I tried adding a FLAC audio file to a H.264 video on Avidemux, but I keep running into an error saying I can't add it. What should I do to fix it?
FLAC raw or ogg-encapsulated streams are not supported for external audio tracks in Avidemux. You need to convert them into uncompressed 16 or 24 bit signed integer WAV files first (which is lossless) using flac executable or a tool which provides the functionality like approximately built ffmpeg.