Audio/Video Transport WG Y.-K. Wang
Internet Draft Nokia
Intended status: Standards track T. Schierl
Expires: February 2009 Fraunhofer HHI
August 21, 2008
RTP Payload Format for MVC Video
draft-wang-avt-rtp-mvc-02.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This memo describes an RTP payload format for the multiview
extension of the ITU-T Recommendation H.264 video codec that is
technically identical to ISO/IEC International Standard 14496-10.
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The RTP payload format allows for packetization of one or more
Network Abstraction Layer (NAL) units, produced by the video
encoder, in each RTP payload. The payload format has wide
applicability, such as 3D video streaming, free-viewpoint video, and
3DTV.
Table of Contents
1. Introduction...................................................3
2. Conventions....................................................3
3. The MVC Codec..................................................4
3.1. Overview..................................................4
3.2. Parameter Set Concept.....................................5
3.3. Network Abstraction Layer Unit Header.....................5
4. Scope..........................................................8
5. Definitions and Abbreviations..................................8
5.1. Definitions...............................................8
5.1.1. Definitions per MVC specification....................8
5.1.2. Definitions local to this memo.......................9
5.1. Abbreviations.............................................9
6. MVC RTP Payload Format.........................................9
6.1. Design Principles.........................................9
6.2. RTP Header Usage.........................................10
6.3. Common Structure of the RTP Payload Format...............10
6.4. NAL Unit Header Usage....................................10
6.5. Packetization Modes......................................11
6.5.1. Packetization Modes for single-session transmission.11
6.5.2. Packetization Modes for multi-session transmission..12
6.6. Aggregation Packets......................................12
6.7. Fragmentation Units (FUs)................................12
6.8. Payload Content Scalability Information (PACSI) NAL Unit for
MVC...........................................................12
6.9. Non-Interleaved Multi-Time Aggregation Packets (NI-MTAPs)16
6.10. Cross-Session DON (CS-DON) for multi-session transmission16
7. Packetization Rules...........................................16
8. De-Packetization Process (Informative)........................18
9. Payload Format Parameters.....................................18
9.1. Media Type Registration..................................18
9.2. SDP Parameters...........................................20
9.2.1. Mapping of Payload Type Parameters to SDP...........20
9.2.2. Usage with the SDP Offer/Answer Model...............20
9.2.3. Usage with multi-session transmission...............20
9.2.4. Usage in Declarative Session Descriptions...........20
9.3. Examples.................................................20
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9.4. Parameter Set Considerations.............................20
10. Security Considerations......................................20
11. Congestion Control...........................................21
12. IANA Considerations..........................................21
13. Acknowledgments..............................................21
14. References...................................................21
14.1. Normative References....................................21
14.2. Informative References..................................22
Author's Addresses...............................................22
Intellectual Property Statement..................................23
Disclaimer of Validity...........................................23
15. Open issues:.................................................24
16. Changes Log..................................................24
1. Introduction
This memo specifies an RTP [RFC3550] payload format for a forthcoming
new mode of the H.264/AVC video coding standard, known as Multiview
Video Coding (MVC). Formally, MVC will take the form of Amendment 4
to ISO/IEC 14496 Part 10 [MPEG4-10], and Annex H of ITU-T Rec. H.264
[H.264]. The latest draft specification of MVC is available in [MVC].
MVC covers a wide range of 3D video applications, including 3D video
streaming, free-viewpoint video as well as 3DTV.
This memo follows a backward compatible enhancement philosophy, by
keeping as close an alignment to the H.264/AVC payload format
[RFC3984] as possible. It documents the enhancements relevant from
an RTP transport viewpoint, and defines signaling support for MVC,
including a new media subtype name.
Due to the similarity between MVC and SVC in system and transport
aspects, this memo reuses the design principles as well as many
features of the SVC RTP payload draft [I-D.draft-ietf-avt-svc].
[Ed.Note(TS):Need text on session multiplexing and on the relation of
this draft to [I-D.draft-ietf-avt-svc] here.]
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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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 that
bit the value of 1 (On). Clearing a bit is the same as assigning
that bit the value of 0 (Off).
