On 2022-06-11 03:02 pm, Michael Koch wrote: > I want to concat two audio files. What's wrong with this command line? > > ffmpeg -i birds1.wav -i birds1.wav -lavfi [0][1]concat=n=2:a=1 -c:a > aac -y sound.mp4 Default value for concat v is 1. So you need to set it to 0. concat=n=2:a=1:v=0 Regards, Gyan