rfc9627v1.txt		rfc9627.txt
	Internet Engineering Task Force (IETF) J. Lennox		Internet Engineering Task Force (IETF) J. Lennox
	Request for Comments: 9627 D. Hong		Request for Comments: 9627 8x8 / Jitsi
	Category: Standards Track Vidyo		Category: Standards Track D. Hong
	ISSN: 2070-1721 J. Uberti		ISSN: 2070-1721 Vidyo
			J. Uberti
	S. Holmer		S. Holmer
	M. Flodman		M. Flodman
	Google		Google
	August 2024		February 2025
	The Layer Refresh Request (LRR) RTCP Feedback Message		The Layer Refresh Request (LRR) RTCP Feedback Message
	Abstract		Abstract
	This memo describes the RTCP Payload-Specific Feedback Message Layer		This memo describes the RTCP Payload-Specific Feedback Message Layer
	Refresh Request (LRR), which can be used to request a state refresh		Refresh Request (LRR), which can be used to request a state refresh
	of one or more substreams of a layered media stream. It also defines		of one or more substreams of a layered media stream. This document
	its use with several RTP payloads for scalable media formats.		also defines its use with several RTP payloads for scalable media
			formats.
	Status of This Memo		Status of This Memo
	This is an Internet Standards Track document.		This is an Internet Standards Track document.
	This document is a product of the Internet Engineering Task Force		This document is a product of the Internet Engineering Task Force
	(IETF). It represents the consensus of the IETF community. It has		(IETF). It represents the consensus of the IETF community. It has
	received public review and has been approved for publication by the		received public review and has been approved for publication by the
	Internet Engineering Steering Group (IESG). Further information on		Internet Engineering Steering Group (IESG). Further information on
	Internet Standards is available in Section 2 of RFC 7841.		Internet Standards is available in Section 2 of RFC 7841.
	Information about the current status of this document, any errata,		Information about the current status of this document, any errata,
	and how to provide feedback on it may be obtained at		and how to provide feedback on it may be obtained at
	https://www.rfc-editor.org/info/rfc9627.		https://www.rfc-editor.org/info/rfc9627.
	Copyright Notice		Copyright Notice
	Copyright (c) 2024 IETF Trust and the persons identified as the		Copyright (c) 2025 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Revised BSD License text as described in Section 4.e of the		include Revised BSD License text as described in Section 4.e of the
	Trust Legal Provisions and are provided without warranty as described		Trust Legal Provisions and are provided without warranty as described
	skipping to change at line 73 ¶		skipping to change at line 75 ¶
	7. Security Considerations		7. Security Considerations
	8. IANA Considerations		8. IANA Considerations
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	9.2. Informative References		9.2. Informative References
	Authors' Addresses		Authors' Addresses
	1. Introduction		1. Introduction
	This memo describes an RTCP [RFC3550] Payload-Specific Feedback		This memo describes an RTCP [RFC3550] Payload-Specific Feedback
	Message [RFC4585] Layer Refresh Request (LRR). It is designed to		Message [RFC4585] "Layer Refresh Request" (LRR), which is designed to
	allow a receiver of a layered media stream to request that one or		allow a receiver of a layered media stream to request that one or
	more of its substreams be refreshed such that it can then be decoded		more of its substreams be refreshed. The stream can then be decoded
	by an endpoint that previously was not receiving those layers,		by an endpoint that previously was not receiving those layers,
	without requiring that the entire stream be refreshed (as it would be		without requiring that the entire stream be refreshed (as it would be
	if the receiver sent a Full Intra Request (FIR) [RFC5104]; see also		if the receiver sent a Full Intra Request (FIR) [RFC5104]; see also
	[RFC8082]).		[RFC8082]).
	The feedback message is applicable to both temporally and spatially		The feedback message is applicable to both temporally and spatially
	scaled streams and to both single-stream and multi-stream scalability		scaled streams and to both single-stream and multi-stream scalability
	modes.		modes.