3. The MVC Codec
3.1. Overview
MVC provides multi-view video bitstreams. An MVC bitstream contains
a base view conforming to at least one of the profiles of H.264/AVC
as defined in Annex A of [H.264], and one or more non-base views. To
enable high compression efficiency, coding of a non-base view can
utilize other views for inter-view prediction, thus its decoding
relies on the presence of the views it depends on. Each coded view
itself may be temporally scalable. Besides temporal scalability, MVC
also supports view scalability, wherein a subset of the encoded views
can be extracted, decoded and displayed, whenever it is desired by
the application.
The concept of video coding layer (VCL) and network abstraction layer
(NAL) is inherited from H.264/AVC. The VCL contains the signal
processing functionality of the codec; mechanisms such as transform,
quantization, motion-compensated prediction, loop filtering and
inter-layer prediction. The Network Abstraction Layer (NAL)
encapsulates each slice generated by the VCL into one or more Network
Abstraction Layer Units (NAL units). Please consult RFC 3984 for a
more in-depth discussion of the NAL unit concept. MVC specifies the
decoding order of NAL units.
In MVC, one access unit contains all NAL units pertaining to one
output time instance for all the views. Within one access unit, the
coded representation of each view, also named as view component,
consists of one or more slices.
The concept of temporal scalability is not newly introduced by SVC or
MVC, as profiles defined in Annex A of [H.264] already support it.
In [H.264], sub-sequences have been introduced in order to allow
optional use of temporal layers. SVC extended this approach by
advertising the temporal scalability information within the NAL unit
header or prefix NAL units, both were inherited to MVC.
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3.2. Parameter Set Concept
The parameter set concept was first specified in [H.264]. Please
refer to section 1.2 of [RFC3984] for more details. SVC introduced
some new parameter set mechanisms. MVC has inherited the parameter
set concept from [H.264].
In particular, a different type of sequence parameter set (SPS),
which is referred to as subset SPS, using a different NAL unit type
than "the old SPS" specified in [H.264] is used for non-base views,
while the base view still uses "the old SPS". Slices from different
views would be able to use either 1) the same sequence or picture
parameter set, or 2) different sequence or picture parameter sets.
The inter-view dependency and the decoding order of all the encoded
views are indicated in a new syntax structure, the SPS MVC extension,
included in each subset SPS.
3.3. Network Abstraction Layer Unit Header
An MVC NAL unit of type 20 or 14 consists of a header of four octets
and the payload byte string. MVC NAL units of type 20 are coded
slices of non-base views. A special type of an MVC NAL unit is the
prefix NAL unit (type 14) that includes descriptive information of
the associated H.264/AVC VCL NAL unit (type 1 or 5) that immediately
follows the prefix NAL unit.
MVC extends the one-byte H.264/AVC NAL unit header by three
additional octets. 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 view identification
information, the temporal layer identification information, and other
fields as discussed below.
The syntax and semantics of the NAL unit header are formally
specified in [MVC], 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 defined for the one-byte H.264/AVC NAL
unit header, while the semantics of some fields have changed
slightly, in a backward compatible way):
+---------------+
|0|1|2|3|4|5|6|7|
+-+-+-+-+-+-+-+-+
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|F|NRI| Type |
+---------------+
F: 1 bit
forbidden_zero_bit. H.264/AVC 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 future
prediction. Such NAL units can be discarded without risking the
integrity of the reference pictures in the same view. A value higher
than 00 indicates that the decoding of the NAL unit is required to
maintain the integrity of reference pictures in the same view, or
that the NAL unit contains parameter sets.
Type: 5 bits
nal_unit_type. This component specifies the NAL unit type.
In H.264/AVC, NAL unit types 14 and 20 are reserved for future
extensions. MVC uses these two NAL unit types. NAL unit type 14 is
used for prefix NAL unit, and NAL unit type 20 is used for coded
slice of non-base view. NAL unit types 14 and 20 indicate the
presence of three additional octets in the NAL unit header, 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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|I| PRID | VID | TID |A|V|O|
+---------------+---------------+---------------+
PRID: 6 bits
priority_id. This flag specifies a priority identifier for the NAL
unit. A lower value of PRID indicates a higher priority.
TID: 3 bits
temporal_id. This component specifies the temporal layer (or frame
rate) hierarchy. Informally put, a temporal layer consisting of view
component with a less temporal_id corresponds to a lower frame rate.
