One document matched: draft-kristensen-avt-rtp-h264-params-00.txt
Audio/Video Transport WG T. Kristensen, Ed.
Internet-Draft TANDBERG
Updates: 3984 (if approved) R. Even
Intended status: Standards Track Polycom
Expires: December 21, 2007 June 19, 2007
Parameters for Static Macroblocks and Aspect Ratio in the RTP Payload
Format for H.264 Video
draft-kristensen-avt-rtp-h264-params-00
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
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 working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on December 21, 2007.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document updates RFC 3984. It defines new optional parameters
addressing new extensions currently supported in H.323 systems: The
signalling of the maximum rate of static macroblocks a decoder is
able to process. The signalling of the sample aspect ratio supported
by the sender or the receiver.
Kristensen & Even Expires December 21, 2007 [Page 1]
Internet-Draft New H.264 RTP parameters June 2007
Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction and Overview . . . . . . . . . . . . . . . . . . . 3
2.1. Static macroblocks . . . . . . . . . . . . . . . . . . . . 3
2.2. Sample aspect ratio . . . . . . . . . . . . . . . . . . . . 3
3. Payload Format Parameters . . . . . . . . . . . . . . . . . . . 4
3.1. Media Type Registration . . . . . . . . . . . . . . . . . . 4
4. SDP Parameters . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Mapping of the optional parameters to SDP . . . . . . . . . 5
4.2. Usage with SDP offer/answer . . . . . . . . . . . . . . . . 5
4.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 8
Kristensen & Even Expires December 21, 2007 [Page 2]
Internet-Draft New H.264 RTP parameters June 2007
1. Requirements notation
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 [1].
2. Introduction and Overview
ITU-T H.264 [4] codec and ITU-T H.241 [5], the extended video video
procedures and control signals for H.300 series terminals, continue
to evolve. The IETF RTP payload formats and parameters need to be
updated to include important new functionalities not covered in RFC
3984 [3]. This document describes new parameters used to signal
maximal number of static macroblocks per second and the sample aspect
ratio of the H.264 video stream.
The new parameters are already defined in the latest version of H.241
[5]. This proposal defines media type parameters for them and allows
their use in SDP based systems.
2.1. Static macroblocks
Running H.264 encode and decode operations require large amounts of
video processing power. The challenge being to sustain high
framerate (e.g. 30 frames/sec) with the large framesizes that stems
from recent demand for HD resolution. In practice, a certain amount
of macroblocks in the video stream, which do not change in a frame,
can be defined as static and, this way, free up additional processing
cycles for the handling of non-static macroblocks.
Based on a given amount of video processing resources and a given
framerate, a higher number of static macroblocks enables a
correspondingly higher resolution. A new parameter MaxStaticMBPS
(maximum static macroblocks per second) was introduced in H.241 to
address this issue. The MaxStaticMBPS parameter is specified in
Section 8.3.2.8 of H.241 [5].
2.2. Sample aspect ratio
Sample Aspect Ratio (SAR) is the ratio between the intended
horizontal distance between the columns and the intended vertical
distance between the rows of the luma sample array in a frame.
Sample aspect ratio is expressed as h:v, where h is horizontal width
and v is vertical height (in arbitrary units of spatial distance). A
sample is an individual luma picture element ("pixel") making up the
complete displayed image (including both fields in the case of
interlaced-scan video). For example, the sample aspect ratio for a
Kristensen & Even Expires December 21, 2007 [Page 3]
Internet-Draft New H.264 RTP parameters June 2007
CIF picture is 12:11.
All systems which send H.264 video should indicate the sample aspect
ratio in the VUI parameters specified in Annex E of H.264 [4].
In the absence of a H.264 VUI parameter aspect_ratio_idc value in the
received H.264 bitstream, and in the case of an aspect_ratio_idc
value equal to 0, the sample aspect ratio may be assumed to have a
value according to Table 1b in H.241 [5].
This draft enables the receiver to indicate what sample aspect ratio
it can support without distortion. This may help an encoder to
support the different monitors being used today, which support
different aspect ratios such as 4:3 and 16:9.
3. Payload Format Parameters
The optional H264 media subtype parameters max-smbps, sar and esar
specified below comes in addition to the list of optional H264 media
subtype parameters defined in Section 8.1 of RFC 3984 [3].
3.1. Media Type Registration
New optional parameters:
max-smbps: The value of max-smbps is an integer indicating the
maximum static macroblock processing rate in units of static
macroblocks per second, under the hypothetical assumption that all
macroblocks are static macroblocks. When max-smbps is signalled
the MaxMBPS value in Table A-1 of H.264 [4] should be replaced
with the result of the following computation:
1. If the parameter max-mbps is signalled, set a variable
MaxMacroblocksPerSecond to the value of max-mbps. Otherwise,
set MaxMacroblocksPerSecond equal to the value of MaxMBPS for
the level in Table A-1 of H.264 [4].