	2. Conventions and Terminology		2. Conventions and Terminology
	skipping to change at line 126 ¶		skipping to change at line 128 ¶
	The spatial layer refresh of an enhancement layer is shown below.		The spatial layer refresh of an enhancement layer is shown below.
	The "<--" indicates a coding dependency.		The "<--" indicates a coding dependency.
	... <-- S1 <-- S1 S1 <-- S1 <-- ...		... <-- S1 <-- S1 S1 <-- S1 <-- ...
	| | | |		| | | |
	\/ \/ \/ \/		\/ \/ \/ \/
	... <-- S0 <-- S0 <-- S0 <-- S0 <-- ...		... <-- S0 <-- S0 <-- S0 <-- S0 <-- ...
	1 2 3 4		1 2 3 4
	Figure 1		Figure 1: Refresh of a Spatial Enhancement Layer
	In Figure 1, frame 3 is a layer refresh point for spatial layer S1; a		In Figure 1, frame 3 is a layer refresh point for spatial layer S1; a
	decoder that had previously only been decoding spatial layer S0 would		decoder that had previously only been decoding spatial layer S0 would
	be able to decode layer S1 starting at frame 3.		be able to decode layer S1 starting at frame 3.
	The spatial layer refresh of a base layer is shown below. The "<--"		The spatial layer refresh of a base layer is shown below. The "<--"
	indicates a coding dependency.		indicates a coding dependency.
	... <-- S1 <-- S1 <-- S1 <-- S1 <-- ...		... <-- S1 <-- S1 <-- S1 <-- S1 <-- ...
	| | | |		| | | |
	\/ \/ \/ \/		\/ \/ \/ \/
	... <-- S0 <-- S0 S0 <-- S0 <-- ...		... <-- S0 <-- S0 S0 <-- S0 <-- ...
	1 2 3 4		1 2 3 4
	Figure 2		Figure 2: Refresh of a Spatial Base Layer
	In Figure 2, frame 3 is a layer refresh point for spatial layer S0; a		In Figure 2, frame 3 is a layer refresh point for spatial layer S0; a
	decoder that had previously not been decoding the stream at all could		decoder that had previously not been decoding the stream at all could
	decode layer S0 starting at frame 3.		decode layer S0 starting at frame 3.
	For temporal layers, while normal encoding allows frames to depend on		For temporal layers, while normal encoding allows frames to depend on
	earlier frames of the same temporal layer, layer refresh requires		earlier frames of the same temporal layer, layer refresh requires
	that the layer be "temporally nested", i.e., use as reference only		that the layer be "temporally nested", i.e., use as reference only
	earlier frames of a lower temporal layer, not any earlier frames of		earlier frames of a lower temporal layer, not any earlier frames of
	this temporal layer and promise that no future frames of this		this temporal layer and promise that no future frames of this
	skipping to change at line 168 ¶		skipping to change at line 170 ¶
	The temporal layer refresh is shown below. The "<--" indicates a		The temporal layer refresh is shown below. The "<--" indicates a
	coding dependency.		coding dependency.
	... <----- T1 <------ T1 T1 <------ ...		... <----- T1 <------ T1 T1 <------ ...
	/ / /		/ / /
	|_ |_ |_		|_ |_ |_
	... <-- T0 <------ T0 <------ T0 <------ T0 <--- ...		... <-- T0 <------ T0 <------ T0 <------ T0 <--- ...
	1 2 3 4 5 6 7		1 2 3 4 5 6 7
	Figure 3		Figure 3: Refresh of a Temporal Layer
	In Figure 3, frame 6 is a layer refresh point for temporal layer T1;		In Figure 3, frame 6 is a layer refresh point for temporal layer T1;
	a decoder that had previously only been decoding temporal layer T0		a decoder that had previously only been decoding temporal layer T0
	would be able to decode layer T1 starting at frame 6.		would be able to decode layer T1 starting at frame 6.
	An inherently temporally nested stream is shown below. The "<--"		An inherently temporally nested stream is shown below. The "<--"
	indicates a coding dependency.		indicates a coding dependency.