A given temporal layer typically depends on the lower temporal layers
(i.e. the temporal layers with less temporal_id values) but never
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depends on any higher temporal layer (i.e. a temporal layers with
higher temporal_id value).
A: 1 bit
anchor_pic_flag. This component specifies whether the view component
is an anchor picture (when equal to 1) or not (when equal to 0), as
specified in [MVC].
VID: 10 bits
view_id. This component specifies the view identifier of the view
the NAL unit belongs to.
I: 1 bit
idr_flag. This component specifies whether the view component is a
view instantaneous decoding refresh (V-IDR) picture for the view
(when equal to 1) or not (when equal to 0), as specified in [MVC].
V: 1 bit
inter_view_flag. This component specifies whether the view component
is used for inter-view prediction (when equal to 1) or not (when
equal to 0).
R: 1 bit
reserved_zero_one_bit. Reserved bit for future extension. R MUST be
equal to 0. Receivers SHOULD ignore the value of
reserved_zero_one_bit.
O: 1 bit
reserved_one_bit. Reserved bit for future extension. R shall be
equal to 1. Receivers SHOULD ignore the value of
reserved_zero_one_bit.
This memo reuses the same additional NAL unit types introduced in RFC
3984, which are presented in section 6.3. In addition, this memo
introduces one more NAL unit type, 30, as specified in section 6.8.
These NAL unit types are marked as unspecified in [MVC] and
intentionally reserved for use in systems specifications like this
memo. Moreover, this specification extends the semantics of F, NRI,
PRID, TID, A, and I as described in section 6.4.
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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 [MVC]. Likely, the applications of this specification
will be in the IP based multimedia communications fields including 3D
video streaming over IP, free-viewpoint video over IP, and 3DTV over
IP.
This specification allows, in a given RTP packet stream, to
encapsulate NAL units belonging to
o the base view only, detailed specification in [RFC3984], or
o one or more non-base views, or
o the base view and one or non-base views
[Ed.Note(YkW): To be extended to allow separate carriage of different
temporal layers in different RTP packet streams as in
[I-D.draft-ietf-avt-svc].]
5. Definitions and Abbreviations
5.1. Definitions
5.1.1. Definitions per MVC specification
This document uses the definitions of [MVC]. The following terms,
defined in [MVC], are summed up for convenience:
access unit: A set of NAL units always containing exactly one
primary coded picture with one or more view components. In addition
to the primary coded picture, an access unit may also contain one or
more redundant coded pictures, one auxiliary coded picture, or other
NAL units not containing slices or slice data partitions of a coded
picture. The decoding of an access unit always results in one decoded
picture. All slices or slice data partitions in an access unit have
the same value of picture order count.
prefix NAL unit: A NAL unit with nal_unit_type equal to 14 that
immediately precedes a NAL unit with nal_unit_type equal to 1, 5,
or 12. The NAL unit that succeeds the prefix NAL unit is also
referred to as the associated NAL unit. The prefix NAL unit contains
data associated with the associated NAL unit, which are considered to
be part of the associated NAL unit.
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5.1.2. Definitions local to this memo
MVC NAL unit: A NAL unit of NAL unit type 14 or 20 as specified in
Annex H of [MVC]. An MVC NAL unit has a four-byte NAL unit header.
operation point: An operation point of an MVC bitstream represents a
certain level of temporal and view scalability. An operation point
contains only those NAL units required for a valid bitstream to
represent a certain subset of views at a certain temporal level. An
operation point is described by the view_id values of the subset of
views, and the highest temporal_id.
multi-session transmission: The transmission mode in which the MVC
bitstream is transmitted over multiple RTP sessions, with each stream
having the same SSRC. These multiple RTP streams can be associated
using the RTCP CNAME, or explicit signalling of the SSRC used.
Dependency between RTP sessions MUST be signaled according to [I-
D.ietf-mmusic-decoding-dependency] and this memo.
single-session transmission: The transmission mode in which the MVC
bitstream is transmitted over a single RTP session, with a single
SSRC and separate timestamp and sequence number spaces.
[Ed.Note(TS):Need more definitions here.]
5.1. Abbreviations
In addition to the abbreviations defined in [RFC3984], the following
ones are defined.
