Cable Modem Theory

by: Rolf V. Østergaard

Downstream Data Formats - Page 10

Downstream data is framed according to the MPEG-TS (transport stream) specification. This is a simple 188/204 byte block format with a single fixed sync byte in front of each block. The Reed-Solomon error correction algorithm reduces the block size from 204 bytes to 188 bytes, leaving 187 for MPEG header and payload.

This is where the various standards differ quite a lot. Some standards even allow various formatting of data within the MPEG-TS payload.

For the DVB/DAVIC standard, the framing inside the MPEG-TS payload is simply a stream of ATM cells.