how to merge two audios files by the using FFmpeg with special condition?

Question

I have a special issue. Maybe not :D

I have two audios files. First of all. The first audio file has been changed just hear the right side of the headphone. Because of I used that FFmpeg command.

ffmpeg -i fisrt.wav -af “an=stereo|c1=c1” outr.wav

Then, Second audio file has been changed just hear the left side of the headphone. I used this command.

ffmpeg -i second.wav -af “pan=stereo|c0=c0” outl.wav

Problem

I want to merge these files with the special condition. This condition is the first audio/outr.wav/ is just heard the right side of the headphone. Then, second audio/outl.wav/ is just heard the left side of the headphone. So, I tried this command.

ffmpeg -i left.mp3 -i right.mp3 -filter_complex "[0:a][1:a]amerge=inputs=2[a]" -map "[a]" output.wav

Unfortunately, this result is don't want. The result hears both sides of headphone with different volume.

Can you help me, please?!

Solution

Downmix each input into specific output channel

You can do everything in one command using the amerge and pan filters:

ffmpeg -i fisrt.wav -i second.wav -filter_complex "[0][1]amerge=inputs=2,pan=stereo|FL<c0+c1|FR<c2+c3[a]" -map "[a]" output.wav

• This example assumes both inputs are stereo.
• See FFmpeg Wiki: Audio Channels for more info.