rfc9626v1.txt		rfc9626.txt
	Internet Engineering Task Force (IETF) M. Zanaty		Internet Engineering Task Force (IETF) M. Zanaty
	Request for Comments: 9626 E. Berger		Request for Comments: 9626 E. Berger
	Category: Experimental S. Nandakumar		Category: Experimental S. Nandakumar
	ISSN: 2070-1721 Cisco Systems		ISSN: 2070-1721 Cisco Systems
	August 2024		February 2025
	Video Frame Marking RTP Header Extension		Video Frame Marking RTP Header Extension
	Abstract		Abstract
	This document describes a Video Frame Marking RTP header extension		This document describes a Video Frame Marking RTP header extension
	used to convey information about video frames that is critical for		used to convey information about video frames that is critical for
	error recovery and packet forwarding in RTP middleboxes or network		error recovery and packet forwarding in RTP middleboxes or network
	nodes. It is most useful when media is encrypted and essential when		nodes. It is most useful when media is encrypted and essential when
	the middlebox or node has no access to the media decryption keys. It		the middlebox or node has no access to the media decryption keys. It
	skipping to change at line 41 ¶		skipping to change at line 41 ¶
	publication by the Internet Engineering Steering Group (IESG). Not		publication by the Internet Engineering Steering Group (IESG). Not
	all documents approved by the IESG are candidates for any level of		all documents approved by the IESG are candidates for any level of
	Internet Standard; see Section 2 of RFC 7841.		Internet Standard; see 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/rfc9626.		https://www.rfc-editor.org/info/rfc9626.
	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
	in the Revised BSD License.		in the Revised BSD License.
	Table of Contents		Table of Contents
	1. Introduction		1. Introduction
	2. Requirements Language		2. Requirements Language
	3. Frame Marking RTP Header Extension		3. Video Frame Marking RTP Header Extension
	3.1. Long Extension for Scalable Streams		3.1. Long Extension for Scalable Streams
	3.2. Short Extension for Non-scalable Streams		3.2. Short Extension for Non-Scalable Streams
	3.3. LID Mappings for Scalable Streams		3.3. LID Mappings for Scalable Streams
	3.3.1. VP9 LID Mapping		3.3.1. VP9 LID Mapping
	3.3.2. H265 LID Mapping		3.3.2. H265 LID Mapping
	3.3.3. H264 Scalable Video Coding (SVC) LID Mapping		3.3.3. H264 Scalable Video Coding (SVC) LID Mapping
	3.3.4. H264 Advanced Video Coding (AVC) LID Mapping		3.3.4. H264 Advanced Video Coding (AVC) LID Mapping
	3.3.5. VP8 LID Mapping		3.3.5. VP8 LID Mapping
	3.3.6. Future Codec LID Mapping		3.3.6. Future Codec LID Mapping
	3.4. Signaling Information		3.4. Signaling Information
	3.5. Usage Considerations		3.5. Usage Considerations
	3.5.1. Relation to Layer Refresh Request (LRR)		3.5.1. Relation to Layer Refresh Request (LRR)
	skipping to change at line 157 ¶		skipping to change at line 157 ¶
	specifies the necessary meta-information in an RTP header extension.		specifies the necessary meta-information in an RTP header extension.
	2. Requirements Language		2. Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all		BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	3. Frame Marking RTP Header Extension		3. Video Frame Marking RTP Header Extension
	This specification uses RTP header extensions as defined in		This specification uses RTP header extensions as defined in
	[RFC8285]. A subset of meta-information from the video stream is		[RFC8285]. A subset of meta-information from the video stream is
	provided as an RTP header extension to allow an RTP switch to do		provided as an RTP header extension to allow an RTP switch to do
	generic selective forwarding of video streams encoded with		generic selective forwarding of video streams encoded with
	potentially different video codecs.		potentially different video codecs.
	The Frame Marking RTP header extension is encoded using the one-byte		The Video Frame Marking RTP header extension is encoded using the
	header or two-byte header as described in [RFC8285]. The one-byte		one-byte header or two-byte header as described in [RFC8285]. The
	header format is used for examples in this document. The two-byte		one-byte header format is used for examples in this document. The
	header format is used when other two-byte header extensions are		two-byte header format is used when other two-byte header extensions
	present in the same RTP packet since mixing one-byte and two-byte		are present in the same RTP packet since mixing one-byte and two-byte
	extensions is not possible in the same RTP packet.		extensions is not possible in the same RTP packet.
