draft-ietf-avt-smpte292-video-07.txt   draft-ietf-avt-smpte292-video-08.txt 
INTERNET-DRAFT Ladan Gharai INTERNET-DRAFT Ladan Gharai
<draft-ietf-avt-smpte292-video-07.txt> USC/ISI <draft-ietf-avt-smpte292-video-08.txt> USC/ISI
Colin Perkins Colin Perkins
USC/ISI USC/ISI
Gary Goncher Gary Goncher
Tektronix Tektronix
Allison Mankin Allison Mankin
USC/ISI USC/ISI
August 14, 2002 December 2, 2002
RTP Payload Format for SMPTE 292M Video RTP Payload Format for SMPTE 292M Video
<draft-ietf-avt-smpte292-video-07.txt> <draft-ietf-avt-smpte292-video-08.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 2, line 26 skipping to change at page 2, line 26
The use of a dedicated serial interconnect is appropriate in a studio The use of a dedicated serial interconnect is appropriate in a studio
environment, but it is desirable to leverage the widespread availability environment, but it is desirable to leverage the widespread availability
of high bandwidth IP connectivity to allow efficient wide area delivery of high bandwidth IP connectivity to allow efficient wide area delivery
of SMPTE 292M format content. Accordingly, this memo defines an RTP of SMPTE 292M format content. Accordingly, this memo defines an RTP
payload format for SMPTE 292M format video. payload format for SMPTE 292M format video.
It is to be noted that SMPTE 292M streams have a constant high bit rate It is to be noted that SMPTE 292M streams have a constant high bit rate
and are not congestion controlled. Accordingly, use of this payload and are not congestion controlled. Accordingly, use of this payload
format should be tightly controlled and limited to private networks or format should be tightly controlled and limited to private networks or
those networks that provide resource reservation and enhanced quality of those networks that provide resource reservation and enhanced quality of
service. service. This is discussed further in section 9 "Security
Considerations".
This memo only addresses the transfer of uncompressed HDTV. Compressed This memo only addresses the transfer of uncompressed HDTV. Compressed
HDTV is a subset of MPEG-2 [6], which is fully described in document HDTV is a subset of MPEG-2 [9], which is fully described in document
A/53 [7] of the Advanced Television Standards Committee. The ATSC has A/53 [10] of the Advanced Television Standards Committee. The ATSC has
also adopted the MPEG-2 transport system (ISO/IEC 13818-1)[8]. also adopted the MPEG-2 transport system (ISO/IEC 13818-1)[11].
Therefore RFC 2250 [9] sufficiently describes transport for compressed Therefore RFC 2250 [12] sufficiently describes transport for compressed
HDTV over RTP. HDTV over RTP.
2. Overview of SMPTE 292M 2. Overview of SMPTE 292M
A SMPTE 292M television line comprises two interleaved streams, one A SMPTE 292M television line comprises two interleaved streams, one
containing the luminance (Y) samples, the other chrominance (CrCb) containing the luminance (Y) samples, the other chrominance (CrCb)
values. Since chrominance is horizontally sub-sampled (4:2:2 coding) the values. Since chrominance is horizontally sub-sampled (4:2:2 coding) the
lengths of the two streams match (see Figure 3 of SMPTE 292M[1]). In lengths of the two streams match (see Figure 3 of SMPTE 292M[1]). In
addition to being the same length the streams also have identical addition to being the same length the streams also have identical
structures: each stream is divided into four parts, (figure 1): (1) structures: each stream is divided into four parts, (figure 1): (1)
start of active video timing reference (SAV); (2) digital active line; start of active video timing reference (SAV); (2) digital active line;
(3) end of active video timing reference (EAV); and (4) digital line (3) end of active video timing reference (EAV); and (4) digital line
blanking. A SMPTE 292M line may also carry horizontal ancillary data blanking. A SMPTE 292M line may also carry horizontal ancillary data
(H-ANC) or vertical ancillary data (V-ANC) instead of the blanking (H-ANC) or vertical ancillary data (V-ANC) instead of the blanking
level, and likewise, ancillary data may be transported instead of a level, and likewise, ancillary data may be transported instead of a
digital active line. digital active line.
