RTP Payload Format for JPEG-compressed Video
RFC 2435
Document | Type |
RFC - Proposed Standard
(October 1998; No errata)
Obsoletes RFC 2035
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Authors | Paul Stewart , Steven McCanne , Bill Fenner , Lance Berc , Ron Frederick | ||
Last updated | 2020-07-29 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 2435 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group L. Berc Request for Comments: 2435 Digital Equipment Corporation Obsoletes: 2035 W. Fenner Category: Standards Track Xerox PARC R. Frederick Xerox PARC S. McCanne Lawrence Berkeley Laboratory P. Stewart Xerox PARC October 1998 RTP Payload Format for JPEG-compressed Video 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 memo describes the RTP payload format for JPEG video streams. The packet format is optimized for real-time video streams where codec parameters change rarely from frame to frame. This document is a product of the Audio-Video Transport working group within the Internet Engineering Task Force. Comments are solicited and should be addressed to the working group's mailing list at rem- conf@es.net and/or the author(s). Changes from RFC 2035 Most of this memo is identical to RFC 2035. The changes made to the protocol are summarized in Appendix D. Berc, et. al. Standards Track [Page 1] RFC 2435 RTP Payload Format for JPEG October 1998 Key Words 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 [9]. 1. Introduction The Joint Photographic Experts Group (JPEG) standard [1,2,3] defines a family of compression algorithms for continuous-tone, still images. This still image compression standard can be applied to video by compressing each frame of video as an independent still image and transmitting them in series. Video coded in this fashion is often called Motion-JPEG. We first give an overview of JPEG and then describe the specific subset of JPEG that is supported in RTP and the mechanism by which JPEG frames are carried as RTP payloads. The JPEG standard defines four modes of operation: the sequential DCT mode, the progressive DCT mode, the lossless mode, and the hierarchical mode. Depending on the mode, the image is represented in one or more passes. Each pass (called a frame in the JPEG standard) is further broken down into one or more scans. Within each scan, there are one to four components, which represent the three components of a color signal (e.g., "red, green, and blue", or a luminance signal and two chrominance signals). These components can be encoded as separate scans or interleaved into a single scan. Each frame and scan is preceded with a header containing optional definitions for compression parameters like quantization tables and Huffman coding tables. The headers and optional parameters are identified with "markers" and comprise a marker segment; each scan appears as an entropy-coded bit stream within two marker segments. Markers are aligned to byte boundaries and (in general) cannot appear in the entropy-coded segment, allowing scan boundaries to be determined without parsing the bit stream. Compressed data is represented in one of three formats: the interchange format, the abbreviated format, or the table- specification format. The interchange format contains definitions for all the tables used by the entropy-coded segments, while the abbreviated format might omit some assuming they were defined out- of-band or by a "previous" image. The JPEG standard does not define the meaning or format of the components that comprise the image. Attributes like the color space and pixel aspect ratio must be specified out-of-band with respect to Berc, et. al. Standards Track [Page 2] RFC 2435 RTP Payload Format for JPEG October 1998 the JPEG bit stream. The JPEG File Interchange Format (JFIF) [4] is a de-facto standard that provides this extra information using an application marker segment (APP0). Note that a JFIF file is simply a JPEG interchange format image along with the APP0 segment. In theShow full document text