Network Working Group S. Wenger
Internet Draft Y.-K. Wang
Document: draft-ietf-avt-rtp-svc-00.txt T. Schierl
Expires: June 2007
December 2006
RTP Payload Format for SVC Video
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INTERNET-DRAFT RTP Payload Format for SVC Video December 2006
Abstract
This memo describes an RTP Payload format for the scalable extension
of the ITU-T Recommendation H.264 video codec which is technically
identical to ISO/IEC International Standard 14496-10 video codec.
The RTP payload format allows for packetization of one or more
Network Abstraction Layer Units (NAL units), produced by the video
encoder, in each RTP payload. The payload format has wide
applicability, as it supports applications from simple low bit-rate
conversational, through Internet video streaming with interleaved
transmission, to high bit-rate video-on-demand.
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Table of Content
RTP Payload Format for SVC Video...................................1
1. Introduction.................................................5
1.1. SVC -- the scalable extension of H.264/AVC..................5
2. Conventions..................................................5
3. The SVC Codec................................................6
3.1. Overview....................................................6
3.2. Parameter Set Concept.......................................7
3.3. Network Abstraction Layer Unit Header.......................8
4. Scope.......................................................12
5. Definitions and Abbreviations...............................12
5.1. Definitions................................................12
5.1.1. Definitions per SVC specification........................12
5.1.2. Definitions local to this memo...........................14
5.2. Abbreviations..............................................14
6. RTP Payload Format..........................................15
6.1. Design Principles..........................................15
6.2. RTP Header Usage...........................................16
6.3. Common Structure of the RTP Payload Format.................16
6.4. NAL Unit Header Usage......................................16
6.5. Packetization Modes........................................17
6.6. Decoding Order Number (DON)................................18
6.7. Single NAL Unit Packet.....................................18
6.8. Aggregation Packets........................................18
6.9. Fragmentation Units (FUs)..................................18
6.10. Payload Content Scalability Information (PACSI) NAL Unit...19
7. Packetization Rules.........................................21
8. De-Packetization Process (Informative)......................22
9. Payload Format Parameters...................................22
9.1. MIME Registration..........................................22
9.2. SDP Parameters.............................................24
9.2.1. Mapping of MIME Parameters to SDP........................25
9.2.2. Usage with the SDP Offer/Answer Model....................25
9.2.3. Usage with Session and SSRC multiplexing.................25
9.2.4. Usage in Declarative Session Descriptions................25
9.3. Examples...................................................25
9.4. Parameter Set Considerations...............................25
10. Security Considerations.....................................26
11. Congestion Control..........................................26
12. IANA Consideration..........................................27
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13. Informative Appendix: Application Examples..................27
13.1. Introduction...............................................27
13.2. Layered Multicast..........................................28
13.3. Streaming of an SVC scalable stream........................28
13.4. Multicast to MANE, SVC scalable stream to endpoint.........29
13.5. Scenarios currently not considered for complexity reasons..31
13.6. Scenarios currently not considered for being unaligned with
IP philosophy.....................................................31
13.7. SSRC Multiplexing..........................................33
14. Acknowledgements............................................34
15. References..................................................34
15.1. Normative References.......................................34
15.2. Informative References.....................................35
16. Author's Addresses..........................................35
17. Intellectual Property Statement.............................36
18. Disclaimer of Validity......................................37
19. Copyright Statement.........................................37
20. RFC Editor Considerations...................................37
21. Open Issues.................................................37
22. Changes Log.................................................37
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1. Introduction
1.1. SVC -- the scalable extension of H.264/AVC
This memo specifies an RTP [RFC3550] payload format for a
forthcoming new mode of the H.264/AVC video codec, known as Scalable
Video Coding (SVC). Formally, SVC will take the form of an Amendment
to ISO/IEC 14496 Part 10 [MPEG4-10], and likely as one or more new
Annexes of ITU-T Rec. H.264 [H.264]. It is planned to keep the
technical alignment between the two mentioned specifications, as
well as backward compatibility with previous versions of H.264/AVC.
The current working draft of SVC is available for public review
[SVC]. In this memo, SVC is used as an acronym for the mentioned
scalable extension of H.264/AVC. In that, SVC is a superset of
H.264/AVC.
SVC covers the whole application ranges of H.264/AVC. This range is
considerable, starting with low bit-rate Internet streaming
applications to HDTV broadcast and Digital Cinema with nearly
lossless coding and requiring dozens or hundreds of MBit/s.
This memo tries to follow a backward compatible enhancement
philosophy similar to what the video coding standardization
committees implement, by keeping as close an alignment to the
H.264/AVC payload RFC [RFC3984] as possible. It documents the
enhancements relevant from an RTP transport viewpoint, defines
signaling support for SVC, and deprecates the single NAL unit
packetization mode of RFC 3984.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
This specification uses the notion of setting and clearing a bit
when bit fields are handled. Setting a bit is the same as assigning
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that bit the value of 1 (On). Clearing a bit is the same as
assigning that bit the value of 0 (Off).
3. The SVC Codec
3.1. Overview
SVC provides scalable video bitstreams. In SVC, a scalable video
bitstream contains a base layer conforming to the existing profiles
of H.264 as defined in [H.264], and one or more enhancement layers.
An enhancement layer may enhance the temporal resolution (i.e. the
frame rate), the spatial resolution, or the quality of the video
content represented by the lower layer or part thereof.
Each RTP packet stream can carry NAL units belonging to one or more
layers. The NAL unit headers include information of the association
of a given NAL unit to a layer. Therefore, extracting individual
layers from an RTP packet stream containing more than one layer is a
lightweight operation, involving only fixed length bit fields in the
header as documented in this memo and in [SVC].
Multiple RTP packet streams, regardless whether they carry a single
or multiple layers as discussed above, can be used to transport the
whole scalable bitstream, or operation points thereof. When
multiple RTP packet streams are in use, they are session
multiplexed, i.e. form their own RTP session and therefore have
their own SSRC, PT, and Sequence numbering space, among all other
properties of a session as spelled out in section xxx of [RFC3550].
The concept of video coding layer (VCL) and network abstraction
layer (NAL) is inherited from H.264. The VCL contains the signal
processing functionality of the codec; mechanisms such as transform,
quantization, motion-compensated prediction, loop filtering and
inter-layer prediction. A coded picture in H.264 consists of one or
more slices. In SVC, a particular layer consists of all the coded
slices required for decoding up to that layer. Within one access
unit, a coded picture representing a particular layer consists of
all the coded slices required for decoding up to the particular
layer at the time instance corresponding to the access unit. The
Network Abstraction Layer (NAL) encapsulates each slice generated by
the VCL into one or more Network Abstraction Layer Units (NAL
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units). Please consult RFC 3984 for a more in-depth discussion of
the NAL unit concept. SVC specifies the decoding order of the NAL
units.
``Layer'' in the terms ``Video Coding Layer'' and ``Network
Abstraction Layer'' refers to a conceptual distinction, and is
closely related to syntax layers (block, macroblock, slice, ...
layers). ``Layer'' here describes a syntax level of the bitstream in
contrast to a part of the layered bitstream, which may be discarded.
