draft-ietf-avt-uncomp-video-ext-00.txt		draft-ietf-avt-uncomp-video-ext-01.txt
	Network Working Group C. Perkins		Network Working Group C. Perkins
	Internet-Draft University of Glasgow		Internet-Draft University of Glasgow
	Expires: March 6, 2006 September 2, 2005		Updates: 4175 (if approved) September 25, 2005
			Expires: March 29, 2006
	RTP Payload Format for Uncompressed Video: Additional Colour Sampling		RTP Payload Format for Uncompressed Video: Additional Colour Sampling
	Modes		Modes
	draft-ietf-avt-uncomp-video-ext-00.txt		draft-ietf-avt-uncomp-video-ext-01.txt
	Status of this Memo		Status of this Memo
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	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2005).		Copyright (C) The Internet Society (2005).
	Abstract		Abstract
	This memo extends the RTP Payload Format for Uncompressed Video to		This memo extends the RTP Payload Format for Uncompressed Video to
	support additional RGB sampling modes.		support additional colour sampling modes.
	1. Introduction		1. Introduction
	The RTP Payload Format for Uncompressed Video [1] defines a scheme to		The RTP Payload Format for Uncompressed Video [1] defines a scheme to
	packetise uncompressed, studio-quality, video streams for transport		packetise uncompressed, studio-quality, video streams for transport
	using RTP [2]. A range of standard and high definition video formats		using RTP [2]. A range of standard and high definition video formats
	are supported, and parameters are defined so sender and receiver can		are supported, and parameters are defined so sender and receiver can
	signal the image size, colour space, pixel depth, etc.		negotiate the image size, colour space, pixel depth, and colour
			sampling mode.
	A limitation of the format is that the number of bits per sample is		A limitation of the signalling is that the number of bits per sample
	signalled as being the same for each colour component. For example,		is assumed to be the same for each colour component. For example, it
	it is not possible to signal transport of RGB format video using 5		is possible to signal video using RGB colour sampling with 8-bits for
	bits each for the Red and Blue components and 6 bits for the Green,		each of the Red, Green and Blue components (24 bits per pixel), but
	packing one pixel into two octets. Such video formats can easily be		not video using RGB colour sampling with 5-bits each for the Red and
	supported in the payload format, but cannot be signalled using the		Blue components, but 6-bits for the Green component (16 bits per
	parameters defined. This memo extends [1] with additional colour		pixel). Such video formats can easily be transported by the payload
	sampling modes, to signal such video formats.		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		2. 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 [3].		document are to be interpreted as described in RFC 2119 [3].
	3. Payload Format Parameters		3. Payload Format Parameters
	This memo defines six new colour sampling modes that MAY be signalled		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+",		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		"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,		of samples as do the RGB and BGR colour sampling modes respectively
	except that an additional bit of colour depth is available for the		([1] Section 4.3), except that an additional bit per sample of colour
	component marked by the + symbol (i.e. when "depth=N" is signalled, N		depth MUST be used for the component marked by the + symbol. The
	bits are allocated to unmarked components, but N+1 bits MUST be		mandatory parameter "depth=N" indicates that N bits per sample are
	allocated to the marked component). All other features of the		used by the unmarked components, but N+1 bits are used by the marked
	payload format remain as defined in [1].		component. All other features of the payload format are as defined
			in [1].
	The primary use of these colour sampling modes is to enable efficient		The primary use of these colour sampling modes is to enable efficient
	packing of data into small pixel groups ("pgroups"). The most common		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		use case is expected to be video with "depth=5", where the additional
	additional bit of colour depth enables a single pixel to fit into two		bit of colour depth for the marked component enables a single pixel
	octets without padding. The new colour sampling modes MAY be used		to fit into two octets without padding. The new colour sampling
	for other depths, however, should that prove useful.		modes MAY be used for other depths, however, should that prove
			useful.
	4. Example		4. Example
	A common uncompressed video format is RGB with 5 bits for the Red and		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		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,		16 bits per pixel. Using the sampling modes defined in this memo,
	this can be signalled in SDP according to the following example:		this can be signalled in SDP according to the following example:
	v=0		v=0
	o=jdoe 2890844526 2890842807 IN IP4 10.47.16.5		o=jdoe 2890844526 2890842807 IN IP4 10.47.16.5
	s=-		s=-
	c=IN IP4 10.47.16.6		c=IN IP4 10.47.16.6
	t=2873397496 2873404696		t=2873397496 2873404696
	a=recvonly
	m=video 51372 RTP/AVP 99		m=video 51372 RTP/AVP 99
	a=rtpmap:99 raw/90000		a=rtpmap:99 raw/90000
	a=fmtp:99 sampling=RG+B; width=1024; height=768; depth=5;		a=fmtp:99 sampling=RG+B; width=1024; height=768; depth=5;
	colorimetry=SMPTE240M		colorimetry=SMPTE240M
	(some of the lines in have been wrapped due to formatting constraints		The last line has been wrapped due to formatting constraints of this
	on this memo).		memo, and forms one complete line in the SDP file.
	5. Security Considerations		5. Security Considerations
	The security considerations of [1] apply. No additional security		The security considerations of [1] apply. No additional security
	considerations are introduced by support for new colour sampling		considerations are introduced by support for new colour sampling
	modes.		modes.
	6. IANA Considerations		6. IANA Considerations
	The video/raw media type is extended with six new values for the		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		"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		[1]. The new values are "RGB+", "RG+B", "R+GB", "BGR+", "BG+R" and
	"B+GR" as described in this memo.		"B+GR" as described in this memo.
	7. Acknowledgements		7. Acknowledgements
	Thanks to Jeremy Searle and Andrew Lee.		Thanks to Jeremy Searle and Andrew Lee at Westland Helicopters.
	8. Normative References		8. Normative References
	[1] Gharai, L. and C. Perkins, "RTP Payload Format for Uncompressed		[1] Perkins, C. and L. Gharai, "RTP Payload Format for Uncompressed
	Video", draft-ietf-avt-uncomp-video-06 (work in progress),		Video", RFC 4175, September 2005.
	February 2004.
	[2] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,		[2] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
	"RTP: A Transport Protocol for Real-Time Applications", STD 64,		"RTP: A Transport Protocol for Real-Time Applications", STD 64,
	RFC 3550, July 2003.		RFC 3550, July 2003.
	[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement		[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
	Levels", BCP 14, RFC 2119, March 1997.		Levels", BCP 14, RFC 2119, March 1997.
	Author's Address		Author's Address
End of changes. 12 change blocks.
	30 lines changed or deleted		34 lines changed or added
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