4.1.4 An IP Transcoding System
The requirement of a transcoding subsystem at the IPTV data center is dependent
on two factors:
(1) The format of the source video content
(2) The compression standard deployed on the IP distribution network
The addition of a transcoding system requires specialized hardware to fulfill
this functionality. These devices are used to convert streams of MPEG-2, uncompressed
Serial Digital Interface (SDI), or even analog material into another
compression format such as H.264/AVC or VC-1. Transcoding does not involve
reconstructing video signals, however, a change in either the bit rate or the resolution of
the incoming video signal does occur. Other functions of transcoders include format
conversion and adjustment of frame rates. Some of themore advanced transcoders also
support encoding and decoding functionality. There are a variety of different methods
of transcodingMPEG-2 content. For example, one method fully decodes the incoming
video stream, processes it when the stream is uncompressed, and then proceeds to
encode into the new compression standard at a lower bit rate.
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