	This extension is only specified for Source (not Redundancy) RTP		This extension is only specified for Source (not Redundancy) RTP
	Streams [RFC7656] that carry video payloads. It is not specified for		Streams [RFC7656] that carry video payloads. It is not specified for
	audio payloads, nor is it specified for Redundancy RTP Streams. The		audio payloads, nor is it specified for Redundancy RTP Streams. The
	(separate) specifications for Redundancy RTP Streams often include		(separate) specifications for Redundancy RTP Streams often include
	provisions for recovering any header extensions that were part of the		provisions for recovering any header extensions that were part of the
	original source packet. Such provisions can be followed to recover		original source packet. Such provisions can be followed to recover
	the Frame Marking RTP header extension of the original source packet.		the Video Frame Marking RTP header extension of the original source
	Source packet frame markings may be useful when generating Redundancy		packet. Source packet frame markings may be useful when generating
	RTP Streams; for example, the I (Independent Frame) and D		Redundancy RTP Streams; for example, the I (Independent Frame) and D
	(Discardable Frame) bits, defined in Section 3.1, can be used to		(Discardable Frame) bits, defined in Section 3.1, can be used to
	generate extra or no redundancy, respectively, and redundancy schemes		generate extra or no redundancy, respectively, and redundancy schemes
	with source blocks can align source block boundaries with independent		with source blocks can align source block boundaries with independent
	frame boundaries as marked by the I bit.		frame boundaries as marked by the I bit.
	A frame, in the context of this specification, is the set of RTP		A frame, in the context of this specification, is the set of RTP
	packets with the same RTP timestamp from a specific RTP		packets with the same RTP timestamp from a specific RTP
	Synchronization Source (SSRC). A frame within a layer is the set of		Synchronization Source (SSRC). A frame within a layer is the set of
	RTP packets with the same RTP timestamp, SSRC, Temporal ID (TID), and		RTP packets with the same RTP timestamp, SSRC, Temporal-layer ID
	Layer ID (LID).		(TID), and Layer ID (LID).
	3.1. Long Extension for Scalable Streams		3.1. Long Extension for Scalable Streams
	The following RTP header extension is RECOMMENDED for scalable		The following RTP header extension is RECOMMENDED for scalable
	streams. It MAY also be used for non-scalable streams, in which case		streams. It MAY also be used for non-scalable streams, in which case
	the TID, LID, and TL0PICIDX MUST be 0 or omitted. The ID is assigned		the TID, LID, and TL0PICIDX MUST be 0 or omitted. The ID is assigned
	per [RFC8285]. The length is encoded as follows:		per [RFC8285]. The length is encoded as follows:
	* L=2 to indicate 3 octets of data when nothing is omitted,		* L=2 to indicate 3 octets of data when nothing is omitted,
	skipping to change at line 220 ¶		skipping to change at line 220 ¶
	or		or
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ID=? | L=1 |S|E|I|D|B| TID | LID | (TL0PICIDX omitted)		| ID=? | L=1 |S|E|I|D|B| TID | LID | (TL0PICIDX omitted)
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	or		or
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ID=? | L=0 |S|E|I|D|B| TID | (LID and TL0PICIDX omitted)		| ID=? | L=0 |S|E|I|D|B| TID | (LID and TL0PICIDX omitted)
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The following information is extracted from the media payload and		The following information is extracted from the media payload and
	sent in the Frame Marking RTP header extension.		sent in the Video Frame Marking RTP header extension.
	S: Start of Frame (1 bit)		S: Start of Frame (1 bit)
	MUST be 1 in the first packet in a frame within a layer;		MUST be 1 in the first packet in a frame within a layer;
	otherwise, MUST be 0.		otherwise, MUST be 0.
	E: End of Frame (1 bit)		E: End of Frame (1 bit)
	MUST be 1 in the last packet in a frame within a layer; otherwise,		MUST be 1 in the last packet in a frame within a layer; otherwise,
	MUST be 0. Note that the RTP header marker bit MAY be used to		MUST be 0. Note that the RTP header marker bit MAY be used to
	infer the last packet of the highest enhancement layer in payload		infer the last packet of the highest enhancement layer in payload
	formats with such semantics.		formats with such semantics.
	skipping to change at line 253 ¶		skipping to change at line 253 ¶
	MUST be 1 for a frame within a layer the sender knows can be		MUST be 1 for a frame within a layer the sender knows can be
	discarded and still provide a decodable media stream; otherwise,		discarded and still provide a decodable media stream; otherwise,
	MUST be 0.		MUST be 0.
	B: Base Layer Sync (1 bit)		B: Base Layer Sync (1 bit)
	When the TID is not 0, this MUST be 1 if the sender knows this		When the TID is not 0, this MUST be 1 if the sender knows this
	frame within a layer only depends on the base temporal layer;		frame within a layer only depends on the base temporal layer;
	otherwise, MUST be 0. When the TID is 0 or if no scalability is		otherwise, MUST be 0. When the TID is 0 or if no scalability is
	used, this MUST be 0.		used, this MUST be 0.
