Converting your file to an uncompressed, standard WAV format bypasses all demuxing restrictions in Avidemux. Cannot use mp3 as audio track - Avidemux.org
This is, by far, the most frequent offender. You try to add a file like song.m4a or audio.mp4 , and Avidemux rejects it.
To resolve this, you must convert your audio file into a raw or simple format that Avidemux recognizes. Convert to WAV avidemux cannot use that file as audio track
If you just need to merge an audio file with a video without re-encoding, MKVToolNix is often more robust for "multiplexing" external tracks into MKV files without these strict format restrictions. Correct Workflow in Avidemux Once you have a compatible raw file (like a .wav ): How to add audio to a muted/silent video with avidemux
Avidemux is a beloved, free, and open-source video editor, primarily used for simple cutting, filtering, and encoding tasks. Its lightweight nature and non-linear workflow make it a go-to tool for quick edits. However, users frequently encounter a frustrating roadblock: the dreaded red error message at the bottom of the interface: Converting your file to an uncompressed, standard WAV
Instead of adding an external track, use (GUI or command line) to merge your video + the external audio into a single MKV. Then open that MKV in Avidemux. Avidemux handles MKV’s internal audio tracks much better than external references.
file that is actually an MP4 container without video. Avidemux cannot invoke demuxers for external tracks in these formats. Metadata Interference To resolve this, you must convert your audio
If none of the above solutions work, try using a different audio file to see if the issue is specific to the file.