Internet Draft S. Wenger
Document: draft-ietf-avt-rtp-h264-01.txt M.M. Hannuksela
Expires: August 2003 T. Stockhammer
February 2003
Expires August 2003
RTP payload Format for JVT Video
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
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Abstract
This memo describes an RTP Payload format for the ITU-T
Recommendation H.264 video codec. The most up-to-date draft of the
video codec was specified in February 2003, is due for final
approval at the committee level late March 2003, and is available
for public review [1]. This codec was designed as a joint project
of the Video Coding Experts Group (VCEG) of ITU-T and the Moving
Picture Experts Group (MPEG) of ISO/IEC. ISO/IEC International
Standard 14496-10 will be technically identical to ITU-T
Recommendation H.264.
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Table of Contents
1. Introduction......................................................3
1.1. The JVT codec..................................................3
1.2. Parameter Set Concept..........................................4
1.3. Network Abstraction Layer Packet (NALU) Types..................5
2. Conventions.......................................................6
3. Changes relative to draft-ietf-avt-rtp-h264-00.txt................6
3.1. Status of the JVT standardization, and recent changes to JVT...6
3.2. Changes relative to draft-ietf-avt-rtp-h264-00.txt.............6
4. Scope.............................................................6
5. Definitions.......................................................7
6. RTP Payload Format................................................7
6.1. RTP Header Usage...............................................7
6.2. Simple Packet..................................................8
6.3. Aggregation Packets............................................9
6.4. Fragmentation Units...........................................13
7. Packetization Rules..............................................14
7.1. Unrestricted Mode (Multiple Picture Model)....................15
7.2. Restricted Mode (Single Picture Model)........................16
8. De-Packetization Process.........................................16
9. MIME Considerations..............................................18
9.1. MIME Registration.............................................19
9.2. SDP Parameters................................................21
10. Security Considerations.........................................21
11. Informative Appendix: Application Examples......................22
11.1. Video Telephony, no Data Partitioning, no packet aggregation.22
11.2. Video Telephony, Interleaved Packetization using Packet
Aggregation........................................................22
11.3. Video Telephony, with Data Partitioning......................23
11.4. Low-Bit-Rate Streaming.......................................23
11.5. Robust Packet Scheduling in Video Streaming..................24
12. Open Issues.....................................................25
13. Full Copyright Statement........................................25
14. Intellectual Property Notice....................................25
15. References......................................................25
15.1. Normative References.........................................25
15.2. Informative References.......................................26
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1. Introduction
1.1. The JVT codec
This memo specifies an RTP payload specification for a new video
codec that is currently under development by the Joint Video Group
(JVT), which is formed of video coding experts of MPEG and the ITU-
T. After the likely approval by the two parent bodies, the codec
specification will have the status of the ITU-T Recommendation
H.264 and become part of the MPEG-4 specification (ISO/IEC 14496
Part 10). The current project timeline of the JVT project is such
that a technically frozen specification exists since February 2003
(pending bug fixes). It is believed that only very few, if any,
technical details will be changed that directly affect this draft
in the future.
Before JVT was formed in late 2001, this project used the ITU-T
project name H.26L and the JVT project inherited all the technical
concepts of the H.26L project.
The JVT video codec has a very broad application range that covers
the all forms of digital compressed video from low bit rate
Internet Streaming applications to HDTV broadcast and Digital
Cinema applications with near loss-less coding. Most, if not all,
relevant companies in all of these fields (including Video-
Conferencing, Streaming, TV broadcast, and Digital Cinema) have
participated in the standardization, which gives hope that this
wide application range is more than an illusion and may
materialize, probably in a relatively short time frame. The
overall performance of the JVT codec is as such that bit rate
savings of 50% or more, compared to the current state of
technology, are reported. Digital Satellite TV quality, for
example, was reported to be achievable at 1.5 Mbit/s, compared to
the current operation point of MPEG 2 video at around 3.5 Mbit/s
[5].
The codec specification [1] itself distinguishes conceptually
between a video coding layer (VCL), and a network abstraction layer
(NAL). The VCL contains the signal processing functionality of the
codec, things such as transform, quantization, motion
search/compensation, and the loop filter. It follows the general
concept of most of today's video codecs, a macroblock-based coder
that utilizes inter picture prediction with motion compensation,
and transform coding of the residual signal. The output of the VCL
are slices: a bit string that contains the macroblock data of an
integer number of macroblocks, and the information of the slice
header (containing the spatial address of the first macroblock in
the slice, the initial quantization parameter, and similar).
Macroblocks in slices are ordered in scan order unless a different
macroblock allocation is specified, using the so-called Flexible
Macroblock Ordering syntax. In-picture prediction is used only
within a slice.
The NAL encapsulates the slice output of the VCL into Network
Abstraction Layer Units (NALUs), which are suitable for the
transmission over packet networks or the use in packet oriented
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multiplex environments. JVT's Annex B defines an encapsulation
process to transmit such NALUs over byte-stream oriented networks.
In the scope of this memo Annex B is not relevant.
Neither VCL nor NAL are claimed to be media or network independent
- the VCL needs to know transmission characteristics in order to
appropriately select the error resilience strength, slice size,
etc., whereas the NAL needs information like the importance of a
bit string provided by the VCL to select the appropriate
application layer protection.
Internally, the NAL uses NAL Units or NALUs. A NALU consists of a
one-byte header and the payload byte string. The header co-serves
as the RTP payload header and indicates the type of the NALU, the
(potential) presence of bit errors in the NALU payload, and
information regarding the relative importance of the NALU for the
decoding process. This RTP payload specification is designed to be
unaware of the bit string in the NALU payload.
One of the main properties of the JVT codec is the complete
decoupling of the transmission time, the decoding time, and the
sampling or presentation time of slices and pictures. The codec
itself is unaware of time, and does not carry information such as
the number of skipped frames (as common in the form of the Temporal
Reference in earlier video compression standards). Also, there are
NAL units that are affecting many pictures and are, hence,
inherently time-less. For this reason, the handling of the RTP
timestamp requires some special considerations for those NALUs for
which the sampling or presentation time is not defined, or, at
transmission time, unknown.
