The MP3 file's metadata (like ID3 tags containing album art or comments) is likely causing a false positive error. Try re-encoding the MP3 file without metadata using Audacity or a dedicated tag editor.

With the fixes and tools outlined here—from a simple container extraction with FFmpeg to the robust reliability of MKVToolNix—you now have everything you need to troubleshoot this error and get back to editing your videos, with the perfect soundtrack in place.

The happens because you are trying to import an audio track wrapped inside a container (like M4A, MP4, or MKV) or using an unsupported, compressed format like OGG/Vorbis and raw FLAC. Avidemux does not invoke demuxers for external audio tracks . It strictly requires raw, un-muxed audio streams or uncompressed PCM formats like WAV.