It should not be confused with base and enhancement layers.
The concept of temporal scalability is not newly introduced by SVC,
as H.264 already supports it. In [H.264], sub-sequences have been
introduced in order to allow optional use of temporal layers. SVC
extends this approach by advertising the temporal layer information
within the NAL unit header, or suffix NAL units, as discussed in
section 3.3 of this memo and in [SVC]. By our definition, the base
layer may be scalable in the temporal dimension.
The concept of scaling the visual content quality in the granularity
of complete enhancement layers, i.e. through omitting the transport
and decoding of entire enhancement layers, is denoted as coarse-
grained scalability (CGS). This is what is commonly understood as
scalability in the IETF community. According to SVC, a CGS layer
may be a spatial or quality (SNR) enhancement layer.
In some cases, the bit rate of a given enhancement layer may be
reduced by truncating bits from individual NAL units. Truncation
leads to a graceful degradation of the video quality of the
reproduced enhancement layer. This concept is known as Fine
Granularity Scalability (FGS). In SVC, FGS is provided by a concept
known as progressive refinement slices.
3.2. Parameter Set Concept
The parameter set concept is inherited from [H.264]. Please refer to
section 1.2 of RFC 3984 for more details.
In SVC, pictures from different layers may use the same sequence or
picture parameter set, but may also use different sequence or
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picture parameter sets. If different sequence or picture parameter
sets are used, then, at any time instant during the decoding
process, there may be more than one active sequence or picture
parameter set. Any specific active sequence parameter set remains
unchanged throughout a coded video sequence in the layer in which
the active sequence parameter set is referred to. The active
picture parameter set remains unchanged within a coded picture.
3.3. Network Abstraction Layer Unit Header
An SVC NAL unit, i.e., a NAL units of type 20 and 21, consists of a
header of four or five bytes and the payload byte string. An SVC
NAL unit typically encapsulates VCL data as defined in Annex G of
[SVC] but may also contain VCL data compliant to older profiles of
[H.264]. A special type of an SVC NAL unit is the suffix NAL unit
that includes descriptive information of a preceding NAL unit.
SVC extends the NAL unit header defined in [H.264] by three or four
additional bytes. The header indicates the type of the NAL unit,
the (potential) presence of bit errors or syntax violations in the
NAL unit payload, information regarding the relative importance of
the NAL unit for the decoding process, the layer decoding dependency
information, and FGS fragmentation information. This RTP payload
specification is designed to be unaware of the bit string in the NAL
unit payload.
The NAL unit header co-serves as the payload header of this RTP
payload format. The payload of a NAL unit follows immediately.
The syntax and semantics of the NAL unit header are formally
specified in [SVC], but the essential properties of the NAL unit
header are summarized below.
The first byte of the NAL unit header has the following format (the
bit fields are the same as in [H.264] and [RFC3984], while the
semantics have changed slightly, in a backward compatible way):
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+---------------+
|0|1|2|3|4|5|6|7|
+-+-+-+-+-+-+-+-+
|F|NRI| Type |
+---------------+
F: 1 bit
forbidden_zero_bit. H.264 declares a value of 1 as a syntax
violation.
NRI: 2 bits
nal_ref_idc. A value of 00 indicates that the content of the NAL
unit is not used to reconstruct reference pictures for inter picture
prediction. Such NAL units can be discarded without risking the
integrity of the reference pictures in the same layer. Values
greater than 00 indicate that the decoding of the NAL unit is
required to maintain the integrity of the reference pictures.
Type: 5 bits
nal_unit_type. This component specifies the NAL unit payload type
as defined in table 7-1 of [SVC], and later within this memo. For a
reference of all currently defined NAL unit types and their
semantics, please refer to section 7.4.1 in [SVC].
Previously, NAL unit types 20 and 21 (among others) have been
reserved for future extensions. SVC is using these two NAL unit
types. They indicate the presence of three or four additional bytes
in the NAL unit header. The first three additional bytes are as
shown below.
+---------------+---------------+---------------+
|0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7|0|1|2|3|4|5|6|7|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|RR | PRID | TL | DID | QL|B|U|D|G|L| O |E|
+---------------+---------------+---------------+
RR: 2 bits
reserved_zero_two_bits. Reserved bits for future extension. RR
MUST be zero.
PRID: 6 bits
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priority_id. This component specifies a priority identifier for the
NAL unit. A lower value of PRID indicates a higher priority.
TL: 3 bits
temporal_id. This component indicates the temporal layer (or frame
rate) hierarchy. Informally put, a layer consisted of pictures of a
smaller temporal_id value has a smaller frame rate. A given
temporal layer typically depends on the lower temporal layers (i.e.
the temporal layers with smaller temporal_id values) but never
depends on any higher temporal layer.
DID: 3 bits
dependency_id. This component denotes the inter-layer coding
dependency hierarchy. At any temporal location, a picture of a
smaller dependency_id value may be used for inter-layer prediction
for coding of a picture of a larger dependency_id value, while a
picture of a larger dependency_id value is disallowed to be used for
inter-layer prediction for coding of a picture of a smaller
dependency_id value.
QL: 2 bits
quality_id. This component designates the quality level hierarchy of
a progressive refinement (PR) or quality (SNR) enhancement layer
slice. At any temporal location and with identical dependency_id
value, a picture with quality_id equal to ql uses a picture with
quality_id equal to ql-1 for inter-layer prediction.
B: 1 bit
layer_base_flag. A value of 1 indicates that no inter-layer
prediction (of coding mode, motion, sample value, and/or residual
prediction) is used for the current slice. A value of 0 indicates
that inter-layer prediction may be used for the current slice.
U: 1 bit
use_base_prediction_flag. A value of 1 indicates that only the base
representations of the reference pictures are used during the inter
prediction process of the current slice. A value of 0 indicates that
the base representations of the reference pictures are not used
during the inter prediction process of the current slice.
D: 1 bit
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discardable_flag. A value of 1 indicates that the content of the
NAL unit with dependency_id equal to currDependencyId is not used in
the decoding process of NAL units with dependency_id larger than
currDependencyId. Such NAL units can be discarded without risking
the integrity of higher scalable layers with larger values of
dependency_id. discardable_flag equal to 0 indicates that the
decoding of the NAL unit is required to maintain the integrity of
higher scalable layers with larger values of dependency_id.
G: 1 bit
fragmented_flag. A value of 1 indicates that the current NAL unit is
a FGS (progressive refinement) slice. A value of 0 indicates that
the current NAL unit is not a FGS slice. If quality_id is equal to
0, fragmented_flag shall be equal to 0.
L: 1 bit
last_fragment_flag. When fragmented_flag is equal to 0, the
semantics of this component is unspecified. When fragmented_flag is
equal to 1, this component, together with fragment_order, specifies
whether the current NAL unit is a fragmented FGS slice, and if yes,
whether the current NAL unit is the last fragment of the fragmented
slice, as follows. When fragment_order is equal to 0 and
last_fragment_flag is equal to 1, the current NAL unit is an un-
fragmented FGS slice. When fragment_order is greater than 0 and
last_fragment_flag is equal to 1, the current NAL unit is the last
fragment of a fragmented FGS slice. When last_fragment_flag is equal
to 0, the current NAL unit is a fragment but not the last fragment
of a fragmented FGS slice.