	TID: Temporal ID (3 bits)		TID: Temporal-layer ID (3 bits)
	Identifies the temporal layer/sub-layer encoded, starting with 0		Identifies the temporal layer/sub-layer encoded, starting with 0
	for the base layer and increasing with higher temporal fidelity.		for the base layer and increasing with higher temporal fidelity.
	If no scalability is used, this MUST be 0. It is implicitly 0 in		If no scalability is used, this MUST be 0. It is implicitly 0 in
	the short extension format.		the short extension format.
	LID: Layer ID (8 bits)		LID: Layer ID (8 bits)
	Identifies the spatial and quality layer encoded, starting with 0		Identifies the spatial and quality layer encoded, starting with 0
	for the base layer and increasing with higher fidelity. If no		for the base layer and increasing with higher fidelity. If no
	scalability is used, this MUST be 0 or omitted to reduce length.		scalability is used, this MUST be 0 or omitted to reduce length.
	When the LID is omitted, TL0PICIDX MUST also be omitted. It is		When the LID is omitted, TL0PICIDX MUST also be omitted. It is
	skipping to change at line 302 ¶		skipping to change at line 302 ¶
	With further information, for example, possible future RTCP source		With further information, for example, possible future RTCP source
	description (SDES) items that convey full layer structure		description (SDES) items that convey full layer structure
	information, it may be possible to map these TIDs and LIDs to		information, it may be possible to map these TIDs and LIDs to
	specific absolute frame rates, resolutions, bitrates, and explicit		specific absolute frame rates, resolutions, bitrates, and explicit
	dependencies between layers. Such additional layer information may		dependencies between layers. Such additional layer information may
	be useful for forwarding decisions in the RTP switch but is beyond		be useful for forwarding decisions in the RTP switch but is beyond
	the scope of this memo. The relative layer information is still		the scope of this memo. The relative layer information is still
	useful for many selective forwarding decisions, even without such		useful for many selective forwarding decisions, even without such
	additional layer information.		additional layer information.
	3.2. Short Extension for Non-scalable Streams		3.2. Short Extension for Non-Scalable Streams
	The following RTP header extension is RECOMMENDED for non-scalable		The following RTP header extension is RECOMMENDED for non-scalable
	streams. It is identical to the shortest form of the extension for		streams. It is identical to the shortest form of the extension for
	scalable streams, except the last four bits (B and TID) are replaced		scalable streams, except the last four bits (B and TID) are replaced
	with zeros. It MAY also be used for scalable streams if the sender		with zeros. It MAY also be used for scalable streams if the sender
	has limited or no information about stream scalability. The ID is		has limited or no information about stream scalability. The ID is
	assigned per [RFC8285]; the length is encoded as L=0, which indicates		assigned per [RFC8285]; the length is encoded as L=0, which indicates
	1 octet of data.		1 octet of data.
	0 1		0 1
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ID=? | L=0 |S|E|I|D|0 0 0 0|		| ID=? | L=0 |S|E|I|D|0 0 0 0|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The following information is extracted from the media payload and		The following information is extracted from the media payload and
	sent in the Frame Marking RTP header extension.		sent in the Video Frame Marking RTP header extension.
	S: Start of Frame (1 bit)		S: Start of Frame (1 bit)
	MUST be 1 in the first packet in a frame; otherwise, MUST be 0.		MUST be 1 in the first packet in a frame; otherwise, MUST be 0.
	E: End of Frame (1 bit)		E: End of Frame (1 bit)
	MUST be 1 in the last packet in a frame; otherwise, MUST be 0.		MUST be 1 in the last packet in a frame; otherwise, MUST be 0.
	SHOULD match the RTP header marker bit in payload formats with		SHOULD match the RTP header marker bit in payload formats with
	such semantics for marking end of frame.		such semantics for marking end of frame.
	I: Independent Frame (1 bit)		I: Independent Frame (1 bit)
	skipping to change at line 341 ¶		skipping to change at line 341 ¶
	prior frames, e.g., intra-frame, VPX keyframe, H.264 IDR		prior frames, e.g., intra-frame, VPX keyframe, H.264 IDR
	[RFC6184], or H.265 IDR/CRA/BLA/IRAP [RFC7798]; otherwise, MUST be		[RFC6184], or H.265 IDR/CRA/BLA/IRAP [RFC7798]; otherwise, MUST be
	0.		0.
	D: Discardable Frame (1 bit)		D: Discardable Frame (1 bit)
	MUST be 1 for frames the sender knows can be discarded and still		MUST be 1 for frames the sender knows can be discarded and still
	provide a decodable media stream; otherwise, MUST be 0.		provide a decodable media stream; otherwise, MUST be 0.
