RFC 2029 (rfc2029) - Page 2 of 6
RTP Payload Format of Sun's CellB Video Encoding
Alternative Format: Original Text Document
RFC 2029 RTP Payload Format October 1996
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
packet encoding.
0 1 2 3
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cell X Location | Cell Y Location |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Width of Image | Height of Image |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| Compressed CellB Data |
| .... |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
All fields are 16-bit unsigned integers in network byte order, and
are placed at the beginning of the payload for each RTP packet. The
Cell X and the Cell Y Location coordinates are expressed as cell
coordinates, not pixel coordinates. Since cells represent 4x4 blocks
of pixels, the X or Y dimension of the cell coordinates range in
value from 0 through 1/4 of the of the same dimension in pixel
coordinates.
2.3 Packetization Rules
A packet can be of any size chosen by the implementor, up to a full
frame. All multi-byte codes must be completely contained within a
packet. In general, the implementor should avoid packet sizes that
result in fragmentation by the network.
Speer & Hoffman Standards Track