I have 3 mp4 files:
- 1.mp4 - Has video, no audio
- 2.mp4 - Has video and audio
- 3.mp4 - Has video and audio
I have created a clips file (clips.txt) for concatenation:
file '1.mp4' file '2.mp4' file '3.mp4'
I run the following command line:
ffmpeg -f concat -i "clips.txt" -c:a aac -b:a 160k -y "out.mp4"
The file that is produced has video but no audio, presumably because 1.mp4 has no audio track.
If I rearrange clips.txt so 1.mp4 is not first, out.mp4 has an audio track.
Is there a way of forcing ffmpeg to use audio? I guess it would have to produce a silent audio track for any silent videos.