mp4box

MPEG-4 Systems Toolbox: muxe streams into MP4 container. More information: https://gpac.wp.imt.fr/mp4box.

• Display information about an existing MP4 file:

mp4box -info path/to/file

• Add an SRT subtitle file into an MP4 file:

mp4box -add input_subs.srt:lang=eng -add input.mp4 output.mp4

• Combine audio from one file and video from another:

mp4box -add input1.mp4#audio -add input2.mp4#video output.mp4