MVC: Multiview Video Coding
CS-DON: Cross-Session Decoding Order Number
MST: multi-session transmission
PACSI: Payload Content Scalability Information
SST: single-session transmission
6. MVC RTP Payload Format
6.1. Design Principles
The following design principles have been observed:
o Backward compatibility with [RFC3984] wherever possible.
o As the MVC base view is H.264/AVC compatible, the base view or any
H.264/AVC compatible subset of it, when transmitted in its own RTP
packet stream, MUST be encapsulated using [RFC3984]. Requiring this
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has the desirable side effect that the transmitted data can be
received by [RFC3984] receivers and decoded by H.264/AVC decoders.
o Media-Aware Network Elements (MANEs) as defined in [RFC3984] are
signaling aware and rely on signaling information. MANEs have state.
o MANEs can aggregate multiple RTP streams, possibly from multiple
RTP sessions.
o MANEs can perform media-aware stream thinning. By using the
payload header information identifying Layers within an RTP session,
MANEs are able to remove packets from the incoming RTP packet stream.
This implies rewriting the RTP headers of the outgoing packet stream
and rewriting of RTCP Receiver Reports.
6.2. RTP Header Usage
Please see section 5.1 of [RFC3984].
6.3. Common Structure of the RTP Payload Format
Please see section 5.2 of [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,
TID, A and I according to this specification.
Note that, in the context of this section, "protecting a NAL unit"
means any RTP or network transport mechanism that could improve the
probability of success delivery of the packet conveying the NAL unit,
including applying a QoS-enabled network, forward error correction
(FEC), retransmissions, and advanced scheduling behavior, whenever
possible.
The semantics of F specified in section 5.3 of [RFC3984] also applies
herein.
For NRI, for a bitstream conforming to one of the profiles defined in
Annex A of [H.264] and transported using [RFC3984], the semantics
specified in section 5.3 of [RFC3984] are applicable, i.e., NRI also
indicates the relative importance of NAL units. In MVC context, in
addition to the semantics specified in Annex H of [MVC] are
applicable, NRI also indicate the relative importance of NAL units
within a view. MANEs MAY use this information to protect more
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important NAL units better than less important NAL units.
[Ed.Note(YkW): "MVC context" to be clearly specified.]
For PRID, the semantics specified in Annex H of [MVC] applies. Note
that 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 forward error correction (FEC) protection
mechanism. The importance for the decoding process decreases as the
PRID value increases.
For TID, in addition to the semantics specified in Annex H of [MVC],
according to this memo, values of TID indicate the relative
importance. A lower value of TID indicates a higher importance for
NAL units within a view. MANEs MAY use this information to protect
more important NAL units better than less important NAL units.
For A, in addition to the semantics specified in Annex H of [MVC],
according to this memo, MANEs MAY use this information to protect NAL
units with A equal to 1 better than NAL units with A equal to 0.
MANEs MAY also utilize information of NAL units with A equal to 1 to
decide when to forward more packets for an RTP packet stream. For
example, when it is sensed that view switching has happened such that
the operation point has changed, MANEs MAY start to forward NAL units
for a new target view only after forwarding a NAL unit with A equal
to 1 for the new target view.
For I, in addition to the semantics specified in Annex H of [MVC],
according to this memo, MANEs MAY use this information to protect NAL
units with I equal to 1 better than NAL units with I equal to 0.
MANEs MAY also utilize information of NAL units with I equal to 1 to
decide when to forward more packets for an RTP packet stream. For
example, when it is sensed that view switching has happened such that
the operation point has changed, MANEs MAY start to forward NAL units
for a new target view only after forwarding a NAL unit with I equal
to 1 for the new target view.
6.5. Packetization Modes
[Ed.Note(TS): Need to add text from [I-D.draft-ietf-avt-rtp-svc] to
this section with respect to MVC.]
6.5.1. Packetization Modes for single-session transmission
This section will address the issues of section 4.5.1 and 5.1 of [I-
D.draft-ietf-avt-rtp-svc].
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6.5.2. Packetization Modes for multi-session transmission
This section will address the issues of section 4.5.2 and 5.2 of [I-
D.draft-ietf-avt-rtp-svc].
6.6. Aggregation Packets
This section will address the issues of section 4.7 of [I-D.draft-
ietf-avt-rtp-svc].
6.7. Fragmentation Units (FUs)
This section will address the issues of section 4.8 of [I-D.draft-
ietf-avt-rtp-svc].