O: 2 bits
fragment_order. When fragmented_flag is equal to 0, the semantics of
this component is unspecified. When fragmented_flag is equal to 1,
this component, together with last_fragment_flag, specifies whether
the current NAL unit is a fragmented FGS slice, and if yes, the
fragment order, as follows. When fragment_order is equal to 0 and
last_fragment_flag is equal to 1, the current NAL unit is an un-
fragmented FGS slice. When fragment_order is greater than 0 and
last_fragment_flag is equal to 1, the current NAL unit is the last
fragment of a fragmented FGS slice, and fragment_order indicates the
fragment order. When last_fragment_flag is equal to 0, the current
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NAL unit is a fragment but not the last fragment of a fragmented FGS
slice, and fragment_order indicates the fragment order.
E: 1 bit
extension_flag. A value of 1 indicates the existence of the last
byte, tl0_frame_idx, in the NAL unit header. A value of 0 indicates
that tl0_frame_idx is not present in the NAL unit header. Please
refer to [SVC] for information in detail about tl0_frame_idx.
This memo introduces the same additional NAL unit types as RFC 3984,
which are presented in section 6.3. The NAL unit types defined in
this memo are marked as unspecified in [SVC]. Moreover, this
specification extends the semantics of F, NRI, PRID, D, TL, DID and
QL as described in section 6.4.
4. Scope
This payload specification can only be used to carry the "naked" NAL
unit stream over RTP, and not the byte stream format according to
Annex B of [SVC]. Likely, the applications of this specification
will be in the IP based multimedia communications fields including
conversational multimedia, video telephony or video conferencing,
Internet streaming and TV over IP.
This specification allows, in a given RTP session, to encapsulate
NAL units belonging to
o the base layer only, detailed specification in [RFC3984], or
o one or more enhancement layers, or
o the base layer and one or more enhancement layers
5. Definitions and Abbreviations
5.1. Definitions
5.1.1. Definitions per SVC specification
This document uses the definitions of [SVC]. The following terms,
defined in [SVC], are summed up for convenience:
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scalable bitstream: A bitstream that uses the scalable extensions
defined in Annex G of [SVC], i.e. a bitstream with a base layer and
at least one enhancement layer.
suffix NAL unit: A NAL unit that immediately follows another NAL
unit in decoding order and contains descriptive information of the
preceding NAL unit, which is referred to as the associated NAL unit.
A suffix NAL unit shall have nal_ref_idc equal to 20 or 21, shall
have dependency_id and quality_level both equal to 0, and shall not
contain a coded slice. A suffix NAL unit belongs to the same coded
picture as the associated NAL unit. A suffix NAL unit may be used
for indicating temporal levels within the base layer.
base layer: The base layer is typically representing the minimal
spatial resolution and the minimal fidelity of an SVC bitstream.
The base layer must be fully complying with [H.264]. The base layer
is independently decodable without the requirement of using any
other layer of the SVC bitstream. In SVC context each slice NAL
unit in the base layer is associated with a suffix NAL unit, which
has a four or five bytes NAL unit header containing all the syntax
elements described in section 3.3. The base layer may be temporally
scalable.
enhancement layer: An SVC enhancement layer is identified by
priority_id, temporal_level, dependency_id, and quality_level as
defined in [SVC] and summarized in section 3.3.
access unit: A set of NAL units pertaining to a certain temporal
location. An access unit includes the coded slices of all the
scalable layers at that temporal location and possibly other
associated data, e.g. SEI messages and parameter sets.
coded video sequence: A sequence of access units that consists, in
decoding order, of an instantaneous decoding refresh (IDR) access
unit followed by zero or more non-IDR access units including all
subsequent access units up to but not including any subsequent IDR
access unit.
IDR access unit: An access unit in which all the primary coded
pictures are IDR pictures. Such an access unit allows for random
access to any operation point.
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IDR picture: A coded picture with the property that the decoding of
this coded picture and all the following coded pictures in decoding
order, with the same value of dependency_id, can be performed
without inter prediction from any picture prior to the coded picture
in decoding order with the same value of dependency_id. Thus an IDR
picture allows for random access to the scalable layer, which it
belongs to. An IDR picture causes a "reset" in the decoding process
of the scalable layer containing the IDR picture.
progressive refinement (PR) slice: A progressive refinement slice
is contained in an SVC NAL unit that may be truncated since the end
of the slice header for bit-rate and quality reduction. PR slices
provide Fine Granularity Scalability (FGS).
5.1.2. Definitions local to this memo
operation point: An operation point of a SVC bitstream represents a
certain level of temporal, spatial and quality scalability. An
operation point contains all NAL units required for restoring a
valid bitstream (conforming to [SVC]) up to a certain SVC layer.
The operation point is further described by priority_id,
temporal_level, dependency_id, and quality_level values of that
layer.
RTP packet stream: A sequence of RTP packets with increasing
sequence numbers, identical PT and SSRC, carried in one RTP session.
Within the scope of this memo, one RTP packet stream is utilized to
transport an integer number of SVC layers.
Session multiplexing: The scalable SVC bitstream is distributed
onto different RTP sessions, whereby each RTP session carries a
single RTP packet stream. Each RTP session requires a separate
signaling and has a separate Timestamp, Sequence Number, and SSRC
space. Dependency between sessions MUST be signaled according to
[SDPsiglay] and this memo.
5.2. Abbreviations
In addition to the abbreviations defined in [RFC3984], the following
ones are defined.
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CGS: Coarse Granularity Scalability
FGS: Fine Granularity Scalability
6. RTP Payload Format
6.1. Design Principles
The following design principles have been observed:
o Backward compatibility with RFC 3984 wherever possible.
o As the SVC base layer is H.264/AVC compatible, we assume the base
layer (when transmitted in its own session) to be
encapsulated using RFC 3984. Requiring this has the desirable
side effect that it can be used by RFC 3984 legacy devices.
o MANEs are signaling aware and rely on signaling information.
MANEs have state.
o MANEs can terminate RTP sessions, and create different RTP
sessions
with perhaps modified content. This form of a MANE acts as an RTP
mixer.
o MANEs can also act as RTP translators. The perhaps most likely
use case is media-aware stream thinning. By using the payload
header information identifying layers within an RTP session,
MANEs are able to remove packets from the RTP session while
otherwise keeping the session intact. This implies rewriting
the RTP headers of the outgoing packet stream and rewriting of
RTCP Receiver Reports.
o Packet integrity needs to be preserved end-to-end (whereby
end-to-end can mean endpoint to endpoint but also endpoint to
MANE, if (and only if) the MANE acts as a Mixer).
o In case of layered multicast transmission as motivated in section
13.2, each RTP packet stream in a given session may contain NAL
units belong to one or more SVC layer(s) of the same scalable
bitstream. The layers contained within a RTP session may be
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identified by using payload header structures as defined in this
memo.
6.2. RTP Header Usage
Please see section 5.1 of RFC 3984 [RFC3984]. The following applies
in addition.