The EAV and SAV are made up of three 10 bit words, with constant values The EAV and SAV are made up of three 10 bit words, with constant values
of 0x3FF 0x000 0x000 and an additional word (designated as XYZ in
of 0x3FF 0x000 0x000 and an additional word (designated as XYZ in
figure 2), carrying a number of flags. This includes an F flag which figure 2), carrying a number of flags. This includes an F flag which
designate which field (1 or 2) the line is transporting and also a V designate which field (1 or 2) the line is transporting and also a V
flag which indicates field blanking. Table 1, further displays the code flag which indicates field blanking. Table 1, further displays the code
values in SAV and EAV. After EAV, are two words LN0 and LN1 (Table 2), values in SAV and EAV. After EAV, are two words LN0 and LN1 (Table 2),
which carry the 11 bit line number for the SMPTE 292M line. The Cyclic which carry the 11 bit line number for the SMPTE 292M line. The Cyclic
Redundancy Check, CRC, is also a two word value, shown as CR0 and CR1 in Redundancy Check, CRC, is also a two word value, shown as CR0 and CR1 in
figure 2. figure 2.
+------------+-----------------------+-----+---------------------+ +------------+-----------------------+-----+---------------------+
| | Digital Line Blanking | | Digital Active Line | | | Digital Line Blanking | | Digital Active Line |
skipping to change at page 4, line 20 skipping to change at page 4, line 20
| LN1 R R R R L10 L9 L8 L7 R R | | LN1 R R R R L10 L9 L8 L7 R R |
+---------------------------------------------------------+ +---------------------------------------------------------+
| NOTES: | | NOTES: |
| LN0 - L10 - line number in binary code. | | LN0 - L10 - line number in binary code. |
| R = reserved, set to "0". | | R = reserved, set to "0". |
+---------------------------------------------------------+ +---------------------------------------------------------+
Table 2: Line number data. Table 2: Line number data.
The number of words and format for active lines and line blanking is The number of words and format for active lines and line blanking is
defined by source format documents. Currently, source video formats defined by source format documents. Currently, source video formats
transfered by SMPTE 292M include SMPTE 260M, 295M, 274M and 296M[2-5]. transfered by SMPTE 292M include SMPTE 260M, 295M, 274M and 296M[5-8].
In this memo we specify how to transfer SMPTE 292M over RTP, In this memo we specify how to transfer SMPTE 292M over RTP,
irrespective of the source format. irrespective of the source format.
3. Conventions Used in this Document 3. Conventions Used in this Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119[10]. document are to be interpreted as described in RFC 2119[2].
4. Payload Design 4. Payload Design
Each SMPTE 292M data line is packetized into one or more RTP packets. Each SMPTE 292M data line is packetized into one or more RTP packets.
This includes all timing signals, blanking levels, active lines and/or This includes all timing signals, blanking levels, active lines and/or
ancillary data. Start of active video (SAV) and end of active video ancillary data. Start of active video (SAV) and end of active video
(EAV+LN+CRC) signals MUST NOT be fragmented across packets, as the SMPTE (EAV+LN+CRC) signals MUST NOT be fragmented across packets, as the SMPTE
292M decoder uses them to detect the start of scan lines. 292M decoder uses them to detect the start of scan lines.
The standard RTP header is followed by a 4 octet payload header. All The standard RTP header is followed by a 4 octet payload header. All
skipping to change at page 5, line 29 skipping to change at page 5, line 27
292M timing signals. This provides more information at the application 292M timing signals. This provides more information at the application
level and adds a level of resiliency, in case the packet containing the level and adds a level of resiliency, in case the packet containing the
EAV is lost. EAV is lost.
The bit length of both timing signals, SAV and EAV+LN+CRC, are multiples The bit length of both timing signals, SAV and EAV+LN+CRC, are multiples
of 8 bits, 40 bits and 80 bits, respectively, and therefore are of 8 bits, 40 bits and 80 bits, respectively, and therefore are
naturally octet aligned. naturally octet aligned.