6.8. Payload Content Scalability Information (PACSI) NAL Unit for MVC
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 view and temporal scalability information
and other characteristics that are common for all the remaining NAL
units in the payload of the aggregation packet. Furthermore, a PACSI
NAL unit MAY include a DONC field and contain zero or more SEI NAL
units. PACSI NAL unit makes it easier for MANEs to decide whether to
forward/process/discard the aggregation packet containing the PACSI
NAL unit. Senders MAY create PACSI NAL units and receivers MAY
ignore them, or use them as hints to enable efficient aggregation
packet processing. Note that the NAL unit type for the PACSI NAL
unit is selected among those values that are unspecified in [MVC] and
[RFC3984].
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 and payload header
fields of the aggregation packet 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
(MTAP), the decoding order number (DON) for the PACSI NAL unit MUST
be set to indicate that the PACSI NAL unit has an identical DON to
the first NAL unit in decoding order among the remaining NAL units in
the aggregation packet.
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The structure of a PACSI NAL unit is as follows. The first four
octets are exactly the same as the four-byte MVC NAL unit header as
discussed in section 3.3. They are followed by two always present
octet, two optional octets, and zero or more SEI NAL units, each SEI
NAL unit preceded by a 16-bit unsigned size field (in network byte
order) that indicates the size of the following NAL unit in bytes
(excluding these two octets, but including the NAL unit type octet of
the SEI NAL unit). Figure 1 illustrates the PACSI NAL unit structure
and an example of a PACSI NAL unit containing two SEI NAL units.
The bits P, C, S, and E are specified only if the bit X is equal to
1. The T bit MUST NOT be equal to 1 if the aggregation packet
containing the PACSI NAL unit is not an STAP-A packet. The T bit MAY
be equal to 1 if the aggregation packet containing the PACSI NAL unit
is an STAP-A packet. The field DONC MUST NOT be present if the T bit
is equal to 0, and MUST be present if the T bit is equal to 1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|NRI| Type |S| PRID | TID |A| VID |I|V|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X|T|RR |P|C|S|E| RRR | DONC (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAL unit size 1 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ SEI NAL unit 1 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAL unit size 2 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ SEI NAL unit 2 |
| |
| +-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. PACSI NAL unit structure
The values of the fields in PACSI NAL unit MUST be set as follows.
The term "target NAL units" are used in the semantics of some fields.
The target NAL units are such NAL units contained in the aggregation
packet, but not included in the PACSI NAL unit, that are within the
access unit to which the first NAL unit following the PACSI NAL unit
in the aggregation packet belongs.
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o The F bit MUST be set to 1 if the F bit in at least one of the
remaining NAL units in the aggregation packet 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 aggregation packet.
o The Type field MUST be set to 30.
o The S bit MUST be set to 1.
o The PRID field MUST be set to the lowest value of the PRID values
of all the remaining NAL units in the aggregation packet.
o The TID field MUST be set to the lowest value of the TID values of
all the remaining NAL units with the lowest value of VID in the
aggregation packet.
o The A bit MUST be set to 1 if the A bit of at least one of the
remaining NAL units in the aggregation packet is equal to 1.
Otherwise, the A bit MUST be set to 0.
o The VID field MUST be set to the lowest value of the VID values of
all the remaining NAL units in the aggregation packet.
o The I bit MUST be set to 1 if the I bit of at least one of the
remaining NAL units in the aggregation packet is equal to 1.
Otherwise, the I bit MUST be set to 0.
o The V bit MUST be set to 1 if the V bit of at least one of the
remaining NAL units in the aggregation packet is equal to 1.
Otherwise, the A bit MUST be set to 0.
o The R bit MUST be set to 0. Receivers SHOULD ignore the value of
R.
o If the X bit is equal to 1, the bits P, C, S, and E are specified
as below. Otherwise, the bits P, C, S, and E are unspecified, and
receivers MUST ignore these bits. The X bit SHOULD be identical for
all the PACSI NAL units involved in all the RTP sessions conveying an
MVC bitstream.
o The RR field MUST be set to '00' (in binary form). Receivers
SHOULD ignore the value of RR.
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o If the T bit is equal to 1, the OPTIONAL field DONC MUST be present
and specified as below. Otherwise, the field DONC MUST NOT be
present.
o The P bit MUST be set to 1 if all the remaining NAL units in the
aggregation packet are with redundant_pic_cnt higher than 0, i.e. the
slices are redundant slices. Otherwise, the P bit MUST be set to 0.
