What is the purpose fo demultiplexing and multiplexing?

[easteast]

Just splitting the video and audio?
If there is a problem with audio sync, is it a way to correct the problem by demutiplexing the file and adjust the audio?

[Marco33]

For me, my encoder doesn't like to work with the sound. It gets all humped up. So, I split the file (demultiplex) it. Run the video through my encoder. Then after (multiplex) them back together.

[Heartless Angel]

I've been wondering the same thing. But so far I demux streams if I want to reencode them--resize, change bitrate, etc. I mux, because some authoring progs won't accept seperate streams--for me at least.

"The power of cheese."

[Vejita-sama]

I don't think anyone just de-muxs, then muxs again. There are a lot of reasons to demux:

Several DVD authoring programs will only accept elementary (ie. de-muxed) streams.

Some encoders mux incorrectly resulting in auto padding which can REALLY increase the size of the MPEG (eg. 795MB MPEG but with auto padding -> 825MB).

To replace or edit the original/source audio.

etc. etc.

[easteast]

Is there any program which edits the audio part, like cutting and joining?