How change audio volumes with amix filter in ffmpeg

Question

I have command to mix two mp3

ffmpeg -i 1.mp3 -i 2.mp3 -filter_complex amix=inputs=2 -c:a libfdk_aac output.mp4 

How to change volume of every audios in result output?

Answer 1

You can add the volume filter:

ffmpeg -i 1.mp3 -i 2.mp3 -filter_complex \
"[0:a]volume=0.5[a0]; \
 [1:a]volume=6dB[a1]; \
 [a0][a1]amix[a]"
-map "[a]" -c:a output.m4a