1.2. Parameter Set Concept
One very fundamental design concept of the JVT codec is to generate
self-contained packets, to make mechanisms such as the header
duplication of RFC2429 [6] or MPEG-4's HEC [7] unnecessary. The
way how this was achieved is to decouple information that is
relevant to more than one slice from the media stream. This higher
layer meta information should be sent reliably, asynchronously and
in advance from the RTP packet stream that contains the slice
packets. (Provisions for sending this information in-band are also
available for such applications that do not have an out-of-band
transport channel appropriate for the purpose). The combination of
the higher level parameters is called a Parameter Set. The
Parameter Set contains information such as
o picture size,
o display window,
o optional coding modes employed,
o macroblock allocation map,
o and others.
In order to be able to change picture parameters (such as the
picture size), without having the need to transmit Parameter Set
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updates synchronously to the slice packet stream, the encoder and
decoder can maintain a list of more than one Parameter Set. Each
slice header contains a codeword that indicates the Parameter Set
to be used.
This mechanism allows to decouple the transmission of the Parameter
Sets from the packet stream, and transmit them by external means,
e.g. as a side effect of the capability exchange, or through a
(reliable or unreliable) control protocol. It may even be possible
that they get never transmitted but are fixed by an application
design specification.
Although, conceptually, the Parameter Set updates are not designed
to be sent in the synchronous packet stream, this memo contains
means to convey them in the RTP packet stream.
1.3. Network Abstraction Layer Packet (NALU) Types
Tutorial information on the NAL design can be found in [8],
[9] and [10]. For the precise definition of the NAL it is referred
to [1].
All NALUs consist of a single NALU Type octet, which also co-serves
as the payload header. The payload of a NALU follows immediately.
The NALU type octet has the following format:
+---------------+
|0|1|2|3|4|5|6|7|
+-+-+-+-+-+-+-+-+
|F|NRI| Type |
+---------------+
F: 1 bit
The Forbidden bit, when zero, indicates a bit error free NAL
unit. The JVT specification declares a value of 1 as a syntax
violation. Hence, when set, the decoder is advised that bit
errors may be present in the payload or in the NALU type octet.
A prudent reaction of decoders that are incapable of handling
bit errors is to discard such packets.
NRI: 2 bits
NAL Reference IDC. A value of 00 indicates that the content of
the NALU is not used to reconstruct stored pictures (that can be
used for future reference). Such NALUs can be discarded without
risking the integrity of the reference pictures. Values above
00 indicate that the decoding of the NALU is required to
maintain the integrity of the reference pictures. Furthermore,
values above 00 indicate the relative transport priority, as
determined by the encoder. Intelligent network elements can use
this information t protect more important NALUs better than less
important NALUs. 11 is the highest transport priority, followed
by 10, then by 01 and, finally, 00 is the lowest.
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Type: 5 bits
The NAL Unit payload type as defined in table 7.1 of [1], and
later within this memo. Note that the NAL unit types defined in
this memo are marked as reserved for external use in [1].
For a reference of all currently defined NALU types and their
semantics please refer to section 7.4.1 in [1]. In particular,
note that VCL NAL units refer to coded slice and data partition NAL
units as well as filler data NAL units.
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 RFC 2119 [2].
3. Changes relative to draft-ietf-avt-rtp-h264-00.txt
[This section will be removed in a future version of this draft.]
3.1. Status of the JVT standardization, and recent changes to JVT
None that affect this draft.
3.2. Changes relative to draft-ietf-avt-rtp-h264-00.txt
This memo contains the following technical changes relative to the
previous I-D:
o The MTAPs with timestamp offset lengths of 8 and 32 bits are
removed, as discussed in Atlanta.
o The remarks about application layer protection are aligned with
the current thinking of the AVT group re congestion control.
o A fragmentation NALU has been introduced to allow fragmenting
long NALUs into several RTP packets.
o Recovering the decoding order of NALUs carried in MTAPs is
clarified and transmission of NALUs out of decoding order is
allowed, which can be used for robust packet scheduling in
streaming systems (see section 11.5 for further details).
o The rule of assigning the RTP timestamp to non-slice NALUs has
been changed: The RTP timestamp is set to the RTP timestamp of
the primary coded picture to which the NALU is associated
according to section 7.4.1.2 of [1].
o MIME type registration and SDP usage have been specified.
4. Scope
This payload specification can only be used to carry the "naked"
JVT NALU stream over RTP. Likely, the first applications of a
Standard Track RFC resulting from this draft will be in the
conversational multimedia field, video telephone or video
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conference. The draft is not intended for the use in conjunction
with the Byte Stream format of Annex B of the JVT working draft.
5. Definitions
This document uses the definitions of [1]. In addition, the
following definitions apply:
NAL unit decoding order: A NAL unit order that conforms to the
constraints on NAL unit order given in section 7.4.1.1 in [1].
Transmission order: The order of packets in ascending RTP sequence
number order (in modulo arithmetic). Within an Aggregation Packet,
the NAL unit transmission order is the same as the order of
appearance of NAL units in the packet.
6. RTP Payload Format
6.1. RTP Header Usage
The format of the RTP header is specified in RFC 1889 [3] and
reprinted in Figure XXXX for convenience. This payload format uses
the fields of the header in a manner consistent with that
specification.
When encapsulating one NALU per RTP packet, the RECOMMENDED RTP
payload is specified in section 6.2. The RTP payload (and the
settings for some RTP header bits) for aggregation packets and
fragmentation units are specified in sections 6.3 and 6.4,
respectively.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P|X| CC |M| PT | sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| synchronization source (SSRC) identifier |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| contributing source (CSRC) identifiers |
| .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure xxxx: RTP header according to RFC 1889.
The RTP header information is set as follows:
Version (V): 2 bits
Set to 2 according to RFC 1889.
Padding (P): 1 bit
Used according to RFC 1889.
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Extension (X): 1 bit
Specified in the RTP profile in use.