	The remaining (4 bits)		The remaining (4 bits)
	These are reserved/fixed values and not used for non-scalable		These are reserved/fixed values and not used for non-scalable
	streams; they MUST be set to 0 upon transmission and ignored upon		streams; they MUST be set to zero upon transmission and ignored
	reception.		upon reception.
	3.3. LID Mappings for Scalable Streams		3.3. LID Mappings for Scalable Streams
	This section maps the specific Layer ID (LID) information contained		This section maps the specific Layer ID (LID) information contained
	in specific scalable codecs to the generic LID and TID fields.		in specific scalable codecs to the generic LID and TID fields.
	Note that non-scalable streams have no LID information; thus, they		Note that non-scalable streams have no LID information; thus, they
	have no mappings.		have no mappings.
	3.3.1. VP9 LID Mapping		3.3.1. VP9 LID Mapping
	The VP9 [RFC9628] Spatial Layer ID (SID, 3 bits) and Temporal Layer		The VP9 [RFC9628] Spatial-layer ID (SID, 3 bits) and Temporal-layer
	ID (TID, 3 bits) in the VP9 payload descriptor are mapped to the		ID (TID, 3 bits) in the VP9 payload descriptor are mapped to the
	generic LID and TID fields in the header extension as shown in the		generic LID and TID fields in the header extension as shown in the
	following figure.		following figure.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0| SID | TL0PICIDX |		| ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0| SID | TL0PICIDX |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The S bit MUST match the B bit in the VP9 payload descriptor.		The S bit MUST match the B bit in the VP9 payload descriptor.
	The E bit MUST match the E bit in the VP9 payload descriptor.		The E bit MUST match the E bit in the VP9 payload descriptor.
	The I bit MUST match the inverse of the P bit in the VP9 payload		The I bit MUST match the inverse of the P bit in the VP9 payload
	descriptor.		descriptor.
	The D bit MUST be 1 if the refresh_frame_flags in the VP9 payload		The D bit MUST be 1 if the refresh_frame_flags bits in the VP9
	uncompressed header are all 0; otherwise, it MUST be 0.		payload uncompressed header are all 0; otherwise, it MUST be 0.
	The B bit MUST be 0 if the TID is 0; if the TID is not 0, it MUST		The B bit MUST be 0 if the TID is 0; if the TID is not 0, it MUST
	match the U bit in the VP9 payload descriptor. Note: when using		match the U bit in the VP9 payload descriptor.
	temporally nested scalability structures as recommended in
	Section 3.5.2, the B bit and VP9 U bit will always be 1 if the TID is		| Note: when using temporally nested scalability structures as
	not 0 since it is always possible to switch up to a higher temporal		| recommended in Section 3.5.2, the B bit and VP9 U bit will
	layer in such nested structures.		| always be 1 if the TID is not 0 since it is always possible to
			| switch up to a higher temporal layer in such nested structures.
	The TID, SID, and TL0PICIDX MUST match the correspondingly named		The TID, SID, and TL0PICIDX MUST match the correspondingly named
	fields in the VP9 payload descriptor, with SID aligned in the least		fields in the VP9 payload descriptor, with SID aligned in the least
	significant 3 bits of the 8-bit LID field and zeros in the most		significant 3 bits of the 8-bit LID field and zeros in the most
	significant 5 bits.		significant 5 bits.
	3.3.2. H265 LID Mapping		3.3.2. H265 LID Mapping
	The H265 [RFC7798] LayerID (6 bits), and TID (3 bits) from the		The H265 [RFC7798] layer ID (6 bits), and TID (3 bits) from the
	Network Abstraction Layer (NAL) unit header are mapped to the generic		Network Abstraction Layer (NAL) unit header are mapped to the generic
	LID and TID fields in the header extension as shown in the following		LID and TID fields in the header extension as shown in the following
	figure.		figure.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ID=? | L=2 |S|E|I|D|B| TID |0|0| LayerID | TL0PICIDX |		| ID=? | L=2 |S|E|I|D|B| TID |0|0| layer ID | TL0PICIDX |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The S and E bits MUST match the correspondingly named bits in		The S and E bits MUST match the correspondingly named bits in
	PACI:PHES:TSCI payload structures.		PACI:PHES:TSCI payload structures.
	The I bit MUST be 1 when the NAL unit type is 16-23 (inclusive) or		The I bit MUST be 1 when the NAL unit type is 16-23 (inclusive) or
	32-34 (inclusive), or an aggregation packet or fragmentation unit		32-34 (inclusive), or an aggregation packet or fragmentation unit
	encapsulating any of these types; otherwise, it MUST be 0. These		encapsulating any of these types; otherwise, it MUST be 0. These
	ranges cover intra (IRAP) frames as well as critical parameter sets		ranges cover intra (IRAP) frames as well as critical parameter sets
	(Video Parameter Set (VPS), Sequence Parameter Set (SPS), Picture		(Video Parameter Set (VPS), Sequence Parameter Set (SPS), Picture
	Parameter Set (PPS)).		Parameter Set (PPS)).
