What is decoder ? n what is demultiplexure?

Question

What is decoder ? n what is demultiplexure?

Answer 1

Decoders and demutiplexers are the opposite of encoders and multiplexers.  There are many uses for decoders and demultiplexers, however since you asked in this section I'll use a video example.

When we build a digital stream, we must take the video and audio and "encode" it.  The encoder will turn the video and audio into digital, if it isn't already, and then will cut it into "packets" of data and label each one with a "packet ID" or PID.  If we are building sub channels, (like 60.1, 60.2 etc on your DTV) we will have a separate encoder for each stream.

The encoded (packetized) video is then sent to a multiplexer (or mux).  The mux will take the encoded video(s) and weave them together into one stream.  This is what we use to "transport" the video to your home.

Inside the TV receiver, we must first "demux" the stream to get the individual encoded video streams back.  This is the job of the demultiplexer.

Then the receiver can pick out the individual video stream and decode it to recover the original video and audio.

This is an oversimplified explanation and there is a bit more stuff going on in the process, but I'm sure you get the idea.

I hope this helps.

Answer 2

An inverse multiplexer or demultiplexer (often abbreviated to "inverse mux", "imux" or "demux") allows a data stream to be broken into multiple lower data rate communications links. Note that this is the reverse of a multiplexor.  An example is the reception of telemetry from the computer/instrumentation system of a satellite, space craft or other remote vehicle.

Decoder:  A device that decodes a scrambled electronic signal e.g. of a satellite television signal.

Encoder:  A device used to encode a signal either for cryptography or compression.

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