CSRC count (CC): 4 bits
Used according to RFC 1889.
Marker bit (M): 1 bit
Set for the very last packet of the picture indicated by the RTP
timestamp, in line with the normal use of the M bit and to allow
an efficient playout buffer handling. Decoders MAY use this bit
as an early indication of the last packet of a coded picture,
but MUST not rely on this property because the last packet of
the picture may get lost, and because the use of MTAPs does not
always preserve the M bit.
Payload type (PT): 7 bits
The assignment of an RTP payload type for this new packet format
is outside the scope of this document, and will not be specified
here. It is expected that the RTP profile under which this
payload format is being used will assign a payload type for this
encoding or specify that the payload type is to be bound
dynamically.
Sequence number (SN): 16 bit
Increased by one for each sent packet. Set to a random value
during startup as per RFC1889
Timestamp: 32 bits
The RTP timestamp is set to the sampling timestamp of the
content. If the NALU has no own timing properties (e.g.
parameter set and SEI NAL units), the RTP timestamp is set to
the RTP timestamp of the primary coded picture to which the NALU
is associated according to section 7.4.1.2 of [1]. The setting
of the RTP Timestamp for MTAPs is defined in section 6.3.2
above.
Synchronization source (SSRC) identifier: 32 bits
Used according to RFC 1889.
Contributing source (CSRC) identifiers: 0 to 15 items, 32 bits each
Used according to RFC 1889.
6.2. Simple Packet
The RTP payload of a Simple Packet according to this specification
consists of one NALU as depicted in Figure xxxx. The type of the
NALU MUST be specified in [1], i.e., the NALU MUST NOT be an
aggregation packet or a fragmentation unit. A NAL unit stream
composed by decapsulating Simple Packets in RTP sequence number
order MUST conform to the NAL unit decoding order.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| NALU |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :...OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure xxxx. RTP payload format for Simple Packet.
6.3. Aggregation Packets
Aggregation packets are the packet aggregation scheme of this
payload specification. The scheme is introduced to reflect the
dramatically different MTU sizes of two key target networks --
wireline IP networks (with an MTU size that is often limited by the
Ethernet MTU size -- roughly 1500 bytes), and IP or non-IP (e.g.
H.324/M) based wireless networks with preferred transmission unit
sizes of 254 bytes or less. In order to prevent media transcoding
between the two worlds, and to avoid undesirable packetization
overhead, a packet aggregation scheme is introduced.
Two types of Aggregation packets are defined by this specification:
o Single-Time Aggregation Packet (STAP) aggregate NALUs with
identical NALU-time.
o Multi-Time Aggregation Packets (MTAP) aggregate NALUs with
potentially differing NALU-time. Two different MTAPs are defined
that differ in the length of the NALU timestamp offset.
The term NALU-time is defined as the value the RTP timestamp would
have if that NALU would be transported in its own RTP packet.
The structure of the RTP payload format for aggregation packets is
presented in Figure xxxx.
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 | |
+-+-+-+-+-+-+-+-+ |
| |
| NALU payload |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :...OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure xxxx. RTP payload format for aggregation packets.
MTAPs and STAP share the following packetization rules: The RTP
timestamp MUST be set to the minimum of the NALU times of all the
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NALUs to be aggregated. The Type field of the NALU type octet MUST
be set to the appropriate value as indicated in table xxx. The F
bit MUST be cleared if all F bits of the aggregated NALUs are zero,
otherwise it MUST be set.
Table xxx: Type field for STAP and MTAPs
Type Packet Timestamp offset field length (in bits)
----------------------------------------------
0x18 STAP 0
0x19 MTAP16 16
0x20 MTAP24 24
The Marker bit in the RTP header MUST be set to the value the
marker bit of the last NALU of the aggregated packet would have if
it were transported in its own RTP packet.
The NALU Payload of an aggregation packet consists of one or more
aggregation units. See section 6.3.1 and 6.3.2 for the two
different types of aggregation units. An aggregation packet can
carry as many aggregation units as necessary, however the total
amount of data in an aggregation packet obviously MUST fit into an
IP packet, and the size SHOULD be chosen such that the resulting IP
packet is smaller than the MTU size. An aggregation packet MUST
NOT contain fragmentation units specified in section 6.4.
A NAL unit stream composed by decapsulating Aggregation Packets in
RTP sequence number order is NOT REQUIRED to conform to the NAL
unit decoding order. Requirements on the NAL unit transmission
order are specified in section 7 and means to recover the NAL unit
decoding order are given in section 8.
6.3.1. Single-Time Aggregation Packet
Single-Time Aggregation Packet (STAP) SHOULD be used whenever
aggregating NALUs that share the same NALU-time. The NALU payload
of an STAP consists of a 16-bit unsigned decoding order number
(DON) followed by at least one Single-Picture Aggregation Unit as
presented in Figure XXXX.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: decoding order number (DON) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| single-picture aggregation units |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure xxxx. NALU payload format for STAP.
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DON indicates the NAL unit decoding order specified in this
document. The DON of the first NALU in transmission order MAY be
set to any value. Let DON of one NAL unit be D1 and DON of another
NAL unit be D2. If D1 < D2 and D2 - D1 < 32768, or if D1 > D2 and
D1 . D2 >= 32768, then the NAL unit having DON equal to D1 precedes
the NAL unit having DON equal to D2 in NAL unit decoding order. If
D1 < D2 and D2 - D1 >= 32768, or if D1 > D2 and D1 - D2 < 32768,
then the NAL unit having DON equal to D2 precedes the NAL unit
having DON equal to D1 in NAL unit decoding order. NAL units
associated with different primary coded pictures according to
subclause 7.4.1.2 of [1] MUST NOT have the same value of DON. NAL
units associated with the same primary coded picture according to
subclause 7.4.1.2 of [1] MAY have the same value of DON. If all
NAL units of a primary coded picture have the same value of DON,
NAL units of a redundant coded picture associated with the primary
coded picture SHOULD have the same value of DON as the NAL units of
the primary coded picture. The NAL unit decoding order of NAL
units that have the same value of DON is the following:
1. Picture delimiter NAL unit, if any
2. Sequence parameter set NAL units, if any
3. Picture parameter set NAL units, if any
4. SEI NAL units, if any
5. Coded slice and slice data partition NAL units of the primary
coded picture, if any
6. Coded slice and slice data partition NAL units of the redundant
coded pictures, if any
7. Filler data NAL units, if any
8. End of sequence NAL unit, if any
9. End of stream NAL unit, if any
A Single-Picture Aggregation Unit consists of 16-bit unsigned size
information that indicates the size of the following NALU in bytes
(excluding these two octets, but including the NALU type octet of
the NALU), followed by the NALU itself including its NALU type
byte. A Single-Picture Aggregation Unit is byte-aligned within the
RTP payload but it may not be aligned on a 32-bit word boundary.