	The D bit MUST be 1 when the NAL unit type is 0, 2, 4, 6, 8, 10, 12,		The D bit MUST be 1 if either:
	14, 38, or an aggregation packet or fragmentation unit encapsulating
	only these types; otherwise, it MUST be 0. These ranges cover non-		* the payload's NAL unit header's NRI field is 0, or
	reference frames as well as filler data.
			* the payload is an aggregation packet or fragmentation unit
			encapsulating only NAL units with NRI = 0.
			Otherwise, it MUST be 0.
			These ranges cover non-reference frames as well as filler data.
	The B bit cannot be determined reliably from simple inspection of		The B bit cannot be determined reliably from simple inspection of
	payload headers; therefore, it is determined by implementation-		payload headers; therefore, it is determined by implementation-
	specific means. For example, internal codec interfaces may provide		specific means. For example, internal codec interfaces may provide
	information to set this reliably.		information to set this reliably.
	The TID and LayerID MUST match the correspondingly named fields in		The TID and layer ID MUST match the correspondingly named fields in
	the H265 NAL unit header, with LayerID aligned in the least		the H265 NAL unit header, with layer ID aligned in the least
	significant 6 bits of the 8-bit LID field and zeros in the most		significant 6 bits of the 8-bit LID field and zeros in the most
	significant 2 bits.		significant 2 bits.
	3.3.3. H264 Scalable Video Coding (SVC) LID Mapping		3.3.3. H264 Scalable Video Coding (SVC) LID Mapping
	The following shows H264-SVC [RFC6190] Layer encoding information (3		The following shows H264-SVC [RFC6190] Layer encoding information (3
	bits for spatial/dependency layer, 4 bits for quality layer, and 3		bits for spatial/dependency layer, 4 bits for quality layer, and 3
	bits for temporal layer) mapped to the generic LID and TID fields.		bits for temporal layer) mapped to the generic LID and TID fields.
	The S, E, I, and D bits MUST match the correspondingly named bits in		The S, E, I, and D bits MUST match the correspondingly named bits in
	Payload Content Scalability Information (PACSI) payload structures.		Payload Content Scalability Information (PACSI) payload structures.
	The I bit MUST be 1 when the NAL unit type is 5, 7, 8, 13, 15, or an		The I bit MUST be 1 when the NAL unit type is 5, 7, 8, 13, 15, or an
	aggregation packet or fragmentation unit encapsulating any of these		aggregation packet or fragmentation unit encapsulating any of these
	types; otherwise, it MUST be 0. These ranges cover intra (IDR)		types; otherwise, it MUST be 0. These ranges cover intra (IDR)
	frames as well as critical parameter sets (SPS/PPS variants).		frames as well as critical parameter sets (SPS/PPS variants).
	The D bit MUST be 1 when the NAL unit header Network Remote		The D bit MUST be 1 if either:
	Identification (NRI) field is 0, or an aggregation packet or
	fragmentation unit encapsulating only NAL units with NRI=0;		* the payload's NAL unit header's NRI field is 0, or
	otherwise, it MUST be 0. The NRI=0 condition signals non-reference
	frames.		* the payload is an aggregation packet or fragmentation unit
			encapsulating only NAL units with NRI = 0.
			Otherwise, it MUST be 0.
			The NRI = 0 condition signals non-reference frames.
	The B bit cannot be determined reliably from simple inspection of		The B bit cannot be determined reliably from simple inspection of
	payload headers; therefore, it is determined by implementation-		payload headers; therefore, it is determined by implementation-
	specific means. For example, internal codec interfaces may provide		specific means. For example, internal codec interfaces may provide
	information to set this reliably.		information to set this reliably.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ID=? | L=2 |S|E|I|D|B| TID |0| DID | QID | TL0PICIDX |		| ID=? | L=2 |S|E|I|D|B| TID |0| DID | QID | TL0PICIDX |
	skipping to change at line 472 ¶		skipping to change at line 484 ¶
	the timestamp in the prior RTP sequence number from the same SSRC;		the timestamp in the prior RTP sequence number from the same SSRC;
	otherwise, it MUST be 0.		otherwise, it MUST be 0.
	The E bit MUST match the M bit in the RTP header.		The E bit MUST match the M bit in the RTP header.
	The I bit MUST be 1 when the NAL unit type is 5, 7, or 8, or an		The I bit MUST be 1 when the NAL unit type is 5, 7, or 8, or an
	aggregation packet or fragmentation unit encapsulating any of these		aggregation packet or fragmentation unit encapsulating any of these
	types; otherwise, it MUST be 0. These ranges cover intra (IDR)		types; otherwise, it MUST be 0. These ranges cover intra (IDR)
	frames as well as critical parameter sets (SPS/PPS).		frames as well as critical parameter sets (SPS/PPS).
