If none of the above works, your issue is likely with the video track itself, not the audio.
(fastest fix) Use ffmpeg (or Audacity) to convert the audio to WAV (16-bit PCM) or AC3 . FFmpeg command: ffmpeg -i input_audio.m4a -c:a pcm_s16le output_audio.wav Then load the WAV file in Avidemux → Audio → Select Track → External Track. avidemux+cannot+use+that+file+as+audio+track
External AAC tracks often need to be in an ADTS or LATM envelope; standard MPEG-4 encapsulated AAC is frequently rejected. How to Fix the Error 1. Convert the Audio to a Compatible Format If none of the above works, your issue
Sometimes Avidemux prefers it if you don't use the "Select Track" menu immediately. If none of the above works