Figure xxxx presents the structure of the Single-Picture
Aggregation Unit.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: NALU size | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| NALU |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure xxxx. Structure for single-picture aggregation unit.
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6.3.2. Multi-Time Aggregation Packets (MTAPs)
The NALU payload of MTAPs consists of a 16-bit unsigned decoding
order number base (DONB) and one or more Multi-Picture Aggregation
Units as presented in Figure xxxx. DONB MUST contain the smallest
value of DON among the NAL units of the MTAP. The choice between
the different MTAP fields is application dependent -- the larger
the timestamp offset is the higher is the flexibility of the MTAP,
but the higher is also the overhead.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: decoding order number base | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| multi-picture aggregation units |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure xxxx. NALU payload format for MTAPs.
Two different Multi-Time Aggregation Units are defined in this
specification. Both of them consist of 16 bits unsigned size
information of the following NALU, an 8-bit unsigned decoding
order number delta (DOND), and n bits of timing information for
this NALU, whereby n can be 16 or 24. The structure of the Multi-
Time Aggregation Units for MTAP16 and MTAP24 are presented in
figures XXXX and XXXX respectively. Note that the starting or
ending position of an aggregation unit within a packet is NOT
REQUIRED to be on a 32-bit word boundary. DON of the following
NALU is equal to DONB + DOND and MUST NOT be larger than 65535.
This memo does not specify how the NALUs within an MTAP are
ordered, but, in most cases, NAL unit decoding order, i.e.,
ascending order of DONDs, SHOULD be used. The timing information
field MUST be set so that the RTP timestamp of an RTP packet of
each NALU in the MTAP (the NALU-time) can be generated by adding
the timing information from the RTP timestamp of the MTAP.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: NALU size | DOND | timing info |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| timing info | |
+-+-+-+-+-+-+-+-+ NALU |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure xxxx: Multi-Time Aggregation Unit for MTAP16
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: NALU size | DOND | timing info |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| timing info | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| NALU |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure xxxx: Multi-Time Aggregation Unit for MTAP24
For the "earliest" multi-picture Aggregation Unit in an MTAP the
timing offset MUST be zero. Hence, the RTP timestamp of the MTAP
itself is identical to the earliest NALU-time.
6.4. Fragmentation Units
Fragmentation units (FU) are the packet fragmentation scheme of
this payload specification. Among others, the scheme is introduced
to complement the aggregation unit scheme introduced in section 6.3
and to deliver pre-encoded packetized video over networks with
limited MTU size. FUs contain fragments of one single NALU, which
is referred to as fragmented NALU. STAPs and MTAPs MUST NOT be
fragmented.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|NALU type octet| FU header | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| FU payload |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :...OPTIONAL RTP padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure xxxx. RTP payload format for Fragmentation Unit.
The NALU type octet of a fragmentation unit is indicated by the
type definition 0x21 and has the following format:
+---------------+
|0|1|2|3|4|5|6|7|
+-+-+-+-+-+-+-+-+
|F|NRI| 0x21 |
+---------------+
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The NALU payload of a fragmentation unit consists of fragmentation
unit header of one octet and a fragmentation unit payload. The FU
header has the following format:
+---------------+
|0|1|2|3|4|5|6|7|
+-+-+-+-+-+-+-+-+
|S|E|R| Type |
+---------------+
S: 1 bit
The Start bit, when one, indicates the start of a fragmented
NALU. Otherwise, when the following payload is not the start of
an NALU payload, the Start bit is set to zero.
E: 1 bit
The End bit, when one, indicates the end of a fragmented NALU,
i.e. the last byte of the payload is also the last byte of the
fragmented NALU. Otherwise, when the following payload is not
the last FU of a fragmented NALU, the End bit is set to zero.
R: 1 bit
The Reserved bit MUST be 0.
Type: 5 bits
The NAL Unit payload type as defined in table 7.1 of [1].
The FU payload consists of fragments of the payload of the
fragmented NALU such that if the fragmentation unit payloads of
consecutive FUs are sequentially concatenated, the payload of the
fragmented NALU is reconstructed. Note that the NALU type octet of
the fragmented NALU is not included as such in the fragmentation
unit payload, but rather the information of the NALU type octet of
the fragmented NALU is conveyed in F and NRI fields of the NALU
type octet of the fragmentation unit and in the type field of the
FU header. A FU payload can have any number of octets and can be
empty.
The following rules apply to fields in the RTP header and in the
NALU type octet of the RTP payload: The RTP timestamp is set to
the NALU time of the fragmented NALU. The F bit MUST be set
according to the F bit of the fragmented NALU. The value of NRI
field MUST be set according to the value of the NRI field in the
fragmented NALU.
7. Packetization Rules
Two cases of packetization rules have to be distinguished by the
possibility to put packets belonging to more than a single picture
into a single aggregated packet (using STAPs or MTAPs).
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7.1. Unrestricted Mode (Multiple Picture Model)
This mode MAY be supported by some receivers. Usually, the
capability of a receiver to support this mode is implied by the
application, or indicated by external control protocol means. The
use of this mode MUST be signaled with the optional aggregation-
mode MIME or SDP parameter, if MIME or SDP signaling is in use.
