Many Active PIDs found in 12401 V Transponder...

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A digital TV signal is transmitted as a stream of MPEG-2 data known as a transport stream. Each transport stream has a data rate of up to 40 megabits/second for a cable or satellite network, which is enough for seven or eight separate TV channels, or approximately 25 megabits/second for a terrestrial network.

Each transport stream consists of a set of sub-streams (known as elementary streams), where each elementary stream can contain either MPEG-2 encoded audio, MPEG-2 encoded video, or data encapsulated in an MPEG-2 stream. Each of these elementary streams has a 'packet identifier' (usually known as a PID) that acts as a unique identifier for that stream within the transport stream.

The only restriction on the number of elementary streams in any transport stream is that each elementary stream must have a unique PID value within its containing transport stream

A transport stream consists of a number of audio and video streams that are multiplexed together. First, each service in the transport stream will have its audio and video components encoded using MPEG-2 compression. The result of this process is a set of MPEG-2 elementary streams, each containing one video channel or one (mono or stereo) audio track. These streams are simply a continuous set of video frames or audio data, which is not really suitable for multiplexing. Therefore, we split these streams into packets in order to make the multiplexing process easier. The result of this is a packetized elementary stream, or PES.
 
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