When layers of an SVC scalable bitstream are transported in more
than one RTP session, e.g. in layered multicast for which the use
case is given in 13.2, session multiplexing MUST be used only as RTP
multiplexing technique.
6.3. Common Structure of the RTP Payload Format
Please see section 5.2 of RFC 3984 [RFC3984].
6.4. NAL Unit Header Usage
The structure and semantics of the NAL unit header were introduced
in section 3.3. This section specifies the semantics of F, NRI,
PRID, D, TL, DID, QL, B, U, G, L, and O according to this
specification.
The semantics of F specified in section 5.3 of [RFC3984] also
applies herein.
For NRI, for the bitstream that is compliant with [H.264] and
transported using RFC 3984, the semantics specified in section 5.3
of [RFC3984] are applicable, i.e., NRI also indicates the relative
importance of NAL units. In SVC context, only the semantics
specified in [SVC] are applicable, i.e., NRI does not indicate the
relative importance of NAL units.
For PRID, the semantics specified in [SVC] applies. In addition,
MANEs implementing unequal error protection may use this information
to protect NAL units with smaller PRID values better than those with
larger PRID values, for example by including only the more important
NAL units in a FEC protection mechanism. The importance for the
decoding process decreases as the PRID value increases.
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For D, in addition to the semantics specified in [SVC], according to
this memo, MANEs may use this information to protect NAL units with
D equal to 0 better than NAL units with D equal to 1. Furthermore,
based on this information, a MANE or a receiver may determine
whether a given NAL unit is required for successfully decoding a
certain operation point of the SVC bitstream.
For TL, DID and QL, in addition to the semantics specified in [SVC],
according to this memo, values of TL, DID or QL indicate the
relative priority in their respective dimension. A lower value of
TL, DID or QL indicates a higher priority if the other two
components are identical correspondingly. MANEs may use this
information to protect more important NAL units better than less
important NAL units.
Informative note: PRID, D, TL, DID, and QL, in combination,
provide complete information of the relative priority of a NAL
unit compared to any other NAL unit. [Edt. note: examples may be
provided in Informative Appendix 13 in future versions.]
For U, in addition to the semantics specified in [SVC], according to
this memo, MANEs may use this information to protect NAL units with
U equal to 1 (which are referred to as key picture NAL units) better
than NAL units with U equal to 0.
6.5. Packetization Modes
Please see section 5.4 of RFC 3984 [RFC3984]. The single NAL unit
packetization mode SHALL NOT be used.
Informative note: The non-interleaved mode allows an application
to encapsulate a single NAL unit in a single RTP packet.
Historically, the single NAL unit mode has been included into
[RFC3984] only for compatibility with ITU-T Rec. H.241 Annex A
[H.241]. There is no point in carrying this historic ballast
towards a new application space such as the one provided with SVC.
More technically speaking, the implementation complexity increase
for providing the additional mechanisms of the non-interleaved
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mode (namely STAPs) is so minor, and the benefits are so great,
that we require STAP implementation.
6.6. Decoding Order Number (DON)
Please see section 5.5 of RFC 3984 [RFC3984]. The following applies
in addition.
When different layers of a SVC bitstream are transported in more
than one RTP packet stream, the interleaved packetization mode MUST
be used, and the DON values of all the NAL units MUST indicate the
correct NAL unit decoding order over all the RTP packet streams.
If Session multiplexing is used, each session MUST signal an
identical value for the MIME parameters sprop-interleaving-depth,
sprop-max-don-diff, sprop-deint-buf-req, and sprop-init-buf-time.
Further, these values must be valid for the reception capabilities
over all sessions. A receiver MUST signal the same MIME parameter
deint-buf-cap for all sessions used for Session multiplexing.
[Ed.Note(YkW): I think we need more thinking on the value of the
parameters. For example, requiring the parameters be the same for
all the RTP streams and clients might be overkill for receivers of
only lower layers.]
Edt. Note (StW): In RFC3984, the aforementioned codepoints are
optional. It appears that for SVC, when used in conjunction with
session mux, they are mandatory. I don't know how to express this
in the MIME registration; we'll cross that bridge once we are
getting to it.
6.7. Single NAL Unit Packet
Please see section 5.6 of RFC 3984 [RFC3984].
6.8. Aggregation Packets
Please see section 5.7 of RFC 3984 [RFC3984].
6.9. Fragmentation Units (FUs)
Please see section 5.8 of RFC 3984 [RFC3984].
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6.10. Payload Content Scalability Information (PACSI) NAL Unit
A new NAL unit type is specified in this memo, and referred to as
payload content scalability information (PACSI) NAL unit. The PACSI
NAL unit, if present, MUST be the first NAL unit in an aggregation
packet, and it MUST NOT be present in other types of packets. The
PACSI NAL unit indicates scalability characteristics that are common
for all the remaining NAL units in the payload, thus making it
easier for MANEs to decide whether to forward/process/discard the
aggregation packet. Senders MAY create PACSI NAL units and
receivers MAY ignore them, or use them as hints to enable efficient
aggregation packet processing.
Informative note: The NAL unit type for the PACSI NAL unit is
selected among those values that are unspecified in the SVC
specification and in RFC 3984 -- and therefore are ignored by
H.264/AVC or SVC decoders and RFC 3984 receivers. Hence an SVC
stream, even when including PACSI NAL units, can be processed
with RFC 3984 receivers and H.264/AVC or SVC decoders.
When the first aggregation unit of an aggregation packet contains a
PACSI NAL unit, there MUST be at least one additional aggregation
unit present in the same packet. The RTP header fields are set
according to the remaining NAL units in the aggregation packet.
When a PACSI NAL unit is included in a multi-time aggregation
packet, the decoding order number for the PACSI NAL unit MUST be set
to indicate that the PACSI NAL unit is the first NAL unit in
decoding order among the NAL units in the aggregation packet or the
PACSI NAL unit has an identical decoding order number to the first
NAL unit in decoding order among the remaining NAL units in the
aggregation packet.
The structure of PACSI NAL unit is exactly the same as the four-byte
SVC NAL unit header (where E is equal to 0) specified in 3.3, and
reproduced here once more for convenience:
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+---------------+---------------+---------------+---------------+
|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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|NRI| Type |RR | PRID | TL | DID | QL|B|U|D|G|L| O |E|
+---------------+---------------+---------------+---------------+
The values of the fields in PACSI NAL unit MUST be set as follows.
o The F bit MUST be set to 1 if the F bit in at least one remaining
NAL unit in the payload is equal to 1. Otherwise, the F bit MUST
be set to 0.
o The NRI field MUST be set to the highest value of NRI field among
all the remaining NAL units in the payload.
o The Type field MUST be set to 30.
o The RR field MUST be set
to 0.
o The PRID field MUST be set to the lowest value of the PRID values
associated with all the remaining NAL units in the payload.
o The TL field MUST be set to the lowest value of the TL values
associated with all the remaining NAL units in the payload.
o The DID field MUST be set to the lowest value of the DID values
associated with all the remaining NAL units in the payload.