The following packetization rules MUST be enforced by the sender:
o Single slice NALUs or Data Partition NALUs belonging to the same
picture (and hence share the same RTP timestamp value) MAY be
sent in any order permitted by the applicable profile defined in
[1], although, for delay critical systems, they SHOULD be sent in
their original coding order to minimize the delay. Note that the
coding order is not necessarily the scan order, but the order the
NAL packets become available to the RTP stack.
o The transmission order of NALUs MUST conform to the NAL unit
decoding order unless signaled otherwise with the optional num-
reorder-VCL-NAL-units MIME parameter or by other means. Some
receivers MAY NOT support a transmission order that does not
conform to the NAL unit decoding order.
o Both MTAPs and STAPs MAY be used.
o FUs MAY be used. If an NALU is transmitted as a fragmented NALU,
the following rules apply. For the first FU of a fragmented NALU
the Start bit is set to one, the End bit is set to zero, and any
number of initial bytes of the fragmented NALU payload are
transported in this FU. Any number of additional FUs belonging to
this fragmented NALU may be transmitted with Start bit set to
zero and End bit set to zero. If the FU contains the last byte of
the fragmented NALU, the End bit is set to one. A fragmented NALU
MUST NOT be transmitted in one FU, i.e., Start bit and End bit
MUST NOT both be set to one in the same FU header. A
Fragmentation Unit MUST NOT contain an aggregation packet.
Fragmentation units of a NALU MUST be sent in consecutive
packets.
o SEI packets MAY be sent anytime.
o Parameter set NALUs MUST NOT be sent in an RTP session whose
Parameter Sets were already changed by control protocol messages
during the lifetime of the RTP session. If parameter set NALUs
are allowed by this condition, they MAY be sent at any time.
o An MTAP or a STAP MUST NOT contain an FU.
o An Aggregation Packet MUST succeed a Simple Packet in
transmission order if the NAL units in the Simple Packet precede
the NAL units in the Aggregation Packet in NAL unit decoding
order. An Aggregation Packet MUST precede a Simple Packet in
transmission order if the NAL units in the Simple Packet succeed
the NAL units in the Aggregation Packet in NAL unit decoding
order.
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o An Aggregation Packet MUST succeed a Fragmentation Unit in
transmission order if the NAL units in the Simple Packet precede
the NAL unit conveyed in the Fragmentation Unit in NAL unit
decoding order. An Aggregation Packet MUST precede a
Fragmentation Unit in transmission order if the NAL unit conveyed
in the Fragmentation Unit succeed the NAL units in the
Aggregation Packet in NAL unit decoding order.
o All NALU types MAY be mixed freely, provided that above rules are
obeyed. In particular, it is allowed to mix slices in data-
partitioned and single-slice mode.
o Network elements MAY convert multiple RTP packets carrying
individual NALUs into one aggregated RTP packet, convert an
aggregated RTP packet into several RTP packets carrying
individual NALUs, or mix both concepts. However, when doing so
they SHOULD take into account at least the following parameters:
path MTU size, unequal protection mechanisms (e.g. through
packet-based FEC according to RFC2398, carried by RFC2198,
especially for parameter set NALUs and Type A Data Partitioning
NALUs), bearable latency of the system, and buffering
capabilities of the receiver.
o NALUs of all types except for FUs MAY be conveyed as aggregation
units of an STAP or MTAP rather than individual RTP packets.
Special care SHOULD be taken (particularly in gateways) to avoid
more than a single copy of identical NALUs in a single STAP/MTAP
in order to avoid unnecessary data transfers without any
improvements of QoS.
7.2. Restricted Mode (Single Picture Model)
This mode MUST be supported by all receivers. It is primarily
intended for low delay applications. Its main difference from the
Unrestricted Mode is to forbid the packetization of data belonging
to more than one picture in a single RTP packet. Hence, MTAPs MUST
NOT be used. The following packetization rules MUST be enforced by
the sender:
o All rules of the Unrestricted Mode above, with the following
additions
o only STAPs MAY be used, MTAPs MUST NOT be used. This implies that
aggregated packets MUST NOT include slices or data partitions
belonging to different pictures.
8. De-Packetization Process
The de-packetization process is implementation dependent. Hence,
the following description should be seen as an example of a
suitable implementation. Other schemes MAY be used as well.
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Optimizations relative to the described algorithms are likely
possible.
The general concept behind these de-packetization rules is to
reorder NALUs from transmission order to the NAL unit decoding
order. All fragmentation units of a NALU are collected and the
resulting NALU is processed as if it were received as a Simple
Packet. Aggregation packets are handled by unloading their payload
into individual RTP packets carrying NALUs. Those NALUs are
processed as if they were received in separate RTP packets, in the
order they were arranged in the Aggregation Packet.
Hereinafter, let N be the value of the optional num-reorder-VCL-
NAL-units MIME type parameter (see section 9.1). When the RTP
session is initialized, the receiver buffers at least N VCL NAL
units before passing any packet to the decoder.
For each NAL unit stored in the buffer, the RTP sequence number of
the packet that contained the NAL unit is stored and associated
with the stored NAL unit. Moreover, the packet type (Simple Packet
or Aggregation Packet) that contained the NAL unit is stored and
associated with each stored NAL unit. Furthermore, for NAL units
carried in aggregation packets, decoding order number (DON) is
calculated and stored.
If the receiver buffer contains at least N VCL NAL units, NAL units
are removed from the receiver buffer and passed to the decoder in
the order specified below until the buffer contains N-1 VCL NAL
units.
Hereinafter, let PDON be the DON of the previous NAL unit of an
aggregation packet in NAL unit decoding order. If no previous NAL
unit of an aggregation packet in NAL unit decoding order exists,
PDON is 0.
The order that NAL units are passed to the decoder is specified as
follows:
o If the oldest RTP sequence number in the buffer corresponds to a
Simple Packet, the NALU in the Simple Packet is the next NALU in
the NAL unit decoding order.
o If the oldest RTP sequence number in the buffer corresponds to an
Aggregation Packet, the NAL unit decoding order is recovered
among the NALUs conveyed in Aggregation Packets in RTP sequence
number order until the next Simple Packet or FU (exclusive).
