I am using the following command to concatenate(append second wav to end of first wav) two audio files (input can be any audio: mp3,wav etc) into one output.mp3 , and it works fine:
ffmpeg -y -i first.wav -i second.wav -filter_complex "[0:0][1:0]concat=n=2:v=0:a=1[out]" -map "[out]" output.mp3
but how can adjust volume for each of input audios separately so my output.mp3 will have two audio files with different volume that i set? for example i want my output contains volume 0.5 for first audio and volume 1 for second audio.be aware that i don't want mix two audio files , Just concatenate two audio files into output with different volume.
Add volume filters before concat.
ffmpeg -y -i first.wav -i second.wav -filter_complex "[0:0]volume=0.5[a0];[1:0]volume=1.0[a1];[a0][a1]concat=n=2:v=0:a=1[out]" -map "[out]" output.mp3