o The QL field MUST be set to the lowest value of the QL values
associated with all the remaining NAL units in the payload.
o The B bit MUST be set to 1 if
the B bit associated with all the remaining NAL units in
the payload is equal to 1. Otherwise, the B bit MUST be set
to 0.
o The U bit MUST be set
to 1 if the U bit associated with all the
remaining NAL units in the payload is equal to 1. Otherwise, the
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U bit
MUST be set to 0.
o The D bit MUST be set to 0 if the D value associated with at least
one remaining NAL unit in the payload is equal to 0. Otherwise,
the D bit MUST be set to 1.
o The G bit MUST be set to 1 if
the G bit associated with at least one of the remaining NAL units
in
the payload is equal to 1. Otherwise, the G bit MUST be set
to 0.
o The L bit MUST be set to 1 if
for any NAL unit having fragmented_flag equal to 1 in the payload,
the corresponding NAL unit having the bit L equal to 1 is also in
the payload. Otherwise, the bit L MUST
be set to 0.
o The O field MUST be set to the
lowest value of the O values associated with all the remaining NAL
units in the payload.
o The E field or extension_flag field (1 bit) MUST be set to 0.
7. Packetization Rules
Please see section 6 of RFC 3984 [RFC3984]. The following rules
apply in addition.
The single NAL unit mode SHALL NOT be used. (See also section 6.5
for the motivation).
When a suffix NAL unit is encapsulated for transmission, it SHOULD
be aggregated to the same transmission packet as the NAL unit
preceding the suffix NAL unit in decoding order.
Informative note: When either the suffix NAL unit or the
associated NAL unit containing an H.264/AVC coded slice is lost,
the remaining one would be of no use in SVC context.
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When layers of a SVC bitstream are transported in more than one RTP
session, the interleaved packetization mode MUST be used.
8. De-Packetization Process (Informative)
Please see section 7 of RFC 3984 [RFC3984]. The following rules
apply in addition.
[Edt. Do we need here more information about cross layer DON? TS:
Yes, in the next version.]
9. Payload Format Parameters
[Edt. note: this section 9 and its subsections will be updated
according to the changes listed below, a little later in the
process. For now, we just list the adjustments necessary, so not to
bury any new information in the RFC 3984 text.]
Section 8 of [RFC3984] applies with the following modification.
The sentence
''The parameters are specified here as part of the MIME subtype
registration for the ITU-T H.264 | ISO/IEC 14496-10 codec.''
is replaced with
''The parameters are specified here as part of the MIME subtype
registration for the SVC codec.''
9.1. MIME Registration
Editor's note: this needs to be updated by copy-pasting the
RFC 3984 MIME registration into this document, so to make it
self-contained. Will be done later in the process.
The MIME subtype for the SVC codec is allocated from the IETF tree.
The receiver MUST ignore any unspecified parameter.
Media Type name: video
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Media subtype name: H.264-SVC
Required parameters: none
OPTIONAL parameters:
The optional MIME parameters specified in [RFC3984] apply, with the
following constraints (to be edited in at the appropriate time):
sprop-interleaving-depth:
In case of using Session multiplexing, the same sprop-interleaving-
depth value MUST be signaled for all sessions and MUST be valid over
all sessions of the multiplex.
sprop-max-don-diff:
In case of using Session multiplexing, the same sprop-max-don-diff
value MUST be signaled for all sessions and MUST be valid over all
sessions of the multiplex.
sprop-deint-buf-req:
In case of using Session multiplexing, the same sprop-deint-buf-req
value MUST be signaled for all sessions and MUST be valid over all
sessions of the multiplex.
sprop-init-buf-time:
In case of using Session multiplexing, the same sprop-init-buf-time
value MUST be signaled for all sessions and MUST be valid over all
sessions of the multiplex.
deint-buf-cap:
In case of using Session multiplexing, the same deint-buf-cap value
MUST be signaled by the receiver for all sessions and MUST be valid
over all sessions of the multiplex.
In addition the following optional MIME parameters apply:
sprop-scalability-info:
This parameter MAY be used to convey the NAL unit containing the
scalability information SEI message as specified in [SVC]. The
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parameter MUST NOT be used to indicate codec capability in any
capability exchange procedure. The value of the parameter is the
base64 representation of the NAL unit containing the scalability
information SEI message.
sprop-layer-ids:
This parameter MAY be used to signal the layer identification
value(s), expressed by the value of the the second and the third
byte of the SVC NAL unit header, for one or more SVC layer(s)
conveyed in one RTP session. A layer identification is a three
character value base64 coded. If more than one layer is transmitted
within one RTP session, the layer identification value of each layer
MUST be itemized with decreasing importance for decoding and MUST be
comma-separated.
Encoding considerations:
This type is only defined for transfer
via RTP (RFC 3550).
Security considerations:
See section 9 of RFC XXXX.
Public specification:
Please refer to section 15 of RFC XXXX.
Additional information:
None
File extensions: none
Macintosh file type code: none
Object identifier or OID: none
Person & email address to contact for further information:
Intended usage: COMMON
Author:
Change controller:
IETF Audio/Video Transport working group
delegated from the IESG.
9.2. SDP Parameters
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9.2.1. Mapping of MIME Parameters to SDP
The MIME media type video/SVC string is mapped to fields in the
Session Description Protocol (SDP) as follows:
* The media name in the "m=" line of SDP MUST be video.
* The encoding name in the "a=rtpmap" line of SDP MUST be SVC (the
MIME subtype).
* The clock rate in the "a=rtpmap" line MUST be 90000.
* The OPTIONAL parameters "profile-level-id", "max-mbps", "max-fs",
"max-cpb", "max-dpb", "max-br", "redundant-pic-cap", "sprop-
parameter-sets", "parameter-add", "packetization-mode", "sprop-
interleaving-depth", "deint-buf-cap", "sprop-deint-buf-req",
"sprop-init-buf-time", "sprop-max-don-diff", "max-rcmd-nalu-
size'', ''sprop-layer-ids'', and ''sprop-scalability-info'', when
present, MUST be included in the "a=fmtp" line of SDP. These
parameters are expressed as a MIME media type string, in the form
of a semicolon separated list of parameter=value pairs.
9.2.2. Usage with the SDP Offer/Answer Model
TBD.
9.2.3. Usage with Session and SSRC multiplexing
If Session multiplexing is used, the rules on signaling media
decoding dependency in SDP as defined in [SDPsiglay] apply.
9.2.4. Usage in Declarative Session Descriptions
TBD.
9.3. Examples
TBD.
9.4. Parameter Set Considerations
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Please see section 10 of RFC 3984 [RFC3984].
10. Security Considerations
Please see section 11 of RFC 3984 [RFC3984].