Informative note: The P bit indicates whether the packet can be
discarded because it contains only redundant slice NAL units.
Without this bit, the corresponding information can be concluded
from the syntax element redundant_pic_cnt, which is buried in the
variable-length coded slice header.
o The C bit MUST be set to 1 if the target NAL units belong to an
access unit for which the view components are intra coded.
Otherwise, the C bit MUST be set to 0. The C bit SHOULD be identical
for all the PACSI NAL units for which the target NAL units belong to
the same access unit.
Informative note: The C bit indicates whether the packet contains
intra slices which may be the only packets to be forwarded for a
fast forward playback, e.g. when the network condition is
extremely bad.
o The S bit MUST be set to 1, if the first VCL NAL unit, in
transmission order, of the view component containing the first NAL
unit following the PACSI NAL unit in the aggregation packet is
present in the aggregation packet. Otherwise, the S bit MUST be set
to 0.
o The E bit MUST be set to 1, if the last VCL NAL unit, in
transmission order, of the view component containing the first NAL
unit following the PACSI NAL unit in the aggregation packet is
present in the aggregation packet. Otherwise, the E field MUST be
set to 0.
Informative note: The S or E bit indicates whether the first or
last slice, in transmission order, of a view component is in the
packet, to enable a MANE to detect slice loss and take proper
action such as requesting a retransmission as soon as possible,
as well as to allow an efficient playout buffer handling
similarly as the M bit in the RTP header. The M bit in the RTP
header still indicates the end of an access unit, not the end of
a view component.
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o The RRR field MUST be set to '00000000'(in binary form). Receivers
SHOULD ignore the value of RRR.
o When present, the field DONC indicates the CL-DON value for the
first NAL unit in the STAP-A in transmission order.
SEI NAL units included in the PACSI NAL unit, if any, MUST contain a
subset of the SEI messages associated with the access unit of the
first NAL unit following the PACSI NAL unit within the aggregation
packet.
Informative note: Senders may repeat such SEI NAL units in the
PACSI NAL unit the presence of which in more than one packet is
essential for packet loss robustness. Receivers may use the
repeated SEI messages in place of missing SEI messages.
An SEI message SHOULD NOT be included in a PACSI NAL unit and
included in one of the remaining NAL units contained in the same
aggregation packet.
6.9. Non-Interleaved Multi-Time Aggregation Packets (NI-MTAPs)
This section will address the issues of section 4.7.1 of [I-D.draft-
ietf-avt-rtp-svc].
6.10. Cross-Session DON (CS-DON) for multi-session transmission
This section will address the issues of section 4.11 of [I-D.draft-
ietf-avt-rtp-svc].
7. Packetization Rules
[Ed.Note(TS): We need to adjust this section with respect to [I-
D.draft-ietf-avt-rtp-svc].]
Section 6 of [RFC3984] applies. The following rules apply in
addition.
All receivers MUST support the single NAL unit packetization mode to
provide backward compatibility to endpoints supporting only the
single NAL unit mode of RFC 3984. However, the single NAL unit
packetization mode SHOULD NOT be used whenever possible, because
encapsulating NAL units of small sizes, e.g. small NAL units
containing parameter sets, SEI messages or prefix NAL units, in their
own packets is typically less efficient because of the relatively big
overhead.
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All receivers MUST support the non-interleaved packetization mode.
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
MVC. More technically speaking, the implementation complexity
increase for providing the additional mechanisms of the non-
interleaved mode (namely STAP-A and FU-A) is minor, and the
benefits are great, that STAP-A implementation is required.
A NAL unit of small size SHOULD be encapsulated in an aggregation
packet together with one or more other NAL units. For example, non-
VCL NAL units such as access unit delimiter, parameter set, or SEI
NAL unit are typically small.
A prefix NAL unit SHOULD be aggregated to the same packet as the
associated NAL unit following the prefix NAL unit in decoding order.
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.
When an MVC bitstream is transported in more than one RTP session,
the following applies.
o Interleaved mode SHOULD be used for all the RTP sessions.
o An RTP session that does not use interleaved mode SHOULD be
constrained as follows.
