``` //ffmpeg -y -i inputbg.mp4 -i input.mp3 -t 48 -filter_complex "[0:a]volume=1.0[a1];[1:a]volume=0.0[a2]; [a2][a1]amix=inputs=2:duration=first[aout]" -map "[aout]" -c:v copy -map 0:v:0 input.mp4 ```