ffmpeg_examples.sh

# strip audio from a video and save as m4a
ffmpeg -i input.mp4 -vn -c:a copy output.m4a

# replace audio track with audio track in identical (m4a) format
ffmpeg.exe -i input_video.mp4 -i replacement_audio.m4a -vcodec copy -acodec copy -map 0:0 -map 1:0 output.mp4

# replace audio, matching file's audio codec (encodes only audio)
ffmpeg.exe -i input_video.mp4 -i replacement_audio.m4a -vcodec copy -map 0:0 -map 1:0 output.mp4