RTP Payload Format for BT.656 Video Encoding
RFC 2431
Document | Type |
RFC - Proposed Standard
(October 1998; No errata)
Was draft-tynan-rtp-bt656 (avt WG)
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Author | Dermot Tynan | ||
Last updated | 2013-03-02 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 2431 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group D. Tynan Request for Comments: 2431 Claddagh Films Category: Standards Track October 1998 RTP Payload Format for BT.656 Video Encoding Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (1998). All Rights Reserved. Abstract This document specifies the RTP payload format for encapsulating ITU Recommendation BT.656-3 video streams in the Real-Time Transport Protocol (RTP). Each RTP packet contains all or a portion of one scan line as defined by ITU Recommendation BT.601-5, and includes fragmentation, decoding and positioning information. 1. Introduction This document describes a scheme to packetize uncompressed, studio- quality video streams as defined by BT.656 for transport using RTP [1]. A BT.656 video stream is defined by ITU-R Recommendation BT.656-3 [2], as a means of interconnecting digital television equipment operating on the 525-line or 625-line standards, and complying with the 4:2:2 encoding parameters as defined in ITU-R Recommendation BT.601-5 (formerly CCIR-601) [3], Part A. RTP is defined by the Internet Engineering Task Force (IETF) to provide end-to-end network transport functions suitable for applications transmitting real-time data over multicast or unicast network services. The complete specification of RTP for a particular application requires the RTP protocol document [1], a profile specification document [4], and a payload format specification. This document is intended to serve as the payload format specification for studio-quality video streams. Tynan Standards Track [Page 1] RFC 2431 RTP Payload Format for BT.656 October 1998 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 [5]. 2. Definitions For the purposes of this document, the following definitions apply: Y: An 8-bit or 10-bit coded "luminance" sample. Luminance in this context refers to the BT.601-5 [3] definition which is not the same as a true CIE luminance value. The value of "luminance" refers specifically to video luma. However, in order to avoid confusion with the BT.656 and BT.601 standards, the video luma value is referenced in this document as luminance. Each value has 220 quantization levels with the black level corresponding to level 16 and the peak white level corresponding to 235. Cb, Cr: An 8-bit or 10-bit coded color-difference sample (as per BT.601-5). Each color-difference value has 225 quantization levels in the centre part of the quantization scale with a color-difference of zero having an encoded value of 128. True Black: BT.601-5 defines a true black level as the quad-sample sequence 0x80, 0x10, 0x80, 0x10, representing color-difference values of 128 (0x80) and a luminance value of 16 (0x10). SAV, EAV: Video timing reference codes which appear at the start and end of a BT.656 scan line. 3. Payload Design ITU Recommendation BT.656-3 defines a schema for the digital interconnection of television video signals in conjunction with BT.601-5 which defines the digital representation of the original analog signal. While BT.601-5 refers to images with or without color subsampling, the interconnection standard (BT.656-3) specifically requires 4:2:2 subsampling. This specification also requires 4:2:2 subsampling such that the luminance stream occupies twice the bandwidth of each of the two color-difference streams. For normal 4:3 aspect ratio images, this results in 720 luminance samples per scan line, and 360 samples of each of the two chrominance channels. The total number of samples per scan line in this case is 1440. While this payload format specification can accomodate various image sizes and frame rates, only those in accordance with BT.601-5 are currently supported. Tynan Standards Track [Page 2] RFC 2431 RTP Payload Format for BT.656 October 1998 Due to the lack of any form of video compression within the payload and sampling-rate compliance with BT.601-5, the resultant video stream can be considered "studio quality". However, such a stream can require approximately 20 megabytes per second of network bandwidth. In order to maximize packet size within a given MTU, andShow full document text