You remove audio by using the
-an flag.ffmpeg -i example.mkv -c copy -an example-nosound.mkv
Full ffmpeg documentation here.
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add audio to video file
ffmpeg -i pk4.mp4 -i toutput.m4a -map 0 -map 1 -codec copy pk8.mp4
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merger 2 audio file
ffmpeg -i tabrakmasuk.m4a -i tabrakmasuk2.m4a -filter_complex "[0:a][1:a]concat=n=2:v=0:a=1" toutput.m4a
ffmpeg -i tabrakmasuk.m4a -i tabrakmasuk2.m4a -filter_complex "[0:a][1:a]concat=n=2:v=0:a=1" toutput.m4a