	The D bit MUST be 1 when the NAL unit header NRI field is 0, or an		The D bit MUST be 1 if either:
	aggregation packet or fragmentation unit encapsulating only NAL units
	with NRI=0; otherwise, it MUST be 0. The NRI=0 condition signals		* the payload's NAL unit header's NRI field is 0, or
	non-reference frames.
			* the payload is an aggregation packet or fragmentation unit
			encapsulating only NAL units with NRI = 0.
			Otherwise, it MUST be 0.
			The NRI = 0 condition signals non-reference frames.
	The B bit cannot be determined reliably from simple inspection of		The B bit cannot be determined reliably from simple inspection of
	payload headers; therefore, it is determined by implementation-		payload headers; therefore, it is determined by implementation-
	specific means. For example, internal codec interfaces may provide		specific means. For example, internal codec interfaces may provide
	information to set this reliably.		information to set this reliably.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0|0|0|0| TL0PICIDX |		| ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0|0|0|0| TL0PICIDX |
	skipping to change at line 503 ¶		skipping to change at line 521 ¶
	The S bit MUST match the correspondingly named bit in the VP8 payload		The S bit MUST match the correspondingly named bit in the VP8 payload
	descriptor when PID=0; otherwise, it MUST be 0.		descriptor when PID=0; otherwise, it MUST be 0.
	The E bit MUST match the M bit in the RTP header.		The E bit MUST match the M bit in the RTP header.
	The I bit MUST match the inverse of the P bit in the VP8 payload		The I bit MUST match the inverse of the P bit in the VP8 payload
	header.		header.
	The D bit MUST match the N bit in the VP8 payload descriptor.		The D bit MUST match the N bit in the VP8 payload descriptor.
	The B bit MUST match the Y bit in the VP8 payload descriptor. Note:		The B bit MUST match the Y bit in the VP8 payload descriptor.
	when using temporally nested scalability structures as recommended in
	Section 3.5.2, the B bit and VP8 Y bit will always be 1 if the TID is		| Note: when using temporally nested scalability structures as
	not 0 since it is always possible to switch up to a higher temporal		| recommended in Section 3.5.2, the B bit and VP8 Y bit will
	layer in such nested structures.		| always be 1 if the TID is not 0 since it is always possible to
			| switch up to a higher temporal layer in such nested structures.
	The TID and TL0PICIDX MUST match the correspondingly named fields in		The TID and TL0PICIDX MUST match the correspondingly named fields in
	the VP8 payload descriptor.		the VP8 payload descriptor.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0|0|0|0| TL0PICIDX |		| ID=? | L=2 |S|E|I|D|B| TID |0|0|0|0|0|0|0|0| TL0PICIDX |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	skipping to change at line 539 ¶		skipping to change at line 558 ¶
	An example attribute line in SDP:		An example attribute line in SDP:
	a=extmap:3 urn:ietf:params:rtp-hdrext:framemarking		a=extmap:3 urn:ietf:params:rtp-hdrext:framemarking
	3.5. Usage Considerations		3.5. Usage Considerations
	The header extension values MUST represent what is already in the RTP		The header extension values MUST represent what is already in the RTP
	payload.		payload.
	When an RTP switch needs to discard a received video frame due to		When an RTP switch needs to discard received video frames due to
	congestion control considerations, it is RECOMMENDED that it		congestion control considerations, it is RECOMMENDED that it drop:
	preferably drop frames marked with the D (Discardable) bit set, or
	the highest values of TID and LID, which indicate the highest		* frames marked with the D bit set, or
	temporal and spatial/quality enhancement layers, since those
	typically have fewer dependencies on them than lower layers.		* frames with the highest values of TID and LID (which indicate the
			highest temporal and spatial/quality enhancement layers) since
			those typically have fewer dependencies on them than lower layers.
	When an RTP switch wants to forward a new video stream to a receiver,		When an RTP switch wants to forward a new video stream to a receiver,
	it is RECOMMENDED to select the new video stream from the first		it is RECOMMENDED to select the new video stream from the first
	switching point with the I (Independent) bit set in all spatial		switching point with the I bit set in all spatial layers and forward
	layers and forward the same. An RTP switch can request that a media		the video stream from that point on. An RTP switch can request that
	source generate a switching point by sending Full Intra Request (RTCP		a media source generate a switching point by sending an RTCP Full
	FIR) as defined in [RFC5104], for example.		Intra Request (FIR) as defined in [RFC5104], for example.