	T1 T1 T1		T1 T1 T1
	/ / /		/ / /
	|_ |_ |_		|_ |_ |_
	... <-- T0 <------ T0 <------ T0 <------ T0 <--- ...		... <-- T0 <------ T0 <------ T0 <------ T0 <--- ...
	1 2 3 4 5 6 7		1 2 3 4 5 6 7
	Figure 4		Figure 4: An Inherently Temporally-Nested Stream
	In Figure 4, the stream is temporally nested in its ordinary		In Figure 4, the stream is temporally nested in its ordinary
	structure; a decoder receiving layer T0 can begin decoding layer T1		structure; a decoder receiving layer T0 can begin decoding layer T1
	at any point.		at any point.
	A "layer index" is a numeric label for a specific spatial and		A "layer index" is a numeric label for a specific spatial and
	temporal layer of a scalable stream. It consists of both a "temporal		temporal layer of a scalable stream. It consists of both a "temporal
	ID" identifying the temporal layer and a "layer ID" identifying the		ID" identifying the temporal layer and a "layer ID" identifying the
	spatial or quality layer. The details of how layers of a scalable		spatial or quality layer. The details of how layers of a scalable
	stream are labeled are codec specific. Details for several codecs		stream are labeled are codec specific. Details for several codecs
	skipping to change at line 236 ¶		skipping to change at line 238 ¶
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| SSRC |		| SSRC |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Seq nr. |C| Payload Type| Reserved |		| Seq nr. |C| Payload Type| Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| RES | TTID| TLID | RES | CTID| CLID |		| RES | TTID| TLID | RES | CTID| CLID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 5		Figure 5: Layer Refresh Request FCI Format
	Synchronization Source (SSRC) (32 bits):		Synchronization Source (SSRC) (32 bits):
	The SSRC value of the media sender that is requested to send a		The SSRC value of the media sender that is requested to send a
	layer refresh point.		layer refresh point.
	Seq nr. (8 bits):		Seq nr. (8 bits):
	The command sequence number. The sequence number space is unique		The command sequence number. The sequence number space is unique
	for each pairing of the SSRC of command source and the SSRC of the		for each pairing of the SSRC of command source and the SSRC of the
	command target. The sequence number SHALL be increased by 1 for		command target. The sequence number SHALL be increased by 1 for
	each new command (modulo 256, so the value after 255 is 0). A		each new command (modulo 256, so the value after 255 is 0). A
	skipping to change at line 292 ¶		skipping to change at line 294 ¶
	If C is 1, the layer ID of the current spatial or quality layer		If C is 1, the layer ID of the current spatial or quality layer
	being decoded by the receiver. This message is not requesting		being decoded by the receiver. This message is not requesting
	refresh of layers at or below this layer. If C is 0, this field		refresh of layers at or below this layer. If C is 0, this field
	SHALL be set to 0 by the sender and SHALL be ignored on reception.		SHALL be set to 0 by the sender and SHALL be ignored on reception.
	When C is 1, TTID MUST NOT be less than CTID, and TLID MUST NOT be		When C is 1, TTID MUST NOT be less than CTID, and TLID MUST NOT be
	less than CLID; at least one of either TTID or TLID MUST be greater		less than CLID; at least one of either TTID or TLID MUST be greater
	than CTID or CLID, respectively. That is to say, the target layer		than CTID or CLID, respectively. That is to say, the target layer
	index <TTID, TLID> MUST be a layer upgrade from the current layer		index <TTID, TLID> MUST be a layer upgrade from the current layer
	index <CTID, CLID>. A sender MAY request an upgrade in both temporal		index <CTID, CLID>. A sender MAY request an upgrade in both temporal
	and spatial/quality layers simultaneously.		and spatial or quality layers simultaneously.
	A receiver receiving an LRR feedback packet that does not satisfy the		A receiver receiving an LRR feedback packet that does not satisfy the
	requirements of the previous paragraph, i.e., one where the C bit is		requirements of the previous paragraph, i.e., one where the C bit is
	present but the TTID is less than the CTID or the TLID is less than		present but the TTID is less than the CTID or the TLID is less than
	the CLID, MUST discard the request.		the CLID, MUST discard the request.
