FFmpeg
From Leo's Notes
This page was last edited on 29 March 2015, at 19:23.
Merging mp4 and m4a
Using ffmpeg you can combine the two together:
command: ffmpeg -i video.mp4 -i audio.m4a -acodec copy -vcodec copy output.mp4
Issues
Copying DASH video (via -vcodec copy) using versions older than 0.10 will result in an empty file because it is unable to read the video contents.