	3.5.1. Relation to Layer Refresh Request (LRR)		3.5.1. Relation to Layer Refresh Request (LRR)
	Receivers can use the Layer Refresh Request (LRR) [RFC9627] RTCP		Receivers can use the Layer Refresh Request (LRR) [RFC9627] RTCP
	feedback message to upgrade to a higher layer in scalable encodings.		feedback message to upgrade to a higher layer in scalable encodings.
	The TID/LID values and formats used in LRR messages MUST correspond		The TID/LID values and formats used in LRR messages MUST correspond
	to the same values and formats specified in Section 3.1.		to the same values and formats specified in Section 3.1.
	Because frame marking can only be used with temporally nested		Because frame marking can only be used with temporally nested
	streams, temporal-layer LRR refreshes are unnecessary for frame-		streams, temporal-layer refreshes requested with an LRR message are
	marked streams. Other refreshes can be detected based on the I bit		unnecessary for frame-marked streams. Other refreshes can be
	being set for the specific spatial layers.		detected based on the I bit being set for the specific spatial
			layers.
	3.5.2. Scalability Structures		3.5.2. Scalability Structures
	The LID and TID information is most useful for fixed scalability		The LID and TID information is most useful for fixed scalability
	structures, such as nested hierarchical temporal layering structures,		structures, such as nested hierarchical temporal layering structures,
	where each temporal layer only references lower temporal layers or		where each temporal layer only references lower temporal layers or
	the base temporal layer. The LID and TID information is less useful,		the base temporal layer. The LID and TID information is less useful,
	or even not useful at all, for complex, irregular scalability		or even not useful at all, for complex, irregular scalability
	structures that do not conform to common, fixed patterns of inter-		structures that do not conform to common, fixed patterns of inter-
	layer dependencies and referencing structures. Therefore, it is		layer dependencies and referencing structures. Therefore, it is
	skipping to change at line 640 ¶		skipping to change at line 662 ¶
	6. References		6. References
	6.1. Normative References		6.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[RFC8285] Singer, D., Desineni, H., and R. Even, Ed., "A General
	Mechanism for RTP Header Extensions", RFC 8285,
	DOI 10.17487/RFC8285, October 2017,
	<https://www.rfc-editor.org/info/rfc8285>.
	[RFC6184] Wang, Y.-K., Even, R., Kristensen, T., and R. Jesup, "RTP		[RFC6184] Wang, Y.-K., Even, R., Kristensen, T., and R. Jesup, "RTP
	Payload Format for H.264 Video", RFC 6184,		Payload Format for H.264 Video", RFC 6184,
	DOI 10.17487/RFC6184, May 2011,		DOI 10.17487/RFC6184, May 2011,
	<https://www.rfc-editor.org/info/rfc6184>.		<https://www.rfc-editor.org/info/rfc6184>.
	[RFC6190] Wenger, S., Wang, Y.-K., Schierl, T., and A.		[RFC6190] Wenger, S., Wang, Y.-K., Schierl, T., and A.
	Eleftheriadis, "RTP Payload Format for Scalable Video		Eleftheriadis, "RTP Payload Format for Scalable Video
	Coding", RFC 6190, DOI 10.17487/RFC6190, May 2011,		Coding", RFC 6190, DOI 10.17487/RFC6190, May 2011,
	<https://www.rfc-editor.org/info/rfc6190>.		<https://www.rfc-editor.org/info/rfc6190>.
	[RFC7741] Westin, P., Lundin, H., Glover, M., Uberti, J., and F.		[RFC7741] Westin, P., Lundin, H., Glover, M., Uberti, J., and F.
	Galligan, "RTP Payload Format for VP8 Video", RFC 7741,		Galligan, "RTP Payload Format for VP8 Video", RFC 7741,
	DOI 10.17487/RFC7741, March 2016,		DOI 10.17487/RFC7741, March 2016,
	<https://www.rfc-editor.org/info/rfc7741>.		<https://www.rfc-editor.org/info/rfc7741>.
	[RFC7798] Wang, Y.-K., Sanchez, Y., Schierl, T., Wenger, S., and M.		[RFC7798] Wang, Y.-K., Sanchez, Y., Schierl, T., Wenger, S., and M.
	M. Hannuksela, "RTP Payload Format for High Efficiency		M. Hannuksela, "RTP Payload Format for High Efficiency
	Video Coding (HEVC)", RFC 7798, DOI 10.17487/RFC7798,		Video Coding (HEVC)", RFC 7798, DOI 10.17487/RFC7798,
	March 2016, <https://www.rfc-editor.org/info/rfc7798>.		March 2016, <https://www.rfc-editor.org/info/rfc7798>.
	6.2. Informative References		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
			2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	[RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms
	for Real-Time Transport Protocol (RTP) Sources", RFC 7656,
	DOI 10.17487/RFC7656, November 2015,
	<https://www.rfc-editor.org/info/rfc7656>.
