Free online AC3 to AU converter

AC3 is an audio compression format commonly used for surround sound in movies, DVDs, and broadcasts. AU is a simple audio container format originally used on Unix systems, often storing uncompressed or lightly compressed audio. Converting AC3 to AU usually means decoding the AC3 audio and saving it into an AU file, often with a compatible PCM codec.

Why convert ac3 to au

You may need this conversion when working with older Unix-based tools, legacy audio workflows, or systems that accept AU more readily than AC3. Since AU is widely recognized by many audio utilities, it can be useful for compatibility and basic editing.

Best software for ac3 to au conversion

FFmpeg is the best overall choice for this conversion because it is free, fast, reliable, and supports both formats. It can decode AC3 and write AU files with a suitable audio codec. For a graphical option, Audacity can also import AC3 through supported libraries and export to AU if your setup supports the format.

How to convert with ffmpeg

Use FFmpeg from the command line for the most direct conversion. A typical command is:

ffmpeg -i input.ac3 output.au

If you need to ensure a standard PCM output, you can specify the audio codec explicitly:

ffmpeg -i input.ac3 -acodec pcm_s16be output.au

This creates an AU file with 16-bit big-endian PCM audio, which is commonly compatible with AU readers.

How to convert with audacity

In Audacity, open the AC3 file if your installation supports it, then export the audio as AU. The general workflow is:

File → Open

File → Export → Export Audio

Choose AU as the output format and select the desired encoding if available.

Important conversion notes

AC3 is often multichannel, while AU may be used more commonly for simpler audio setups. During conversion, some channel layouts or metadata may not carry over exactly. If preserving surround sound is important, verify that the target AU workflow supports the channel count and codec you need.

Also note that AU is an older format, so file size and compatibility depend heavily on the chosen audio encoding. For best results, use FFmpeg and confirm the output with a media player or audio utility after conversion.

Recommended choice

Best converter: FFmpeg

Best for beginners with a GUI: Audacity

If you want the most dependable and flexible conversion, FFmpeg is the top recommendation for AC3 to AU.