Let’s diagnose the problem by looking at your current Avidemux settings.
Sometimes, Avidemux simply cannot handle a specific file. It is not a professional audio engineer. If you have spent 20 minutes troubleshooting, consider these alternatives for muxing external audio: avidemux+cannot+use+that+file+as+audio+track
If MKVToolNix rejects your audio file, your file is truly corrupted. If MKVToolNix accepts it but Avidemux doesn’t, then Avidemux is the bottleneck. Let’s diagnose the problem by looking at your
Instead of using Audio > Select Track, try a different workflow to merge audio: If MKVToolNix rejects your audio file, your file
This tricks Avidemux into treating the audio as the primary stream, which bypasses some validation checks.