For the video content it is desirable for the video to both octet align For the video content it is desirable for the video to both octet align
when packetized and also adhere to the principles of application level when packetized and also adhere to the principles of application level
framing, also known as ALF [11]. For YCrCb video, the ALF principle framing, also known as ALF [13]. For YCrCb video, the ALF principle
translates into not fragmenting related luminance and chrominance values translates into not fragmenting related luminance and chrominance values
across packets. For example with the 4:2:0 color subsampling a 4 pixel across packets. For example with the 4:2:0 color subsampling a 4 pixel
group is represented by 6 values, Y1 Y2 Y3 Y4 Cr Cb, and video content group is represented by 6 values, Y1 Y2 Y3 Y4 Cr Cb, and video content
should be packetized such that these values are not fragmented across 2 should be packetized such that these values are not fragmented across 2
packets. However, with 10 bit words this is a 60 bit value which is not packets. However, with 10 bit words this is a 60 bit value which is not
octet aligned. To be both octet aligned, and adhere to ALF, an ALF unit octet aligned. To be both octet aligned, and adhere to ALF, an ALF unit
must represent 2 groups of 4 Pixels, thereby becoming octet aligned on a must represent 2 groups of 4 Pixels, thereby becoming octet aligned on a
15 octet boundary. This length is referred to as the pixel group or 15 octet boundary. This length is referred to as the pixel group or
pgroup, and it is conveyed in the SDP parameters. Table 3 displays the pgroup, and it is conveyed in the SDP parameters. Table 3 displays the
pgroup value for 4:2:2 and 4:4:4 color samplings. Typical source formats pgroup value for various color samplings. Typical source formats use
use 4:2:2 sampling, and require a pgroup of 5 octets, other values are 4:2:2 sampling, and require a pgroup of 5 octets, other values are
included for completeness. included for completeness.
The contents of the Digital Active Line SHOULD NOT be fragmented within The contents of the Digital Active Line SHOULD NOT be fragmented within
a pgroup. A pgroup of 1 indicates that data may be split at any octet a pgroup. A pgroup of 1 indicates that data may be split at any octet
boundary (this is applicable to instances where the source format is not boundary (this is applicable to instances where the source format is not
known). The SAV and EAV+LN+CRC fields MUST NOT be fragmented. known). The SAV and EAV+LN+CRC fields MUST NOT be fragmented.
+-------------------------------------------------------+ +-------------------------------------------------------+
| Color 10 bit | | Color 10 bit |
|Subsampling Pixels words aligned on octet# pgroup| |Subsampling Pixels words aligned on octet# pgroup|
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148351648 MUST be used, and receivers MUST interpret this as 148351648 MUST be used, and receivers MUST interpret this as
148500000/1.001 Hz. 148500000/1.001 Hz.
Optional parameters: pgroup Optional parameters: pgroup
The RECOMMENDED grouping for aligning 10 bit words and octets. The RECOMMENDED grouping for aligning 10 bit words and octets.
Defaults to 1 octet, if not present. Defaults to 1 octet, if not present.
Encoding considerations: SMPTE292M video can be transmitted with Encoding considerations: SMPTE292M video can be transmitted with
RTP as specified in RFC XXXX. RTP as specified in RFC XXXX.
Security considerations: see RFC XXXX section 8. Security considerations: see RFC XXXX section 9.
Interoperability considerations: NONE Interoperability considerations: NONE
Published specification: SMPTE292M Published specification: SMPTE292M
RFC XXXX RFC XXXX
Applications which use this media type: Applications which use this media type:
Video communication. Video communication.
Additional information: None Additional information: None
skipping to change at page 9, line 27 skipping to change at page 9, line 22
Ladan Gharai <ladan@isi.edu> Ladan Gharai <ladan@isi.edu>
IETF AVT working group. IETF AVT working group.