11. Congestion Control
Within any given RTP session carrying payload according to this
specification, the provisions of section 12 of RFC 3984 [RFC3984]
apply. Reducing the session bandwidth is possible by one or more of
the following means, listed in an order that, in most cases, will
assure the least negative impact to the user experience:
a) removing some or all bits of a given FGS NAL unit as long as the
remaining bits still form a conforming SVC NAL unit. Note: doing
so does not reduce the number of NAL units, but the bit rate of
the highest enhancement layer. This can be translated into a
reduced packet count when aggregating those smaller NAL units
into packets small enough to fit the MTU size.
b) stop sending NAL units belonging to the highest enhancement
layer(s), when more than one layer is transported in the session.
c) dropping NAL units of the base layer according to their
importance for the decoding process, as indicated in the NAL
unit's NRI field (this may lead to a non-compliant bitstream, and
annoying artifacts)
d) dropping NAL units or entire packets not according to the
aforementioned rules (media-unaware stream thinning). This
results in the reception of a non-compliant bitstream and, most
likely, in very annoying artifacts
Informative note: The discussion above is centered on NAL
units and not on packets, primarily because that is the level
where senders can meaningfully manipulate the scalable
bitstream. The mapping of NAL units to RTP packets is fairly
flexible when using aggregation packets. Depending on the
nature of the congestion control algorithm, the ''dimension''
of congestion measurement (packet count or bitrate) and
reaction to it (reducing packet count or bitrate or both) can
be adjusted accordingly.
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When multiple sessions are SSRC multiplexed onto the same transport
address, a receiver can still calculate and communicate in RTCP-RRs
the per-session congestion. However, when it is known that these
SSRC-multiplexed sessions originate from the same sender's transport
address (a condition henceforth referred to as ''on the same path
All aforementioned means are available to the RTP sender, regardless
whether that sender is located in the sending endpoint or in a mixer
based MANE.
When a translator-based MANE is employed, then the MANE MAY
manipulate the session only on the MANE's outgoing path, so that the
sensed end-to-end congestion falls within the permissible envelope.
As all translators, in this case the MANE needs to rewrite RTCP RRs
to reflect the manipulations it has performed on the session.
12. IANA Consideration
[Edt. Note: A new MIME type should be registered from IANA.]
13. Informative Appendix: Application Examples
13.1. Introduction
Scalable video coding is a concept that has been around at least
since MPEG-2 [MPEG2], which goes back as early as 1993.
Nevertheless, it has never gained wide acceptance; perhaps partly
because applications didn't materialize in the form envisioned
during standardization.
MPEG and JVT, respectively, performed a requirement analysis before
the SVC project was launched. Dozens of scenarios have been
studied. While some of the scenarios appear not to follow the most
basic design principles of the Internet -- and are therefore not
appropriate for IETF standardization -- others are clearly in the
scope of IETF work. Of these, this draft chooses the following
subset for immediate consideration. Note that we do not reference
the MPEG and JVT documents directly; partly, because at least the
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MPEG documents have a limited lifespan and are not publicly
available, and partly because the language used in these documents
is inappropriately video centric and imprecise, when it comes to
protocol matters.
With these remarks, we now introduce three main application
scenarios that we consider as relevant, and that are implementable
with this specification.
13.2. Layered Multicast
This well-understood form of the use of layered coding
[McCanne/Vetterli] implies that all layers are individually conveyed
in their own RTP packet streams, each carried in its own RTP session
using the IP (multicast) address and port number as the single
demultiplexing point. Receivers ''tune'' into the layers by
subscribing to the IP multicast, normally by using IGMP [IGMP].
Layered Multicast has the great advantage of simplicity and easy
implementation. However, it has also the great disadvantage of
utilizing many different transport addresses. While we consider
this not to be a major problem for a professionally maintained
content server, receiving client endpoints need to open many ports
to IP multicast addresses in their firewalls. This is a practical
problem from a firewall/NAT viewpoint. Furthermore, even today IP
multicast is not as widely deployed as many wish.
We consider layered multicast an important application scenario for
three reasons. First, it is well understood and the implementation
constraints are well known. There may well be large scale IP
networks outside the immediate Internet context that may wish to
employ layered multicast in the future. One possible example could
be a combination of content creation and core-network distribution
for the various mobile TV services, e.g. those being developed by
3GPP (MBMS) [MBMS] and DVB (DVB-H) [DVB-H].
13.3. Streaming of an SVC scalable stream
In this scenario, a streaming server has a repository of stored SVC
coded layers for a given content. At the time of streaming, and
according to the capabilities, connectivity, and congestion
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situation of the client(s), the streaming server generates and
serves a scalable stream. Both unicast and multicast serving is
possible. At the same time, the streaming server may use the same
repository of stored layers to compose different streams (with a
different set of layers) intended for other audiences.
As every endpoint receives only a single SVC RTP session, the number
of firewall pinholes can be optimized to one.
The main difference between this scenario and straightforward
simulcasting lies in the architecture and the requirements of the
streaming server, and is therefore out of the scope of IETF
standardization. However, compelling arguments can be made why such
a streaming server design makes sense. One possible argument is
related to storage space and channel bandwidth. Another is
bandwidth adaptivity without transcoding -- a considerable advantage
in a congestion controlled network. When the streaming server
learns about congestion, it can reduce sending bitrate by choosing
fewer layers or utilizing FGS, when composing the layered stream;
see section 10. SVC is designed to gracefully support both
bandwidth rampdown and bandwidth rampup with a considerable dynamic
range. This payload format is designed to allow for bandwidth
flexibility in the mentioned sense, both for CGS and FGS layers.
While, in theory, a transcoding step could achieve a similar dynamic
range, the computational demands are impractically high and video
quality is typically lowered -- therefore, few (if any) streaming
servers implement full transcoding.
13.4. Multicast to MANE, SVC scalable stream to endpoint
This scenario is a bit more complex, and designed to optimize the
network traffic in a core network, while still requiring only a
single pinhole in the endpoint's firewall. One of its key
applications is the mobile TV market.
Consider a large private IP network, e.g. the core network of 3GPP.
Streaming servers within this core network can be assumed to be
professionally maintained. We assume that these servers can have
many ports open to the network and that layered multicast is a real
option. Therefore, we assume that the streaming server multicasts
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SVC scalable layers, instead of simulcasting different
representations of the same content at different bit rates.
Also consider many endpoints of different classes. Some of these
endpoints may not have the processing power or the display size to
meaningfully decode all layers; other may have these capabilities.
Users of some endpoints may not wish to pay for high quality and are
happy with a base service, which may be cheaper or even free. Other
users are willing to pay for high quality. Finally, some connected
users may have a bandwidth problem in that they can't receive the
bandwidth they would want to receive -- be it through congestion,
connectivity, change of service quality, or for whatever other
reasons. However, all these users have in common that they don't
want to be exposed too much, and therefore the number of firewall
pinholes need to be small.
This situation can be handled best by introducing middleboxes close
to the edge of the core network, which receive the layered multicast
streams and compose the single SVC scalable bit stream according to
the needs of the endpoint connected. These middleboxes are called
MANEs throughout this specification. In practice, we envision the
MANE to be part of (or at least physically and topologically close
to) the base station of a mobile network, where all the signaling
and media traffic necessarily are multiplexed on the same physical
link. This is why we do not worry too much about decomposition
aspects of the MANE as such.
MANEs necessarily need to be fairly complex devices. They certainly
need to understand the signaling, so, for example, to associate the
PT octet in the RTP header with the SVC payload type.
