I want to merge two audio files with defined overlapping time, and the command is by help of this answer:
ffmpeg -i 1.mp3 -i 2.mp3 -filter_complex "adelay=Ns|Ns[a1];[0:a][a1]amix=inputs=2[a]" -map "[a]" output.mp3
The issues are
- the output file size is only ~1/2 original size (quality lost)
- the audio volume before
adepalytimestamp is reduced a lot. Not sure why.
I perceive that it needs decoding when using
-filter_complex, but I'm not sure if it is possible to achieve overlapping without decoding