerations
This document has no security considerations as it defines an
administrative rule change.
5. References
5.1. Normative References
[AV1-Media-Type]
IANA, "video/AV1",
<https://www.iana.org/assignments/media-types/video/AV1>.
[MEDIA-TYPES]
IANA, "Media Types",
<https://www.iana.org/assignments/media-types>.
[RFC8088] Westerlund, M., "How to Write an RTP Payload Format",
RFC 8088, DOI 10.17487/RFC8088, May 2017,
<https://www.rfc-editor.org/info/rfc8088>.
[RTP-FORMATS]
IANA, "RTP Payload Format Media Types",
<https://www.iana.org/assignments/rtp-parameters>.
5.2. Informative References
[RFC4855] Casner, S., "Media Type Registration of RTP Payload
Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
<https://www.rfc-editor.org/info/rfc4855>.
Acknowledgments
The author thanks Jonathan Lennox, Zaheduzzaman Sarker, Bernard
Aboba, Elwyn Davies, Wes Hardaker, Gunter Van de Velde, Éric Vyncke,
Mahesh Jethanandani, and Hyunsik Yang for their reviews and editorial
fixes.
Author's Address
Magnus Westerlund
Ericsson
Email: magnus.westerlund@ericsson.com