How to create multi audio for a mp4 file?

[triumph2004]

I have a lot of mp4 files that I would like to add a second audio track/channel onto them. Can someone help to guide me on how to do this? Thanks so much.

[pandy]

http://stackoverflow.com/questions/11779490/how-to-add-a-new-audio-not-mixing-into-a-v...83474#11783474

[Krispy Kritter]

If you can use mkv instead of mp4, you can simply drop the two files into MKVToolNix.

[triumph2004]

Thanks so much. After researching, I figured it out using ffmpeg:

ffmpeg -i input.mp4 -i input.mp3 -map 0:v -map 0:a:0 -map 1:a -codec copy output.mp4

[pandy]

Thanks so much. After researching, I figured it out using ffmpeg:

ffmpeg -i input.mp4 -i input.mp3 -map 0:v -map 0:a:0 -map 1:a -codec copy output.mp4

Bingo!