This set of NALUs is hereinafter referred to as the candidate
NALUs. If no NALUs conveyed in Simple Packets or FUs reside in
the buffer, all NALUs belong to candidate NALUs.
o For each NAL unit among the candidate NALUs, a DON distance is
calculated as follows. If the DON of the NAL unit is larger than
PDON, the DON distance is equal to DON - PDON. Otherwise, the
DON distance is equal to 65535 - PDON + DON + 1. NAL units are
delivered to the decoder in ascending order of DON distance.
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o If several NAL units share the same DON distance, the order to
pass them to the decoder is the following:
1. Picture delimiter NAL unit, if any
2. Sequence parameter set NAL units, if any
3. Picture parameter set NAL units, if any
4. SEI NAL units, if any
5. Coded slice and slice data partition NAL units of
the primary coded picture, if any
6. Coded slice and slice data partition NAL units of
the redundant coded pictures, if any
7. Filler data NAL units, if any
8. End of sequence NAL unit, if any
9. End of stream NAL unit, if any
o If the video decoder in use does not support Arbitrary Slice
Ordering, the decoding order of slices and A data partitions is
ordered in ascending order of the first_mb.in.slice syntax
element in the slice header. Moreover, B and C data partitions
immediately follow the corresponding A data partition in decoding
order.
The following additional de-packetization rules MAY be used to
implement an operational JVT de-packetizer:
o Intelligent RTP receivers (e.g. in Gateways) MAY identify lost
DPAs. If a lost DPA is found, the Gateway MAY decide not to send
the DPB and DPC partitions, as their information is meaningless
for the JVT Decoder. In this way a network element can reduce
network load by discarding useless packets, without parsing a
complex bit stream
o Intelligent receivers MAY discard all packets that have a NAL
Reference Idc of 0. However, they SHOULD process those packets
if possible, because the user experience may suffer if the
packets are discarded.
o If a Fragmentation Unit is lost, all Fragmentation Units
corresponding to the same NALU SHOULD be discarded.
9. Payload Format Parameters
This section specifies the parameters that MAY be used to select
optional features of the payload format. The parameters are
specified here as part of the MIME subtype registration for the
ITU-T H.264 | ISO/IEC 14496-10 codec. A mapping of the parameters
into the Session Description Protocol (SDP) [4] is also provided
for those applications that use SDP. Equivalent parameters could
be defined elsewhere for use with control protocols that do not use
MIME or SDP.
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9.1. MIME Registration
The MIME subtype for the ITU-T H.264 | ISO/IEC 14496-10 codec is
allocated from the IETF tree.
Any unspecified parameter MUST be ignored by the receiver.
Media Type name: video
Media subtype name: H264
Required parameters: none
Optional parameters:
profile-level-id: A profile-level element used in specifying the
value of this parameter is generated by
forming a string of hexadecimal
representations of the following two bytes in
the sequence parameter set NAL unit specified
in [1]: 1) profile_idc and 2) level_idc. The
value of profile-level-id is a sequence of
profile-level elements. If this parameter is
used for indicating properties of a NAL unit
stream, it indicates the profiles that are in
use in the stream and the highest level that
is in use for each signaled profile. If this
parameter is used for capability exchange or
session setup procedure, it indicates the
profiles that the codec supports and the
highest level that is supported for each
signaled profile. For example, if a codec
supports the Baseline Profile at level 3 and
below and the Main Profile at level 2.1 and
below, the profile-level-id becomes 421E4D15.
If no profile-level-id is present, the
Baseline Profile at Level 1 MUST be implied.
profile-interoperability: This parameter MAY be used to signal
the properties of a NAL unit stream. It MUST
NOT be used to signal the capabilities of a
codec implementation. The parameter indicates
which ones of the coding tools that are
included in the Baseline Profile but are not
included in the Main Profile are in use in the
NAL unit stream. The value of the parameter
is a 3-character string of "1"s and "0"s
indicating the values of
more_than_one_slice_group_allowed_flag,
arbitrary_slice_order_allowed_flag, and
redundant_pictures_allowed_flag (respectively)
of the sequence parameter set NAL units that
are in use in the NAL unit stream. If the
value of any one of the flags in any of the
sequence parameter sets used in the NAL unit
stream changes, a value of "1" MUST be
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indicated in the value of the corresponding
flag in the profile-interoperability
parameter. If no profile-interoperability is
present, its value is undefined.
parameter-sets: This parameter MAY be used to convey such
parameter set NAL units, herein referred to as
the initial parameter set NAL units, that MUST
precede any other NAL units in decoding
order. The parameter MUST NOT be used to
indicate codec capability in any capability
exchange procedure. The value of the
parameter is the hexadecimal representation of
the initial parameter set NAL units as
specified in sections 7.3.2.1 and 7.3.2.2 of
[1]. The parameter sets are conveyed in
decoding order and no framing of the parameter
set NAL units takes place. Note that the
number of bytes in a parameter set NAL unit is
typically less than 10 bytes, but a picture
parameter set NALU can contain even several
hundreds of bytes.
num-reorder-VCL-NAL-units: This parameter MAY be used to signal
the properties of a NAL unit stream or the
capabilities of a transmitter or receiver
implementation. The parameter specifies the
maximum amount of VCL NAL units that precede
any VCL NAL unit in the NAL unit stream in NAL
unit decoding order and follow the VCL NAL
unit in RTP sequence number order or in the
composition order of the aggregation packet
containing the VCL NAL unit. If the parameter
is not present, num-reorder-VCL-NAL-units
equal to 0 MUST be implied. The value of num-
reorder-VCL-NAL-units MUST be an integer in
the range from 0 to 32767, inclusive.
aggregation-mode: Permissible values are 0 and 1. If 0 or not
present, STAPs MAY be present and MTAPs MUST
NOT be present in the NAL unit stream. If 1,
both STAPs and MTAPs MAY be present in the NAL
unit stream.
