Avidemux’s "Copy" mode hates Variable Bitrate (VBR) MP3 files. When you cut video on keyframes, VBR audio loses sync because the bitrate fluctuates. Avidemux is old-school; it prefers Constant Bitrate (CBR).

The Fix: Convert your VBR MP3 to CBR MP3 or PCM WAV using a tool like Audacity or FFmpeg before loading it into Avidemux.

FFmpeg one-liner: ffmpeg -i input_vbr.mp3 -b:a 192k -acodec libmp3lame output_cbr.mp3

If none of the above works, your issue is likely with the video track itself, not the audio.

“Cannot use that file as audio track” = Avidemux’s polite way of saying “I don’t like this file’s format, sample rate, or codec.”
The universal fix: Convert to 48 kHz WAV (PCM 16‑bit) and retry. If still fails, use FFmpeg to mux externally.

The error message " cannot use that file as audio track " in Avidemux typically occurs when the software's demuxer cannot properly parse the external audio file you are trying to add. This often stems from container incompatibility, metadata issues, or outdated software versions. avidemux.org Common Causes & Solutions Container Incompatibility (M4A/MP4/MKV)

: Avidemux cannot use audio that is already inside a container (like : You must provide the "raw" audio stream (e.g., ) or convert the file to a standard before importing. Metadata Interference

: Files from certain sources (like Traktor) may have metadata headers that confuse Avidemux, leading it to misread the file's sample rate or format.

: Use a tool to strip metadata or "clean" the audio file by re-saving it in a basic audio editor. Unsupported Bit Depth or Codecs

: Avidemux may reject specific high-fidelity formats, such as 24-bit WAV : Convert the audio to 16-bit WAV at 44.1kHz or 48kHz for the best compatibility. Outdated Software Version

: Older versions of Avidemux (e.g., 2.7.x) had known bugs related to external audio track recognition. : Upgrade to the latest stable release (e.g.,

or newer) or try a nightly build, which often includes fixes for these parsing errors. avidemux.org How to Correctly Add an External Track Cannot use mp3 as audio track - avidemux.org

Here’s a post you can use on forums like Reddit, VideoHelp, or Super User:

Title: Avidemux error: "Cannot use that file as audio track" – how to fix?

Post:

Hi everyone,

I’m trying to replace or add an external audio track in Avidemux, but when I go to Audio → Select Track and choose my file (MP3 or M4A), I get the error:

Cannot use that file as audio track

Both the video file and the audio file play fine in other players. I’ve tried:

Has anyone found a reliable workaround? Is there a specific format Avidemux expects?

Thanks!

If you want a shorter version for social media (e.g., Twitter/Mastodon):

Getting "cannot use that file as audio track" in Avidemux when adding external audio. File plays fine elsewhere. Tried WAV, MP3 CBR, matching sample rate. Any fix? #Avidemux

Make sure you're using the latest version of Avidemux. Visit the official website to download the latest version, which may include bug fixes or support for additional audio formats.

ffmpeg -i your_audio.mp3 -ar 48000 -ac 2 -c:a pcm_s16le output.wav

Or to CBR MP3:

ffmpeg -i your_audio.opus -ar 48000 -b:a 192k output_cbr.mp3

Instead of the current hard error modal dialog, the new behavior would be:

If the file is already MP3 but VBR, try:

ffmpeg -i input.mp3 -c:a copy -ar 48000 output.mp3

But this only works if the container supports re‑declaring the rate; often you must re‑encode.