Intended usage: COMMON Intended usage: COMMON
Author/Change controller: Author/Change controller:
Ladan Gharai <ladan@isi.edu> Ladan Gharai <ladan@isi.edu>
8. Mapping to SDP Parameters 8. Mapping to SDP Parameters
Parameters are mapped to SDP [12] as follows: Parameters are mapped to SDP [14] as follows:
m=video 30000 RTP/AVP 111 m=video 30000 RTP/AVP 111
a=rtpmap:111 SMPTE292M/148500000 a=rtpmap:111 SMPTE292M/148500000
a=fmtp:111 pgroup=5 a=fmtp:111 pgroup=5
In this example, a dynamic payload type 111 is used for SMPTE292M. The In this example, a dynamic payload type 111 is used for SMPTE292M. The
RTP timestamp is 148500000 Hz and the SDP parameter pgroup, indicates RTP timestamp is 148500000 Hz and the SDP parameter pgroup, indicates
that for video data after the SAV signal, must be packetized in that for video data after the SAV signal, must be packetized in
multiples of 5 octets. multiples of 5 octets.
9. Security Considerations 9. Security Considerations
RTP packets using the payload format defined in this specification are RTP sessions using the payload format defined in this specification are
subject to the security considerations discussed in the RTP subject to the security considerations discussed in the RTP
specification, and any appropriate RTP profile. This implies that specification [3] and any appropriate RTP profile (e.g. [4]).
confidentiality of the media streams is achieved by encryption.
This payload type does not exhibit any significant non-uniformity in the This payload format does not exhibit any significant non-uniformity in
receiver side computational complexity for packet processing to cause a the receiver side computational complexity for packet processing to
potential denial-of-service threat. cause a potential denial-of-service threat for intended receivers.
It is perhaps to be noted that the bandwidth of this payload is high The bandwidth of this payload format is high enough (1.485 Gbps without
the RTP overhead) to cause potential for denial-of-service if
transmitted onto most currently available Internet paths. Since
congestion control is not possible for SMPTE-292M over RTP flows, use of
the payload SHOULD be narrowly limited to suitably connected network
endpoints, or to networks where QoS guarantees are available.
enough (1.485 Gbps without the RTP overhead) to cause potential for If QoS enhanced service is used, RTP receivers SHOULD monitor packet
denial-of-service if transmitted onto most currently available Internet
paths. Given that congestion control is not possible for SMPTE 292M over loss to ensure that the service that was requested is actually being
RTP flows, use of the payload should be narrowly limited to suitably delivered. If it is not, then they SHOULD assume that they are
connected network endpoints, or to networks where QoS guarantees are receiving best-effort service and behave accordingly.
available, and great care taken with the scope of multicast
transmissions. This potential threat is common to all high bit rate If best-effort service is being used, RTP receivers MUST monitor packet
applications without congestion control. loss to ensure that the packet loss rate is within acceptable parameters
and MUST leave the session is the loss rate is too high. The loss rate
is considered acceptable if a TCP flow across the same network path,
experiencing the same network conditions, would achieve an average
throughput, measured on a reasonable timescale, that is not less than
the RTP flow is achieving. Since congestion control is not possible for
SMPTE-292M flows, this condition can only be satisfied if receivers
leave the session if the loss rate is unacceptably high.
10. Full Copyright Statement 10. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it or others, and derivative works that comment on or otherwise explain it or
assist in its implementation may be prepared, copied, published and assist in its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind, distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are included provided that the above copyright notice and this paragraph are included
skipping to change at page 11, line 22 skipping to change at page 11, line 25
Tektronix, Inc. Tektronix, Inc.
P.O. Box 500, M/S 50-480 P.O. Box 500, M/S 50-480
Beaverton, OR 97077 Beaverton, OR 97077
12. Acknowledgment 12. Acknowledgment
We would like to thank David Richardson for his insightful comments and We would like to thank David Richardson for his insightful comments and
contributions to the draft. We would also like to thank Chuck Harrison contributions to the draft. We would also like to thank Chuck Harrison
for his input and for explaining the intricacies of SMPTE 292M. for his input and for explaining the intricacies of SMPTE 292M.
