Short for multiplex.
It means to combine an audio file and a video file together into a single container format, like AVI or MPEG.
I had to mux the audio and video from that torrent before I could make a DVD.
To speed up editing the video, I de-muxed it and then when I was done, muxed it back together with its audio.
I made a dumb music video by taking the video from Eminem's "Without Me" and muxing it with Katy Perry's "I Kissed a Girl"
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