Encoding considerations:
This type is defined for transfer via RTP (RFC
1889).
Security considerations:
See section 10 of RFC XXXX.
Public specification:
Please refer to RFC XXXX and its section 15.
Additional information:
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None
File extensions: none
Macintosh file type code: none
Object identifier or OID: none
Person & email address to contact for further information:
stewe@cs.tu-berlin.de
Intended usage: COMMON.
Author/Change controller:
stewe@cs.tu-berlin.de
IETF Audio/Video transport working group
9.2. SDP Parameters
The MIME media type video/H264 string is mapped to fields in the
Session Description Protocol (SDP) [4] as follows:
o The media name in the "m=" line of SDP MUST be video.
o The encoding name in the "a=rtpmap" line of SDP MUST be H264 (the
MIME subtype).
o The "a=fmtp" line of SDP MUST contain the optional parameters
"profile-level-id", "profile-interoperability", "parameter-sets",
"num-reorder-VCL-NAL-units", and "aggregation-mode", if any, to
indicate the coder capability and configuration, respectively.
These parameters are expressed as a MIME media type string, in
the form of as a semicolon separated list of parameter=value
pairs.
An example of media representation in SDP is as follows (Baseline
Profile, Level 3.0, more than one slice group, arbitrary slice
ordering, and redundant slices are in use):
m=video 49170/2 RTP/AVP 98
a=rtpmap:98 H264/90000
a=fmtp:98 profile-level-id=421E;profile-interoperability=111
10. Security Considerations
So far, no security considerations beyond those of RFC1889 have
been identified.
Currently, the JVT CD does not allow carrying any type of active
payload. However, the inclusion of a "user data" mechanism is
under consideration, which could potentially be used for mechanisms
such as remote software updates of the video decoder and similar
tasks.
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11. Informative Appendix: Application Examples
This payload specification is very flexible in its use, to cover
the extremely wide application space that is anticipated for the
JVT codec. However, such a great flexibility also makes it
difficult for an implementer to decide on a reasonable
packetization scheme. Some information how to apply this
specification to real-world scenarios is likely to appear in the
form of academic publications and a Test Model in the near future.
However, some preliminary usage scenarios should be described here
as well.
11.1. Video Telephony, no Data Partitioning, no packet aggregation
The RTP part of this scheme is implemented and tested (though not
the control-protocol part, see below).
In most real-world video telephony applications, the picture
parameters such as picture size or optional modes never change
during the lifetime of a connection. Hence, all necessary
Parameter Sets (usually only one) are sent as a side effect of the
capability exchange/announcement process e.g. according to the SDP
syntax specified in section 9.2 of this document. Since all
necessary Parameter Set information is established before the RTP
session starts, there is no need for sending any parameter set
NALUs. Data Partitioning is not used either. Hence, the RTP
packet stream consists basically of NALUs that carry single slices
of video information.
The size of those single-slice NALUs is chosen by the encoder such
that they offer the best performance. Often, this is done by
adapting the coded slice size to the MTU size of the IP network.
For small picture sizes this may result in a one-picture-per-one-
packet strategy. The loss of packets and the resulting drift-
related artifacts are cleaned up by Intra refresh algorithms.
11.2. Video Telephony, Interleaved Packetization using Packet
Aggregation
This scheme allows better error concealment and is widely used in
H.263 based designed using RFC2429 packetization. It is also
implemented and good results were reported [8].
The source picture is coded by the VCL such that all MBs of one MB
line are assigned to one slice. All slices with even MB row
addresses are combined into one STAP, and all slices with odd MB
row addresses into another STAP. Those STAPs are transmitted as
RTP packets. The establishment of the Parameter Sets is performed
as discussed above.
Note that the use of STAPs is essential here, because the high
number of individual slices (18 for a CIF picture) would lead to
unacceptably high IP/UDP/RTP header overhead (unless the source
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coding tool FMO is used, which is not assumed in this scenario).
Furthermore, some wireless video transmission systems, such as
H.324M and the IP-based video telephony specified in 3GPP, are
likely to use relatively small transport packet size. For example,
a typical MTU size of H.223 AL3 SDU is around 100 bytes [11].
Coding individual slices according to this packetization scheme
provides a further advantage in communication between wired and
wireless networks, as individual slices are likely to be smaller
than the preferred maximum packet size of wireless systems.
Consequently, a gateway can convert the STAPs used in a wired
network to several RTP packets with only one NALU that are
preferred in a wireless network and vice versa.
11.3. Video Telephony, with Data Partitioning
This scheme is implemented and was shown to offer good performance
especially at higher packet loss rates [8].
Data Partitioning is known to be useful only when some form of
unequal error protection is available. Normally, in single-session
RTP environments, even error characteristics are assumed --
statistically, the packet loss probability of all packets of the
session is the same. However, there are means to reduce the packet
loss probability of individual packets in an RTP session. RFC 2198
[12], for example, allows carrying a redundant copy of a essential
packet in the next RTP packet. Packet-based Forward Error
Correction [13] carried in RFC2198 is also an appropriate means to
protect high priority information.
In all cases, the incurred overhead is substantial, but in the same
order of magnitude as the number of bits that have otherwise be
spent for intra information. However, this mechanism is not adding
any delay to the system.
Again, the complete Parameter Set establishment is performed
through control protocol means.
11.4. Low-Bit-Rate Streaming
This scheme has been implemented with H.263 and gave good results
[14]. There is no technical reason why similarly good results
could not be achievable using the JVT codec.
In today's Internet streaming, some of the offered bit-rates are
relatively low in order to allow terminals with dial-up modems to
access the content. In wired IP networks, relatively large
packets, say 500 - 1500 bytes, are preferred to smaller and more
frequently occurring packets in order to reduce network
congestion. Moreover, use of large packets decreases the amount of
RTP/UDP/IP header overhead. For low-bit-rate video, the use of
large packets means that sometimes up to few pictures should be
encapsulated in one packet.