A MANE may terminate the multicasted layered RTP sessions incoming
from the core network side, and create new RTP sessions (perhaps
even multicast sessions) to the endpoints connected to them. In RTP
terminology, these types of MANEs are RTP mixers. This implies, per
RFC 3550, a very loose relationship between the incoming and
outgoing RTP sessions. In particular, there is no direct
relationship between the incoming and outgoing RTP sequence numbers,
RTP timestamps, payload types used, etc.
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Mixer-based MANEs are conceptually easy to implement and can offer
powerful features, primarily because they necessarily can ''see'' the
payload (including the RTP payload headers), utilize the wealth of
layering information available therein, and manipulate it.
While a mixer-based MANE operation in its most trivial form
(combining multiple RTP packet streams into a single one) can be
implemented comparatively simply -- reordering the incoming packets
according to the DON and sending them in the appropriate order --
more complex forms can also be envisioned. For example, a mixer-
type MANE can be optimizing the outgoing RTP stream to the MTU size
of the outgoing path by utilizing the aggregation and fragmentation
mechanisms of this memo.
A MANE can also act as a translator. In this case, we envision its
functionality to stream thinning, so to adhere to congestion control
principles as discussed in section 11. While the implementation of
the forward (media) channel of such a MANE appears to be
comparatively simple, the need to rewrite RTCP RRs makes even such a
MANE a complex device.
While the implementation complexity of either case of a MANE, as
discussed above, is fairly high, the computational demands are
comparatively low. In particular, SVC and/or this specification
contain means to easily generate the correct inter-layer decoding
order of NAL units. It is also simple to identify the fine
granularity scalable bits in a given NAL unit. No serious bit-
oriented processing is required and no significant state information
(beyond that of the signaling and perhaps the SVC sequence parameter
sets) need to be kept.
13.5. Scenarios currently not considered for complexity reasons
-- vacat --
13.6. Scenarios currently not considered for being unaligned with IP
philosophy
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Remarks have been made that the current draft does not take into
consideration at least one application scenario which some JVT folks
consider important. In particular, their idea is to make the RTP
payload format (or the media stream itself) self-contained enough
that a stateless, non signaling aware device can ''thin'' an RTP
session to meet the bandwidth demands of the endpoint. They call
this device a ''Router'' or ''Gateway'', and sometimes a MANE.
Obviously, it's not a Router or Gateway in the IETF sense. To
distinguish it from a MANE as defined in RFC 3984 and in this
specification, let's call it a MDfH (Magic Device from Heaven).
To simplify discussions, let's assume point-to-point traffic only.
The endpoint has a signaling relationship with the streaming server,
but it is known that the MDfH is somewhere in the media path (e.g.
because the physical network topology ensures this). It has been
requested, at least implicitly through MPEG's and JVT's requirements
document, that the MDfH should be capable to intercept the SVC
scalable bit stream, modify it by dropping packets or parts thereof,
and forwarding the resulting packet stream to the receiving
endpoint. It has been requested that this payload specification
contains protocol elements facilitating such an operation, and the
argument has been made that the NRI field of RFC 3984 serves exactly
the same purpose.
The authors of this I-D do not consider the scenario above to be
aligned with the most basic design philosophies the IETF follows,
and therefore have not addressed the comments made (except through
this section). In particular, we see the following problems with
the MDfH approach):
- As the very minimum, the MDfH would need to know which RTP streams
are carrying SVC. We don't see how this could be accomplished but
by using a static payload type. None of the IETF defined RTP
profiles envision static payload types for SVC, and even the de-
facto profiles developed by some application standard
organizations (3GPP for example) do not use this outdated concept.
Therefore, the MDfH necessarily needs to be at least ''listening''
to the signaling.
- If the RTP packet payload were encrypted, it would be impossible
to interpret the payload header and/or the first bytes of the
media stream. We understand that there are crypto schemes under
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discussion that encrypt only the last n bytes of an RTP payload,
but we are more than unsure that this is fully in line with the
IETF's security vision.
Even if the above two problems would have been overcome through
standardization outside of the IETF, we still foresee serious design
flaws:
- An MDfH can't simply dump RTP packets it doesn't want to forward.
It either needs to act as a full RTP Translator (implying that it
rewrites RTCP RRs and such), or it needs to patch the RTP sequence
numbers to fulfill the RTP specification. Not doing either would,
for the receiver, look like the gaps in the sequence numbers
occurred due to unintentional erasures, which has interesting
effects on congestion control (if implemented), will break pretty
much every meta-payload ever developed, and so on. (Many more
points could be made here).
- An MDfH also can't ''prune'' FGS packets. Again, doing so would
not be compatible with meta payloads, and would mess up RTCP RRs
and congestion control (if the congestion control is based on
octet count and not on packet count; there are discussions related
to the former at least in the context of TFRC).
In summary, based on our current knowledge we are not willing to
specify protocol mechanisms that support an operation point that has
so little in common with classic RTP use.
13.7. SSRC Multiplexing
The authors have complentated the idea of introducing SSRC
multiplexing, i.e. allowing to send multiple RTP packet streams
containing layers in the same RTP session, differentiated by SSRC
values. Our intention was to minimize the number of firewall
pinholes in an endpoint to one, by using MANEs to aggregate multiple
outgoing sessions stemming from a server into a single session (with
SSRC multiplexed packet streams). We were hoping that would be
feasible even with encrypted packets in an SRTP context.
While an implementation along these lines indeed appears to be
feasible for the forward media path, the RTCP RR rewrite cannot be
implemented in the way necessary for this scheme to work. This
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relates to the need to authenticate the RTCP RRs as per SRTP. While
the RTCP RR itself does not need to be rewritten by the scheme we
envisioned, it's transport addresses needs to be manipulated. This,
in turn, is incompatible with the mandatory authetification of RTCP
RRs. As a result, there would be an requirement that a MANE needs
to be in the RTCP security context of the sessions, which was not
envisioned in our use case.
As the envisioned use case cannot be implemented, we refrained to
add the considerable document complexity to support SSRC
multiplexing herein.
14. Acknowledgements
Funding for the RFC Editor function is currently provided by the
Internet Society.
15. References
15.1. Normative References
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[MPEG4-10] ISO/IEC International Standard 14496-10:2003.
[H.264] ITU-T Recommendation H.264, "Advanced video coding for
generic audiovisual services", May 2003.
[SDPsiglay] Schierl, T., ''Signaling media decoding dependency in
Session
Description Protocol (SDP)'', IETF internet draft
draft-schierl-mmusic-layered-codec-02, December 2007.
[SVC] Joint Video Team, ''Joint Scalable Video Model 8: Joint
Draft 8
with proposed changes'', available from http://ftp3.itu.ch
/av-arch/jvt-site /jvt-site/2006_10_Hangzhou/JVT-U202.zip ,
October 2006.
[RFC3984] Wenger, S., Hannuksela, M, Stockhammer, T, Westerlund, M,
Singer, D, ''RTP Payload Format for H.264 Video'', RFC 3984,
February 2005.
