RTP Payload Format of Sun's CellB Video Encoding (RFC2029)
Original Publication Date: 1996-Oct-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
M. Speer: AUTHOR [+1]
This memo describes a packetization scheme for the CellB video encoding. The scheme proposed allows applications to transport CellB video flows over protocols used by RTP. This document is meant for implementors of video applications that want to use RTP and CellB.
Network Working Group M. Speer
Request for Comment: 2029 D. Hoffman
Category: Standards Track Sun Microsystems, Inc.
RTP Payload Format of Sun's CellB 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.
This memo describes a packetization scheme for the CellB video
encoding. The scheme proposed allows applications to transport CellB
video flows over protocols used by RTP. This document is meant for
implementors of video applications that want to use RTP and CellB.
The Cell image compression algorithm is a variable bit-rate video
coding scheme. It provides "high" quality, low bit-rate image
compression at low computational cost. The bytestream that is
produced by the Cell encoder consists of instructional codes and
information about the compressed image.
For futher information on Cell compression technology, refer to .
Currently, there are two versions of the Cell compression technology:
CellA and CellB. CellA is primarily designed for the encoding of
stored video intended for local display, and will not be discussed in
CellB, derived from CellA, has been optimized for network-based video
applications. It is computationally symmetric in both encode and
decode. CellB utilizes a fixed colormap and vector quantization
techniques in the YUV color space to achieve compression.
2. Network Packetization and Encapsulation
2.1 RTP Usage
The RTP timestamp is in units of 90KHz. The same timestamp value is
used for all packet payloads of a frame. The RTP maker bit denotes
the end of a frame.
2.2 CellB Header
The packetization of the CellB bytestream is designed to make the
resulting packet stream robust to packet loss. To achieve this goal,
an additional header is added to each RTP packet to uniquely identify
the location of the first cell of the packet within the current
frame. In addition, the width and height of the frame in pixels is
carried in each CellB packet header. Although the size can only
change between frames, it is carried in every packet to simplify the
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