Files using highly unusual sampling rates (outside the standard 44.1 kHz or 48 kHz) or specific compressed formats can cause Avidemux's internal demuxer to fail upon import. How to Fix the Error (Step-by-Step Solutions)
Avidemux cannot use audio that is already muxed into a container like .m4a or .mp4 as an external track. It expects the raw stream (e.g., ADTS-encapsulated AAC). avidemux+cannot+use+that+file+as+audio+track
The audio file is in a container or codec that Avidemux cannot parse (e.g., specialized FLAC, Vorbis, or proprietary formats). Files using highly unusual sampling rates (outside the
If none of the above works, your issue is likely with the video track itself, not the audio. not the audio.