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However, loss of such a packet would have drastic consequences in
visual quality, as there is practically no other way to conceal a
loss of an entire picture than to repeat the previous one. One way
to construct relatively large packets and maintain possibilities
for successful loss concealment is to construct MTAPs that contain
slices from several pictures in an interleaved manner. An MTAP
should not contain spatially adjacent slices from the same picture
or spatially overlapping slices from any picture. If a packet is
lost, it is likely that a lost slice is surrounded by spatially
adjacent slices of the same picture and spatially corresponding
slices of the temporally previous and succeeding pictures.
Consequently, concealment of the lost slice is likely to succeed
relatively well.
11.5. Robust Packet Scheduling in Video Streaming
This scheme has been implemented with MPEG-4 Part 2 and simulated
in a wireless streaming environment [15]. There is no technical
reason why similar or better results could not be achievable using
the JVT codec.
Streaming clients typically have a receiver buffer that is capable
of storing a relatively large amount of data. Initially, when a
streaming session is established, a client does not start playing
the stream back immediately, but rather it typically buffers the
incoming data for a few seconds. This buffering helps to maintain
continuous playback, because, in case of occasional increased
transmission delays or network throughput drops, the client can
decode and play buffered data. Otherwise, without initial
buffering, the client has to freeze the display, stop decoding, and
wait for incoming data. The buffering is also necessary for either
automatic or selective retransmission in any protocol level. If
any part of a picture is lost, a retransmission mechanism may be
used to resend the lost data. If the retransmitted data is
received before its scheduled decoding or playback time, the loss
is perfectly recovered. Coded pictures can be ranked according to
their importance in the subjective quality of the decoded
sequence. For example, non-reference pictures, such as
conventional B pictures, are subjectively least important, because
their absence does not affect decoding of any other pictures. In
addition to non-reference pictures, the ITU-T H.264 | ISO/IEC
14496-10 standard includes a temporal scalability method called
sub-sequences [16]. Subjective ranking can also be made on data
partition or slice group basis. Coded slices and data partitions
that are subjectively the most important can be sent earlier than
their decoding order indicates, whereas coded slices and data
partitions that are subjectively the least important can be sent
later than their natural coding order indicates. Consequently, any
retransmitted parts of the most important slice and data partitions
are more likely to be received before their scheduled decoding or
playback time compared to the least important slices and data
partitions.
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12. Open Issues
There may be an issue when using the I-D to transport interlace
content. It seems that the draft has a problem when one picture
has more than one timestamp. The authors will try to come to a
conclusion during the Pattaya meeting of JVT (in the week before
the San Francisco IETF), and report in the AVT session whether a
problem exist and, if time permits, present a possible solution.
13. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain
it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works.
However, this document itself may not be modified in any way, such
as by removing the copyright notice or references to the Internet
Society or other Internet organizations, except as needed for the
purpose of developing Internet standards in which case the
procedures for copyrights defined in the Internet Standards process
must be followed, or as required to translate it into languages
other than English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on
an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
14. Intellectual Property Notice
The IETF has been notified of intellectual property rights claimed
in regard to some or all of the specification contained in this
document. For more information consult the online list of claimed
rights at http://www.ietf.org/ipr.
15. References
15.1. Normative References
[1] "Study of Final Committee Draft of Joint Video Specification
(ITU-T Rec. H.264 | ISO/IEC 14496-10 AVC) ", available from
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ftp://ftp.imtc-files.org/jvt-experts/2002_12_Awaji/JVT-
F100.zip, February 2003.
[2] S. Bradner,"Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] H. Schulzrinne, S. Casner, R. Frederick, and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", RFC
1889, January 1996.
[4] M. Handley and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998.
15.2. Informative References
[5] P. Borgwardt, "Handling Interlaced Video in H.26L", VCEG-
N57r2, available from ftp://standard.pictel.com/video-
site/0109_San/VCEG-N57r2.doc, September 2001.
[6] C. Borman et. Al., "RTP Payload Format for the 1998 Version
of ITU-T Rec. H.263 Video (H.263+)", RFC 2429, October 1998.
[7] ISO/IEC IS 14496-2.
[8] S. Wenger, "H.26L over IP", IEEE Transaction on Circuits and
Systems for Video technology, to appear (April 2002).
[9] S. Wenger, "H.26L over IP: The IP Network Adaptation Layer",
Proceedings Packet Video Workshop 02, April 2002, to appear.
[10] T. Stockhammer, M.M. Hannuksela, and S. Wenger, "H.26L/JVT
Coding Network Abstraction Layer and IP-based Transport" in
Proc. ICIP 2002, Rochester, NY, September 2002.
[11] ITU-T Recommendation H.223 (1999).
[12] C. Perkins et. al., "RTP Payload for Redundant Audio Data",
RFC 2198, September 1997.
[13] J. Rosenberg, H. Schulzrinne, "An RTP Payload Format for
Generic Forward Error Correction", RFC 2733, December 1999.
[14] V Varsa, M. Karczewicz, "Slice interleaving in compressed
video packetization", Packet Video Workshop 2000.
[15] S.H. Kang and A. Zakhor, "Packet scheduling algorithm for
wireless video streaming," International Packet Video
Workshop 2002, available http://www.pv2002.org.
[16] M.M. Hannuksela, "Enhanced concept of GOP", JVT-B042,
available ftp://standard.pictel.com/video-site/0201_Gen/JVT-
B042.doc, January 2002.
Author's Addresses
Stephan Wenger Phone: +49-172-300-0813
TU Berlin / Teles AG Email: stewe@cs.tu-berlin.de
Franklinstr. 28-29
D-10587 Berlin
Germany
Thomas Stockhammer Phone: +49-89-28923474
Institute for Communications Eng. Email: stockhammer@ei.tum.de
Munich University of Technology
D-80290 Munich
Germany
Wenger et. al. Expires December 2002 [Page 26]
Internet Draft 01 March, 2003
Miska M. Hannuksela Phone: +358 40 5212845
Nokia Corporation Email: miska.hannuksela@nokia.com
P.O. Box 68
33721 Tampere
Finland
Wenger et. al. Expires December 2002 [Page 27]