Free online AUD to FLAC converter

FLAC is useful when an older game or archive provides audio as AUD but a modern player, editor, or music library requires a standard lossless format. Converting preserves the decoded audio while making it easier to play, tag, edit, and archive.

What the AUD format is

In the Audio category, AUD usually means the Westwood Studios audio format used by games such as Command & Conquer, Red Alert, and Dune II. These files commonly contain mono game music, speech, or sound effects encoded as uncompressed audio or Westwood/IMA-style ADPCM.

AUD files are normally extracted from game data or created by Westwood-compatible game and archive tools rather than by modern recording applications. The .aud extension is not a universal audio standard, so files from unrelated software may require a different decoder.

What the FLAC format is

FLAC is a lossless audio codec. It reduces file size without discarding decoded samples, supports metadata such as title and artist, and is widely supported by desktop players, media servers, archival tools, and audio editors.

Use FLAC when you need lossless storage or compatibility with current audio software. FLAC may not be smaller than an already heavily compressed AUD file, and conversion cannot restore quality that was discarded by the original AUD encoding.

How to convert AUD to FLAC

Using FFmpeg

Install an FFmpeg build with the Westwood AUD demuxer and ADPCM decoder, then check that the file is recognized:

ffprobe input.aud

Convert it directly to FLAC with:

ffmpeg -i input.aud -c:a flac output.flac

FFmpeg reads the sample rate and channel layout from the AUD header. Do not add resampling or channel-conversion options unless the destination specifically requires them.

To convert several files in a shell, use a separate output name for each source:

for f in *.aud; do ffmpeg -i "$f" -c:a flac "${f%.aud}.flac"; done

If FFmpeg does not recognize the file

Some AUD variants are better handled by vgmstream, a tool for game audio. Decode the file to WAV:

vgmstream-cli -o decoded.wav input.aud

Then encode the decoded WAV as FLAC:

ffmpeg -i decoded.wav -c:a flac output.flac

On 101convert.com, you can also convert the file online for free without installing software.

Quality and compatibility considerations

The conversion to FLAC is lossless only from the decoder's output: it does not undo lossy ADPCM compression already present in the AUD file. Keep the original AUD alongside the FLAC if the source is archival or may need to be reprocessed.

Compare the FLAC duration, sample rate, channel count, and audible start/end points with the source. Some game AUD files contain short effects or unusual headers that generic applications may interpret incorrectly; a game-audio decoder is preferable when FFmpeg reports incorrect duration or metadata.