	Note: the syntax of the TTID, TLID, CTID, and CLID fields match, by		| Note: The syntax of the TTID, TLID, CTID, and CLID fields
	design, the TID and LID fields in [RFC9626].		| match, by design, the TID and LID fields in [RFC9626].
	3.2. Semantics		3.2. Semantics
	Within the common packet header for feedback messages (as defined in		Within the common packet header for feedback messages (as defined in
	Section 6.1 of [RFC4585]), the "SSRC of packet sender" field		Section 6.1 of [RFC4585]), the "SSRC of packet sender" field
	indicates the source of the request, and the "SSRC of media source"		indicates the source of the request, and the "SSRC of media source"
	is not used and SHALL be set to 0. The SSRCs of the media senders to		is not used and SHALL be set to 0. The SSRCs of the media senders to
	which the LRR command applies are in the corresponding FCI entries.		which the LRR command applies are in the corresponding FCI entries.
	An LRR message MAY contain requests to multiple media senders, using		An LRR message MAY contain requests to multiple media senders, using
	one FCI entry per target media sender.		one FCI entry per target media sender.
	skipping to change at line 336 ¶		skipping to change at line 338 ¶
	previously had been discarding.		previously had been discarding.
	4. Usage with Specific Codecs		4. Usage with Specific Codecs
	In order for an LRR to be used with a scalable codec, the format of		In order for an LRR to be used with a scalable codec, the format of
	the temporal and layer ID fields (for both the target and current		the temporal and layer ID fields (for both the target and current
	layer indices) needs to be specified for that codec's RTP		layer indices) needs to be specified for that codec's RTP
	packetization. New RTP packetization specifications for scalable		packetization. New RTP packetization specifications for scalable
	codecs SHOULD define how this is done. (The VP9 payload [RFC9628],		codecs SHOULD define how this is done. (The VP9 payload [RFC9628],
	for instance, has done so.) If the payload also specifies how it is		for instance, has done so.) If the payload also specifies how it is
	used with the Frame Marking RTP Header Extension [RFC9626], the		used with the Video Frame Marking RTP Header Extension described in
	syntax MUST be defined in the same manner as the TID and LID fields		[RFC9626], the syntax MUST be defined in the same manner as the TID
	in that header.		and LID fields in that header.
	4.1. H264 SVC		4.1. H264 SVC
	H.264 SVC [RFC6190] defines temporal, dependency (spatial), and		H.264 SVC [RFC6190] defines temporal, dependency (spatial), and
	quality scalability modes.		quality scalability modes.
	+---------------+---------------+		+---------------+---------------+
	|0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7|		|0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| RES | TID |R| DID | QID |		| RES | TID |R| DID | QID |
	+---------------+---------------+		+---------------+---------------+
	Figure 6		Figure 6: H.264 SVC Layer Index Fields Format
	Figure 6 shows the format of the layer index fields for H.264 SVC		Figure 6 shows the format of the layer index fields for H.264 SVC
	streams. The "R" and "RES" fields MUST be set to 0 on transmission		streams. The "R" and "RES" fields MUST be set to 0 on transmission
	and ignored on reception. See Section 1.1.3 of [RFC6190] for details		and ignored on reception. See Section 1.1.3 of [RFC6190] for details
	on the dependency_id (DID), quality_id (QID), and temporal_id (TID)		on the dependency_id (DID), quality_id (QID), and temporal_id (TID)
	fields.		fields.
	A dependency or quality layer refresh of a given layer in H.264 SVC		A dependency or quality layer refresh of a given layer in H.264 SVC
	can be identified by the "I" bit (idr_flag) in the extended Network		can be identified by the "I" bit (idr_flag) in the extended Network
	Abstraction Layer (NAL) unit header, present in NAL unit types 14		Abstraction Layer (NAL) unit header, present in NAL unit types 14
	skipping to change at line 411 ¶		skipping to change at line 413 ¶
	The VP8 RTP payload format [RFC7741] defines temporal scalability		The VP8 RTP payload format [RFC7741] defines temporal scalability
	modes. It does not support spatial scalability.		modes. It does not support spatial scalability.