2. Set a variable P_non-static to the proportion of non-static
macroblocks in picture n.
3. Set a variable P_static to the proportion of static
macroblocks in picture n.
Kristensen & Even Expires December 21, 2007 [Page 4]
Internet-Draft New H.264 RTP parameters June 2007
4. The value of MaxMBPS in Table A-1 of H.264 [4] should be
considered by the encoder to be equal to:
1
-----------------------------------------
P_non-static P_static
------------------------- + -----------
MaxMacroblocksPerSecond max-smbps
The encoder should recompute this value for each picture.
The value of max-smbps MUST be greater than the value of MaxMBPS
for the level given in Table A-1 of H.264 [4]. Senders MAY use
this knowledge to send pictures of a given size at a higher
picture rate than is indicated in the signalled level.
sar: The value of this parameter is an integer that indicates
support of sample aspect ratios corresponding to H.264
aspect_ratio_idc values in the range from 1 to N inclusive, where
N is the value of this parameter (see Table E-1 of H.264 [4]).
esar: The value of this parameter is 1 or 0. 1 indicates support for
all sample aspect ratios which are expressible using the H.264
aspect_ratio_idc value of 255 (Extended_SAR, see Table E-1 of
H.264 [4]). If the parameter does not exist, its value is 0.
4. SDP Parameters
4.1. Mapping of the optional parameters to SDP
The optional parameters max-smbps, sar and esar 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
paremeter=value pairs.
4.2. Usage with SDP offer/answer
When H.264 is offered over RTP using SDP in an Offer/Anwer model [2]
for negotiation of unicast streams, the following limitations and
rules applies:
The optional parameter max-smbps is treated the same way as max-mbps,
when used in both the SDP Offer/Answer model [2] and declarative
session descriptions. Its interpretation depends on the direction
attribute. When the direction attribute is sendonly, then the
parameters describe the limits of the RTP packets and the NAL unit
stream that the sender is capable of producing. When the direction
Kristensen & Even Expires December 21, 2007 [Page 5]
Internet-Draft New H.264 RTP parameters June 2007
attribute is sendrecv or recvonly, the parameters describe the
limitations of what the receiver accepts. The profile-level-id
parameter MUST be present in the same receiver capability description
that contains this parameter.
The interpretation of the optional parameter sar depends on the
direction attribute. When the direction attribute is sendonly, then
it indicates the range of sample aspect ratios the stream will
contain. When the direction attribute is sendrecv or recvonly, the
value of this parameter indicates the range of sample ratios that the
receiver is able to display without geometric (shape) distortion.
The receiver will still be able to display any other sample aspect
ratio with distortion.
H.264 compliant encoders may not be able to scale a picture, in this
case the basic rule is that terminals which display received video
shall be capable of displaying any picture format and frame rate for
which they signal the capability. The format used to display such
received video streams is not required to match the exact format
transmitted.
The optional parameter esar is a receiver capability that permits a
terminal to signal additional abilities to display any decoded video
expressible using the H.264 aspect_ratio_idc value of 255
(Extended_SAR, see Table E-1 of H.264 [4]). The actual extended
aspect ratio is conveyed using H.264 VUI.
4.3. Examples
TBD
5. IANA Considerations
This draft updates RFC 3984 by adding three new optional parameters
to the H264 media subtype. The parameters are specified in Section
Section 3 of this document.
6. Security Considerations
No separate considerations introduced in this document. Refer to
section 9 of RFC 3984 [3].
7. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Kristensen & Even Expires December 21, 2007 [Page 6]
Internet-Draft New H.264 RTP parameters June 2007
Levels", BCP 14, RFC 2119, March 1997.
[2] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
Session Description Protocol (SDP)", RFC 3264, June 2002.
[3] Wenger, S., Hannuksela, M., Stockhammer, T., Westerlund, M., and
D. Singer, "RTP Payload Format for H.264 Video", RFC 3984,
February 2005.
[4] International Telecommunications Union, "Advanced video coding
for generic audiovisual services", ITU-T Recommendation H.264,
March 2005.
[5] International Telecommunications Union, "Extended video
procedures and control signals for H.300-series terminals", ITU-
T Recommendation H.241, May 2006.
Authors' Addresses
Tom Kristensen (editor)
TANDBERG
Philip Pedersens vei 22
N-1366 Lysaker
Norway
Phone: +47 67125125
Email: tom.kristensen@tandberg.com, tomkri@ifi.uio.no
URI: http://www.tandberg.com
Roni Even
Polycom
94 Derech Em Hamoshavot
Petach Tikva 49130
Israel
Email: roni.even@polycom.co.il
URI: http://www.polycom.com
Kristensen & Even Expires December 21, 2007 [Page 7]
Internet-Draft New H.264 RTP parameters June 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
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.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Kristensen & Even Expires December 21, 2007 [Page 8]
| PAFTECH AB 2003-2026 | 2026-04-23 12:07:24 |