Originally Posted by nyctveng
a lot of content providers have been changing from mpeg2 to 4 as the technology matures and equipment prices come down. they save money or stuff twice as much content on uplink transponder. ESPN has been the most high profile and big changovers. the re-encoding that everyone calls it is actually called transcoding and is done by the IRD. so whether u have comcast or fios, they are both using the same type IRD that ESPN or whoever provide to receive and transcode content.
It doesn't matter if you call it re-encoding or transcoding, because in all fielded products it's the same thing. All of the "transcoders" out there decode all the way to baseband and then encode the uncompressed YCbCr data just like any other encoder.
In the early days of H.264 deployment, there were folks trying to create transcoders that attempted to reuse the information (like motion vectors) in the original bitstream to avoid a complete decode and encode. None of these schemes were able to compete with a complete decode and encode architecture quality wise, and have now all been abandoned.
The Motorola DSR-6100 IRD that ESPN uses for their downlink customers contains an encoder that is almost identical to the Motorola SE-3000 encoder that FOX uses for their network uplink.