	+---------------+---------------+		+---------------+---------------+
	|0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7|		|0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| RES | TID | RES |		| RES | TID | RES |
	+---------------+---------------+		+---------------+---------------+
	Figure 7		Figure 7: VP8 Layer Index Field Format
	Figure 7 shows the format of the layer index field for VP8 streams.		Figure 7 shows the format of the layer index field for VP8 streams.
	The "RES" fields MUST be set to 0 on transmission and be ignored on		The "RES" fields MUST be set to 0 on transmission and be ignored on
	reception. See Section 4.2 of [RFC7741] for details on the TID		reception. See Section 4.2 of [RFC7741] for details on the TID
	field.		field.
	A VP8 layer refresh point can be identified by the presence of the		A VP8 layer refresh point can be identified by the presence of the
	"Y" bit in the VP8 payload header. When this bit is set, this and		"Y" bit in the VP8 payload header. When this bit is set, this and
	all subsequent frames depend only on the current base temporal layer.		all subsequent frames depend only on the current base temporal layer.
	On receipt of an LRR for a VP8 stream, a sender that supports LRRs		On receipt of an LRR for a VP8 stream, a sender that supports LRRs
	skipping to change at line 445 ¶		skipping to change at line 447 ¶
	temporal scalability, with protocol elements reserved for spatial or		temporal scalability, with protocol elements reserved for spatial or
	other scalability modes (which are expected to be defined in a future		other scalability modes (which are expected to be defined in a future
	version of the specification).		version of the specification).
	+---------------+---------------+		+---------------+---------------+
	|0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7|		|0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| RES | TID |RES| LayerId |		| RES | TID |RES| LayerId |
	+---------------+---------------+		+---------------+---------------+
	Figure 8		Figure 8: H.265 Layer Index Fields Format
	Figure 8 shows the format of the layer index field for H.265 streams.		Figure 8 shows the format of the layer index field for H.265 streams.
	The "RES" fields MUST be set to 0 on transmission and ignored on		The "RES" fields MUST be set to 0 on transmission and ignored on
	reception. See Section 1.1.4 of [RFC7798] for details on the LayerId		reception. See Section 1.1.4 of [RFC7798] for details on the LayerId
	and TID fields.		and TID fields.
	H.265 streams signal whether they are temporally nested by using the		H.265 streams signal whether they are temporally nested by using the
	vps_temporal_id_nesting_flag in the Video Parameter Set (VPS) and the		vps_temporal_id_nesting_flag in the Video Parameter Set (VPS) and the
	sps_temporal_id_nesting_flag in the Sequence Parameter Set (SPS). If		sps_temporal_id_nesting_flag in the Sequence Parameter Set (SPS). If
	this flag is set in a stream's currently applicable VPS or SPS,		this flag is set in a stream's currently applicable VPS or SPS,
	skipping to change at line 488 ¶		skipping to change at line 490 ¶
	spatial layer refresh of a specific layer can be identified by NAL		spatial layer refresh of a specific layer can be identified by NAL
	units with the requested layer ID and NAL unit types between 16 and		units with the requested layer ID and NAL unit types between 16 and
	21, inclusive. A dependency or quality layer refresh is complete		21, inclusive. A dependency or quality layer refresh is complete
	once NAL units of this type have been seen on all the appropriate		once NAL units of this type have been seen on all the appropriate
	layers (in decoding order) above the current layer index (if any, or		layers (in decoding order) above the current layer index (if any, or
	beginning from the base layer if not) through the target layer index.		beginning from the base layer if not) through the target layer index.
