Statistical multiplexer
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A Statistical multiplexer (or stat-mux) is a device which allows broadcasters to change the bitrate of channels according to needs of different channels at different times.
Different types of images require different amounts of bandwidth to produce a good quality image. Programs with very little movement, such as a news broadcast, require much less bandwidth than programs that contain rapidly-moving images, such as hockey game.
If a broadcaster is showing news on one channel and ice hockey on another channel, with fixed multiplexing each channel has, say, 2 Mbit/s. The channel with the news show would have good image quality at this bitrate, because news shows have little movement and require little bandwidth. However, the channel showing the hockey game would suffer poorer image quality, because transmitting clear moving images of fast movement and crowd shots require large bandwidth.
A statistical multiplexer allows the broadcaster to allocate bandwidth to wherever it is needed. Thus 0.5 Mbit/s are allocated to the channel with the news program and 3.5 Mbit/s to the channel with the hockey game. This results in a good quality picture for both channels.