- Non-interleaved mode MUST be used.
- STAP-A MUST be used, and any other type of packets MUST NOT be
used.
- Each STAP-A MUST contain a PACSI NAL unit and the DONC field MUST
be present in the PACSI NAL unit.
Informative note: The motivation for these constraints is to
allow the use of non-interleaved mode for the session conveying
the H.264/AVC compatible view, such that RFC 3984 receivers
without interleaved mode implementation can subscribe to the base
view session.
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Non-VCL NAL units SHOULD be conveyed in the same session as the
associated VCL NAL units. To meet this, SEI messages that are
contained in scalable nesting SEI message and are applicable to more
than one session SHOULD be separated and contained into multiple
scalable nesting SEI messages. The DON values MUST indicate the
cross-layer decoding order number values as if all these SEI messages
were in separate scalable nesting SEI messages and contained in the
beginning of the corresponding access units as specified in [MVC].
8. De-Packetization Process (Informative)
For a single RTP session, the de-packetization process specified in
section 7 of [RFC3984] applies.
For receiving more than one of multiple RTP sessions conveying a
scalable bitstream, an example of a suitable implementation of the
de-packetization process is to be specified similarly as what will be
finally included in [I-D.draft-ietf-avt-svc].
9. Payload Format Parameters
This section specifies the parameters that MAY be used to select
optional features of the payload format and certain features of the
bitstream. The parameters are specified here as part of the media
type registration for the MVC codec. A mapping of the parameters
into the Session Description Protocol (SDP) [RFC4566] is also
provided for applications that use SDP. Equivalent parameters could
be defined elsewhere for use with control protocols that do not use
SDP.
9.1. Media Type Registration
The media subtype for the MVC codec is allocated from the IETF tree.
The receiver MUST ignore any unspecified parameter.
Informative note: Requiring ignoring unspecified parameter allows
for backward compatibility of future extensions. For example, if
a future specification that is backward compatible to this
specification specifies some new parameters, then a receiver
according to this specification is capable of receiving data per
the new payload but ignoring those parameters newly specified in
the new payload specification. This sentence is also present in
RFC 3984.
Media Type name: video
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Media subtype name: H264-MVC
The media subtype "H264" MUST be used for RTP streams using RFC 3984,
i.e. not using any of the new features introduced by this
specification compared to RFC 3984. For RTP streams using any of the
new features introduced by this specification compared to RFC 3984,
the media subtype "H264-MVC" SHOULD be used, and the media subtype
"H264" MAY be used. Use of the media subtype "H264" for RTP streams
using the new features allows for RFC 3984 receivers to negotiate and
receive H.264/AVC or MVC streams packetized according to this
specification, but to ignore media parameters and NAL unit types it
does not recognize.
Required parameters: none
OPTIONAL parameters: to be specified.
Encoding considerations:
This type is only defined for transfer via RTP (RFC 3550).
Security considerations:
See section 10 of RFC XXXX.
Public specification:
Please refer to RFC XXXX and its section 14.
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: NN
Change controller:
IETF Audio/Video Transport working group delegated from the IESG.
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9.2. SDP Parameters
9.2.1. Mapping of Payload Type Parameters to SDP
The media type video/H264-MVC 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 H264-MVC (the
media subtype).
The clock rate in the "a=rtpmap" line MUST be 90000.
The OPTIONAL parameters, when present, MUST be included in the
"a=fmtp" line of SDP. These parameters are expressed as a 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 multi-session transmission
If multi-session transmission is used, the rules on signaling media
decoding dependency in SDP as defined in
[I-D.draft-ietf-mmusic-decoding-dependency] apply.
9.2.4. Usage in Declarative Session Descriptions
TBD.
9.3. Examples
TBD.
9.4. Parameter Set Considerations
Please see section 10 of [RFC3984].
10. Security Considerations
Please see section 11 of [RFC3984].
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11. Congestion Control
TBD.
12. IANA Considerations
Request for media type registration to be added.
13. Acknowledgments
TBD.
This document was prepared using 2-Word-v2.0.template.dot.
14. References
14.1. Normative References
[H.264] ITU-T Recommendation H.264, "Advanced video coding for
generic audiovisual services", 3rd Edition, November 2007.
