two other cool things you can do with ffmpeg in your pipeline.
first, you can automatically take mono audio and convert to stereo. this is necessary in my case because I have a Speedcom communicator wired permanently in my car, which plugs into the GoPro but is a mono source. Audio sounds much stronger and cleaner when it's stereo of course. ffmpeg will fix it for you automatically in seconds.
second, you can manipulate the volume in the base track. if my mic was out of position or for some reason the audio was just poor even after doing the stereo conversion, I'll add a parameter to ffmeg to fix it.
this command will take a mono channel on the left side (e.g. the "FL" below) and convert to stereo, while increasing volume by 3dB.
ffmpeg -i "<INPUT_VIDEO>.MP4" -map 0 -c:v copy -c:a aac -ac 2 -af "pan=stereo| c0=FL | c1=FL, volume=3dB" -map -0:2 -map -0:3 "<INPUT_VIDEO>-Stereo3dB.MP4"
This command runs super fast because ffmpeg just literally copies the video track - there's no manipulation of that at all which is what normally burns up time doing post processing. In this case we're just touching up the audio.
