How do I mux mp4 video and mp3 audio?

How do I mux mp4 video and mp3 audio into a single file. MP4box crashes when I try to add a mp3 audio stream.

mp4box shouldnt crash. can you upload a small sample of this mp3 somewhere showing the problem moved

Make sure your MP4 video file is the first file added, then add the MP3 audio file. If you are using the command line, your command should look something like: MP4Box.exe -add "video.mp4" -add "audio.mp3" -out "output file.mp4" If you get it backwards and add the MP3 audio file first it doesn't work (at least for me).