[I-D.draft-ietf-avt-rtp-svc] Wenger, S., Wang, Y. -K., Schierl, T.
and A. Eleftheriadis, "RTP payload format for SVC video",
draft-ietf-avt-rtp-svc-13 (work in progress), July 2008.
[I-D.draft-ietf-mmusic-decoding-dependency] Schierl, T., and Wenger,
S., "Signaling media decoding dependency in Session
Description Protocol (SDP)", draft-ietf-mmusic-decoding-
dependency-02 (work in progress), May 2008.
[MPEG4-10]
ISO/IEC International Standard 14496-10:2005.
[MVC] Joint Video Team, "Joint Draft 7 of MVC ", available from
http://ftp3.itu.ch/av-arch/jvt-site/2008_04_Geneva/JVT-
AA209.zip, Geneva, Switzerland, April 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 3548, July 2003.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and Jacobson,
V., "RTP: A Transport Protocol for Real-Time Applications",
STD 64, RFC 3550, July 2003.
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[RFC3984] Wenger, S., Hannuksela, M., Stockhammer, T., Westerlund,
M., and Singer, D., "RTP Payload Format for H.264 Video",
RFC 3984, February 2005.
[RFC4566] Handley, M., Jacobson, V., and Perkins, C., "SDP: Session
Description Protocol", RFC 4566, July 2006.
14.2. 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] McCanne, S., Jacobson, V., and Vetterli, M., "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.
[RFC3450] Luby, M., Gemmell, J., Vicisano, L., Rizzo, L., and
Crowcroft, J., "Asynchronous layered coding (ALC) protocol
instantiation", RFC 3450, December 2002.
Author's Addresses
Ye-Kui Wang
Nokia Research Center
P.O. Box 100
33721 Tampere
Finland
Phone: +358-50-466-7004
EMail: ye-kui.wang@nokia.com
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Thomas Schierl
Fraunhofer HHI
Einsteinufer 37
D-10587 Berlin
Germany
Phone: +49-30-31002-227
EMail: schierl@hhi.fhg.de
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Copyright Statement
Copyright (C) The IETF Trust (2008).
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This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society. Further, the author Thomas Schierl of Fraunhofer
HHI is sponsored by the European Commission under the contract number
FP7-ICT-214063, project SEA.
15. Open issues:
- The use of CL-DON for session reordering allows also for
interleaved transmission with non-interleaved packetization mode.
There should be a clear separation between both tools. This issue
should be handled the same way as for the SVC payload draft.
- Since SVC session multiplexing (multi source transmission(MST)) is
cleared, it would be great to just reference the MST sections in
[I-D.draft-ietf-avt-rtp-svc]. Since the text in sections 6 and 7
of [I-D.draft-ietf-avt-rtp-svc] is currently very SVC specific,
the authors would have to try to rewrite these sections in a more
generic way. If this is not possible, we need to copy text from
[I-D.draft-ietf-avt-rtp-svc] with respect to MVC.
16. Changes Log
Initial version 00
10 November 2007: YkW
Initial version
12 November 2007: TS
- Added definition of "Session multiplexing"
- Added the reference of [I-D.draft-ietf-mmusic-decoding-
dependency], and its reference in section 9.2.3
12 November 2007: YkW
- Added the reference of [I-D.draft-ietf-avt-svc] and its
reference in section 1.
- Added in sections 3.1 and 3.2 paragraphs regarding inter-view
prediction
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From draft-wang-avt-rtp-mvc-00 to draft-wang-avt-rtp-mvc-01
18 February 2008: YkW
- Alignment to the latest MVC draft in JVT-Z209 and version 07
of [I-D.draft-ietf-avt-svc].
25 February 2008: TS
- Minor modifications and updates throughout the document
- Added open issue on clear separation between "decoding order
recovery" and "interleaving"
From draft-wang-avt-rtp-mvc-01 to draft-wang-avt-rtp-mvc-02
09 July 2008: TS
- Minor modifications and updates throughout the document
- Added open issue
- NAL unit header alignment with MVC spec
- Section 6. References corresponding sections in [RFC3984] and [I-
D.draft-ietf-avt-svc].
- TBD: Section 7, we may align [I-D.draft-ietf-avt-svc] in a way
that SVC is not mentioned in this paragraphs, so that we can
reference them from this document.
21 August 2008:
- Minor modifications, editing and adding notes throughout the
document.
- Updated references
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