Wenger, Wang, Schierl Standards Track [page 34]
INTERNET-DRAFT RTP Payload Format for SVC Video December 2006
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
15.2. Informative References
[DVB-H] DVB - Digital Video Broadcasting (DVB); DVB-H
Implementation Guidelines, ETSI TR 102 377, 2005
[H.241] ITU-T Rec. H.241, ''Extended video procedures and control
signals for
H.300-series terminals'', May 2006
[IGMP] Cain, B., Deering S., Kovenlas, I., Fenner, B. and
Thyagarajan, A., ''Internet Group Management Protocol,
Version 3'', RFC 3376, October 2002.
[McCanne/Vetterli]
V. Jacobson, S. McCanne and M. Vetterli. Receiver-
driven layered multicast. In Proc. of ACM SIGCOMM'96, pages
117--130, Stanford, CA, August 1996.
[MBMS] 3GPP - Technical Specification Group Services and System
Aspects; Multimedia Broadcast/Multicast Service (MBMS);
Protocols and codecs (Release 6), December 2005.
[MPEG2] ISO/IEC International Standard 13818-2:1993.
[SRTP] Baugher, M., McGrew, D, Naslund, M, Carrara, E,
Norrman, K, ''The secure real-time transport protocol
(SRTP)'', RFC 3711, March 2004.
16. Author's Addresses
Stephan Wenger Phone: +358-50-486-0637
Nokia Research Center Email: stewe@stewe.org
P.O. Box 100
FIN-33721 Tampere
Finland
Ye-Kui Wang Phone: +358-50-486-7004
Nokia Research Center Email: ye-kui.wang@nokia.com
P.O. Box 100
FIN-33721 Tampere
Finland
Wenger, Wang, Schierl Standards Track [page 35]
INTERNET-DRAFT RTP Payload Format for SVC Video December 2006
Thomas Schierl Phone: +49-30-31002-227
Fraunhofer HHI Email: schierl@hhi.fhg.de
Einsteinufer 37
D-10587 Berlin
Germany
17. Intellectual Property Statement
Full Copyright Statement
Copyright (C) The IETF Trust (2006).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
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Copies of IPR disclosures made to the IETF Secretariat and any
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http://www.ietf.org/ipr.
Wenger, Wang, Schierl Standards Track [page 36]
INTERNET-DRAFT RTP Payload Format for SVC Video December 2006
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgement
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Further, the author Thomas Schierl of Fraunhofer HHI is sponsored
by the European Commission under the contract number FP6-IST-0028097,
project ASTRALS.
18. RFC Editor Considerations
none
19. Open Issues
1. Packetization rules need work.
3. Alignment with the SVC specification (ongoing)
20. Changes Log
Version 00
- 29.08.2005, YkW: Initial version
- 29.09.2005, Miska: Reviewed and commented throughout the document
- 05.10.2006, StW: Editorial changes through the document, and
formatted the document in RFC payload format style
From -00 to -01
- 04.02.2006, StW: Added details to scope
- 04.02.2006, StW: Added short subsection 6.1 ''Design Principles''
- 04.02.2006, StW: Added section 15, ''Application Examples''
- 06.02 - 03.03.2006, YkW: Various modifications throughout the
document
Wenger, Wang, Schierl Standards Track [page 37]
INTERNET-DRAFT RTP Payload Format for SVC Video December 2006
- 13.02.2006 - 03.03.2006 , ThS: Added definitions and additional
information to section 3.3, 5.1, 7 and 8, parameters in section 9.1 and
added section 14 for NAL unit re-ordering for layered multicast.
Further modifications throughout the document
From -01 to -02
- 06.03.2006, StW: Editorial improvements
- 26.05.2006, YkW: Updated NAL unit header syntax and semantics
according to the latest draft SVC spec
- 20.06.2006, Miska/YkW: Added section 6.10 ''Payload Content
Scalability Information (PACSI) NAL Unit''
- 20.06.2006, YkW: Updated the NAL unit reordering process for layered
multicast (removed the old section 14 ''Informative Appendix: NAL Unit
Re-ordering for Layered Multicast'' and added the new section 13 ''NAL
Unit Reordering for Layered Multicast'')
From -02 to -03
- 05.09.2006, YkW: Updated the NAL unit header syntax, definitions,
etc., according to the foreseen July JVT output. Updated possible MANE
adaptation operations according to SPID, TL, DID and QL. Clarified the
removal of single NAL unit packetiztaion mode. Added the support of
SSRC multiplexing in layered multicast.
- 08.09.2006, StW: Editorial changes throughout the document
- 08.09.2006, YkW: Added the packetization rule for suffix NAL unit.
- 19.09.2006, YkW: Moved/updated SSRC multiplexing support to section
6.2 ``RTP header usage''. Moved/updated the cross layer DON constraint
to Section 6.6 ``Decoding order number''. Moved/updated the
packetization rule when a SVC bistream is transported over more than
one RTP session to Section 7 ``Packetization rules''. Removed Section
13 ''Support of layered multicast''.
- 16.10, TS: Added detailed four-byte NAL unit header description.
Change ''AVC'' to ''H.264'' conforming to 3984. Modifications throughout
the document. Extended description of 3rd byte of PACSI NAL unit.
Corrected terms RTP session and RTP packet stream in case of SSRC
multiplexing. Added terms in definition section on RTP multiplexing.
Constraints on optional MIME parameters of 3984 for cross-layer DON
(DON section and MIME parameters). Copied parts of SI paper regarding
mixer, translator and SSRC mux with SRTP to section application
examples. Added section on SDP usage with Session and SSRC
Wenger, Wang, Schierl Standards Track [page 38]
INTERNET-DRAFT RTP Payload Format for SVC Video December 2006
multiplexing. Added points in Design principles on translator/mixer and
RTP multiplexing. Added additional founding information in Ack-
section. Corrected reference for SVC and added reference for generic
signaling.
17.10, StW: Fixed many editorials, clarified MANE, mixer, translator
and RTP packet stream throughout doc (hopefully consistently)
18.10., removed comments, clarified B-Bit, changed definition of base-
layer (do not need to be of the lowest temporal resolution),
From -03 to draft-ietf-avt-rtp-svc-00
- 23.11.06, StW: Editorials throughout the memo
- 23.11.06, StW: removed all occurrences of the security
discussions, as they are incorrect. When using SRTP, the RTCP is
authenticated, implying that a translator cannot rewrite RTCP RRs,
implying that RRs would be incorrect as soon as the session is
modified (i.e. packets are being removed), implying that SSRC-mux
does not work in multicast.
- 23.11.06, StW: rewrote congestion control
- 23.11.06, StW: removed application scenario related to SRTP, as
this does not work (see above
- 23.11.06, StW: added informative reference to H.241
- 27/29.11.06, YkW: editorial changes throughout the document
- 27/29.11.06, YkW: alignment with the SVC specification
- 19.12.06, TS:
TS: [SVC] is now the complete Joint Draft of H.264
TS: Removed SSRC Multiplexing
TS: Changed use cases for MANE as a translator
TS: Editorials throughout the document, alignment with SVC spec.
- 20-28.12.06, StW/TS/YkW: editorial changes throughout the document
Wenger, Wang, Schierl Standards Track [page 39]
