Network Working Group C. Perkins Internet-Draft University of Glasgow Expires: January 11, 2006 July 10, 2005 RTP Payload Format for Uncompressed Video: Additional Colour Sampling Modes draft-perkins-avt-uncomp-video-ext-00.txt 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 January 11, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This memo extends the RTP Payload Format for Uncompressed Video to support additional RGB sampling modes. 1. Introduction The RTP Payload Format for Uncompressed Video [1] defines a scheme to packetise uncompressed, studio-quality, video streams for transport using RTP [2]. A range of standard and high definition video formats Perkins Expires January 11, 2006 [Page 1]
Internet-Draft Uncompressed Video Extensions July 2005 are supported, and parameters are defined so sender and receiver can signal the image size, colour space, pixel depth, etc. A limitation of the format is that the number of bits per sample is signalled as being the same for each colour component. For example, it is not possible to signal transport of RGB format video using 5 bits each for the Red and Blue components and 6 bits for the Green, packing one pixel into two octets. Such video formats can easily be supported in the payload format, but cannot be signalled using the parameters defined. This memo extends [1] with additional colour sampling modes, to signal such video formats. 2. Conventions Used in this Document 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 [3]. 3. Payload Format Parameters This memo defines six new colour sampling modes that MAY be signalled for use with [1]. The new modes are "RGB+", "RG+B", "R+GB", "BGR+", "BG+R" and "B+GR". These sampling modes use the same packing order of samples as do the RGB and BGR colour sampling modes respectively, except that an additional bit of colour depth is available for the component marked by the + symbol (i.e. when "depth=N" is signalled, N bits are allocated to unmarked components, but N+1 bits MUST be allocated to the marked component). All other features of the payload format remain as defined in [1]. The primary use of these colour sampling modes is to enable efficient packing of data into small pixel groups ("pgroups"). The most common use case is expected to be video with five bits per sample, where the additional bit of colour depth enables a single pixel to fit into two octets without padding. The new colour sampling modes MAY be used for other depths, however, should that prove useful. 4. Example A common uncompressed video format is RGB with 5 bits for the Red and Blue components and six bits for the Green component, for a total of 16 bits per pixel. Using the sampling modes defined in this memo, this can be signalled in SDP according to the following example: Perkins Expires January 11, 2006 [Page 2]
Internet-Draft Uncompressed Video Extensions July 2005 v=0 o=jdoe 2890844526 2890842807 IN IP4 10.47.16.5 s=- c=IN IP4 10.47.16.6 t=2873397496 2873404696 a=recvonly m=video 51372 RTP/AVP 99 a=rtpmap:99 raw/90000 a=fmtp:99 sampling=RG+B; width=1024; height=768; depth=5; colorimetry=SMPTE240M (some of the lines in have been wrapped due to formatting constraints on this memo). 5. Security Considerations The security considerations of [1] apply. No additional security considerations are introduced by support for new colour sampling modes. 6. IANA Considerations The video/raw media type is extended with six new values for the "sampling" parameter according to the rules defined in section 6.2 of [1]. The new values are "RGB+", "RG+B", "R+GB", "BGR+", "BG+R" and "B+GR" as described in this memo. 7. Acknowledgements Thanks to Jeremy Searle and Andrew Lee. 8. Normative References [1] Gharai, L. and C. Perkins, "RTP Payload Format for Uncompressed Video", draft-ietf-avt-uncomp-video-06 (work in progress), February 2004. [2] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Perkins Expires January 11, 2006 [Page 3]
Internet-Draft Uncompressed Video Extensions July 2005 Author's Address Colin Perkins University of Glasgow Department of Computing Science 17 Lilybank Gardens Glasgow G12 8QQ UK Email: csp@csperkins.org Perkins Expires January 11, 2006 [Page 4]
Internet-Draft Uncompressed Video Extensions July 2005 Intellectual Property Statement 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. Disclaimer of Validity 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 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. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Perkins Expires January 11, 2006 [Page 5]