	5. Usage with Different Scalability Transmission Mechanisms		5. Usage with Different Scalability Transmission Mechanisms
	Several different mechanisms are defined for how scalable streams can		Several different mechanisms are defined for how scalable streams can
	be transmitted in RTP. The RTP Taxonomy (Section 3.7 of [RFC7656])		be transmitted in RTP. Section 3.7 of "A Taxonomy of Semantics and
			Mechanisms for Real-Time Transport Protocol (RTP) Sources" [RFC7656]
	defines three mechanisms: Single RTP stream on a Single media		defines three mechanisms: Single RTP stream on a Single media
	Transport (SRST), Multiple RTP streams on a Single media Transport		Transport (SRST), Multiple RTP streams on a Single media Transport
	(MRST), and Multiple RTP streams on Multiple media Transports (MRMT).		(MRST), and Multiple RTP streams on Multiple media Transports (MRMT).
	The LRR message is applicable to all these mechanisms. For MRST and		The LRR message is applicable to all these mechanisms. For MRST and
	MRMT mechanisms, the "media source" field of the LRR FCI is set to		MRMT mechanisms, the "media source" field of the LRR FCI is set to
	the SSRC of the RTP stream containing the layer indicated by the		the SSRC of the RTP stream containing the layer indicated by the
	Current Layer Index (if "C" is 1) or the stream containing the base		Current Layer Index (if "C" is 1) or the stream containing the base
	encoded stream (if "C" is 0). For MRMT, it is sent on the RTP		encoded stream (if "C" is 0). For MRMT, the LRR message is sent on
	session on which this stream is sent. On receipt, the sender MUST		the RTP session on which this stream is sent. On receipt, the sender
	refresh all the layers requested in the stream, simultaneously in		MUST refresh all the layers requested in the stream, simultaneously
	decode order.		in decode order.
	6. SDP Definitions		6. SDP Definitions
	Section 7 of [RFC5104] defines Session Description Protocol (SDP)		Section 7 of [RFC5104] defines Session Description Protocol (SDP)
	procedures for indicating and negotiating support for Codec Control		procedures for indicating and negotiating support for Codec Control
	Messages (CCM) in SDP. This document extends this with a new codec		Messages (CCM) in SDP. This document extends this with a new codec
	control command, "lrr", which indicates support of the LRR.		control command, "lrr", which indicates support of the LRR.
	Figure 9 gives a formal Augmented Backus-Naur Form (ABNF) [RFC5234]		Figure 9 gives a formal Augmented Backus-Naur Form (ABNF) [RFC5234]
	showing this grammar extension, extending the grammar defined in		showing this grammar extension, extending the grammar defined in
	skipping to change at line 625 ¶		skipping to change at line 628 ¶
	<https://www.rfc-editor.org/info/rfc8082>.		<https://www.rfc-editor.org/info/rfc8082>.
	[RFC9628] Lennox, J., Hong, D., Uberti, J., Holmer, S., and M.		[RFC9628] Lennox, J., Hong, D., Uberti, J., Holmer, S., and M.
	Flodman, "The Layer Refresh Request (LRR) RTCP Feedback		Flodman, "The Layer Refresh Request (LRR) RTCP Feedback
	Message", RFC 9628, DOI 10.17487/RFC9628, August 2024,		Message", RFC 9628, DOI 10.17487/RFC9628, August 2024,
	<https://www.rfc-editor.org/info/rfc9628>.		<https://www.rfc-editor.org/info/rfc9628>.
	Authors' Addresses		Authors' Addresses
	Jonathan Lennox		Jonathan Lennox
	Vidyo, Inc.		8x8, Inc. / Jitsi
	433 Hackensack Avenue		Jersey City, NJ 07302
	Seventh Floor
	Hackensack, NJ 07601
	United States of America		United States of America
	Email: jonathan@vidyo.com		Email: jonathan.lennox@8x8.com
	Danny Hong		Danny Hong
	Vidyo, Inc.		Vidyo, Inc.
	433 Hackensack Avenue		433 Hackensack Avenue
	Seventh Floor		Seventh Floor
	Hackensack, NJ 07601		Hackensack, NJ 07601
	United States of America		United States of America
	Email: danny@vidyo.com		Email: danny@vidyo.com
	Justin Uberti		Justin Uberti
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