	[RFC7667] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 7667,		[RFC8285] Singer, D., Desineni, H., and R. Even, Ed., "A General
	DOI 10.17487/RFC7667, November 2015,		Mechanism for RTP Header Extensions", RFC 8285,
	<https://www.rfc-editor.org/info/rfc7667>.		DOI 10.17487/RFC8285, October 2017,
			<https://www.rfc-editor.org/info/rfc8285>.
	[RFC6464] Lennox, J., Ed., Ivov, E., and E. Marocco, "A Real-time		6.2. Informative References
	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>.
	[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.		[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
	Jacobson, "RTP: A Transport Protocol for Real-Time		Jacobson, "RTP: A Transport Protocol for Real-Time
	Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,		Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
	July 2003, <https://www.rfc-editor.org/info/rfc3550>.		July 2003, <https://www.rfc-editor.org/info/rfc3550>.
	[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.		[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
	Norrman, "The Secure Real-time Transport Protocol (SRTP)",		Norrman, "The Secure Real-time Transport Protocol (SRTP)",
	RFC 3711, DOI 10.17487/RFC3711, March 2004,		RFC 3711, DOI 10.17487/RFC3711, March 2004,
	<https://www.rfc-editor.org/info/rfc3711>.		<https://www.rfc-editor.org/info/rfc3711>.
	[RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,		[RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
	"Codec Control Messages in the RTP Audio-Visual Profile		"Codec Control Messages in the RTP Audio-Visual Profile
	with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104,		with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104,
	February 2008, <https://www.rfc-editor.org/info/rfc5104>.		February 2008, <https://www.rfc-editor.org/info/rfc5104>.
			[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>.
			[RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and
			B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms
			for Real-Time Transport Protocol (RTP) Sources", RFC 7656,
			DOI 10.17487/RFC7656, November 2015,
			<https://www.rfc-editor.org/info/rfc7656>.
			[RFC7667] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 7667,
			DOI 10.17487/RFC7667, November 2015,
			<https://www.rfc-editor.org/info/rfc7667>.
	[RFC8871] Jones, P., Benham, D., and C. Groves, "A Solution		[RFC8871] Jones, P., Benham, D., and C. Groves, "A Solution
	Framework for Private Media in Privacy-Enhanced RTP		Framework for Private Media in Privacy-Enhanced RTP
	Conferencing (PERC)", RFC 8871, DOI 10.17487/RFC8871,		Conferencing (PERC)", RFC 8871, DOI 10.17487/RFC8871,
	January 2021, <https://www.rfc-editor.org/info/rfc8871>.		January 2021, <https://www.rfc-editor.org/info/rfc8871>.
	[RFC9335] Uberti, J., Jennings, C., and S. Murillo, "Completely		[RFC9335] Uberti, J., Jennings, C., and S. Murillo, "Completely
	Encrypting RTP Header Extensions and Contributing		Encrypting RTP Header Extensions and Contributing
	Sources", RFC 9335, DOI 10.17487/RFC9335, January 2023,		Sources", RFC 9335, DOI 10.17487/RFC9335, January 2023,
	<https://www.rfc-editor.org/info/rfc9335>.		<https://www.rfc-editor.org/info/rfc9335>.
	[RFC9627] Lennox, J., Hong, D., Uberti, J., Holmer, S., and M.		[RFC9627] 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 9627, DOI 10.17487/RFC9627, August 2024,		Message", RFC 9627, DOI 10.17487/RFC9627, February 2025,
	<https://www.rfc-editor.org/info/rfc9627>.		<https://www.rfc-editor.org/info/rfc9627>.
	[RFC9628] Uberti, J., Holmer, S., Flodman, M., Hong, D., and J.		[RFC9628] Uberti, J., Holmer, S., Flodman, M., Hong, D., and J.
	Lennox, "RTP Payload Format for VP9 Video", RFC 9628,		Lennox, "RTP Payload Format for VP9 Video", RFC 9628,
	DOI 10.17487/RFC9628, August 2024,		DOI 10.17487/RFC9628, February 2025,
	<https://www.rfc-editor.org/info/rfc9628>.		<https://www.rfc-editor.org/info/rfc9628>.
	Acknowledgements		Acknowledgements
	Many thanks to Bernard Aboba, Jonathan Lennox, Stephan Wenger, Dale		Many thanks to Bernard Aboba, Jonathan Lennox, Stephan Wenger, Dale
	Worley, and Magnus Westerlund for their inputs.		Worley, and Magnus Westerlund for their inputs.
	Authors' Addresses		Authors' Addresses
	Mo Zanaty		Mo Zanaty
End of changes. 33 change blocks.
	90 lines changed or deleted		112 lines changed or added
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