13. Bibliography 13. Normative References
[1] Society of Motion Picture and Television Engineers, [1] Society of Motion Picture and Television Engineers,
Bit-Serial Digital Interface for High-Definition Television Bit-Serial Digital Interface for High-Definition Television
Systems, SMPTE 292M-1998. Systems, SMPTE 292M-1998.
[2] Society of Motion Picture and Television Engineers, [2] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119.
[3] H. Schulzrinne, S. Casner, R. Frederick and V. Jacobson, "RTP: A
Transport Protocol for Real-Time Applications", IETF, Work in
Progress (draft-ietf-avt-rtp-new-11.txt)
[4] H. Schulzrinee and S. Casner, "RTP Profile for Audio and Video
Conferences with Minimal Control", IETF, Work in progress,
(draft-ietf-avt-profile-new-12.txt).
14. Informative References
[5] Society of Motion Picture and Television Engineers,
Digital Representation and Bit-Parallel Interface - 1125/60 Digital Representation and Bit-Parallel Interface - 1125/60
High-Definition Production System, SMPTE 260M-1999. High-Definition Production System, SMPTE 260M-1999.
[3] Society of Motion Picture and Television Engineers, [6] Society of Motion Picture and Television Engineers,
1920x1080 50Hz, Scanning and Interface, SMPTE 295M-1997. 1920x1080 50Hz, Scanning and Interface, SMPTE 295M-1997.
[4] Society of Motion Picture and Television Engineers, [7] Society of Motion Picture and Television Engineers,
1920x1080 Scanning and Analog and Parallel Digital Interfaces 1920x1080 Scanning and Analog and Parallel Digital Interfaces
for Multiple Picture Rates, SMPTE 274M-1998. for Multiple Picture Rates, SMPTE 274M-1998.
[5] Society of Motion Picture and Television Engineers, [8] Society of Motion Picture and Television Engineers,
1280x720 Scanning, Analog and Digital Representation and Analog 1280x720 Scanning, Analog and Digital Representation and Analog
Interfaces, SMPTE 296M-1998. Interfaces, SMPTE 296M-1998.
[6] ISO/IEC International Standard 13818-2; "Generic coding of [9] ISO/IEC International Standard 13818-2; "Generic coding of
moving pictures and associated audio information: Video", 1996. moving pictures and associated audio information: Video", 1996.
[7] ATSC Digital Television Standard Document A/53, September 1995, [10] ATSC Digital Television Standard Document A/53, September 1995,
http://www.atsc.org http://www.atsc.org
[8] ISO/IEC International Standard 13818-1; "Generic coding of [11] ISO/IEC International Standard 13818-1; "Generic coding of
moving pictures and associated audio information: Systems",1996. moving pictures and associated audio information: Systems",1996.
[9] Hoffman, Fernando, Goyal, Civanlar, "RTP Payload Format for [12] Hoffman, Fernando, Goyal, Civanlar, "RTP Payload Format for
MPEG1/MPEG2 Video", RFC 2250, IETF, January 1998. MPEG1/MPEG2 Video", RFC 2250, IETF, January 1998.
[10] S. Bradner, "Key words for use in RFCs to Indicate [13] Clark, D. D., and Tennenhouse, D. L., "Architectural Considerations
Requirement Levels", RFC 2119.
[11] Clark, D. D., and Tennenhouse, D. L., "Architectural Considerations
for a New Generation of Protocols", In Proceedings of SIGCOMM '90 for a New Generation of Protocols", In Proceedings of SIGCOMM '90
(Philadelphia, PA, Sept. 1990), ACM. (Philadelphia, PA, Sept. 1990), ACM.
[12] M. Handley and V. Jacobson, "SDP: Session Description Protocol", [14] M. Handley and V. Jacobson, "SDP: Session Description Protocol",
RFC 2327, April 1998. RFC 2327, April 1998.
 End of changes. 

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