Free online M4B to AU converter

M4B is an audiobook-oriented audio format based on AAC, often used by Apple devices and audiobook apps because it can store chapter markers and metadata. AU is an older Sun/NeXT audio format that is simple, widely recognized, and commonly used for basic uncompressed or lightly compressed audio data.

What is m4b to au conversion?

M4B to AU conversion means changing an audiobook file in the M4B container into an AU audio file. This is usually done for compatibility with older systems, audio tools, or workflows that require the AU format. During conversion, chapter information and some M4B-specific metadata are usually lost because AU does not support those audiobook features.

When to convert m4b to au

• For compatibility with legacy Unix, Sun, or older audio software.
• For simple audio processing in tools that accept AU more readily than M4B.
• For archival or technical workflows where AU is required as an intermediate format.

Best software for m4b to au conversion

FFmpeg is the best overall converter for this task because it is free, fast, reliable, and supports both formats. It can preserve audio quality as needed and gives precise control over output settings. For users who prefer a graphical interface, VLC media player or Audacity can also help, though FFmpeg is usually the most dependable choice.

How to convert m4b to au with ffmpeg

Use a command like this:

ffmpeg -i input.m4b output.au

If you need to choose a specific audio codec for AU output, you can adjust the command depending on the desired compatibility and quality. In many cases, FFmpeg will automatically select a suitable format for AU.

How to convert m4b to au in a gui app

In a graphical converter, the general steps are:

1. Open the M4B file.
2. Choose AU as the output format.
3. Set audio quality or codec options if available.
4. Start the conversion and save the result.

In some applications, the menu path may look like File → Open and then File → Export or Convert.

Important things to know

• Chapter markers from M4B are usually not preserved in AU.
• Metadata such as audiobook title, author, and cover art may be removed.
• Audio quality depends on the chosen codec and settings during conversion.
• File size may increase if AU is saved as uncompressed audio.

Recommended choice

If you want the most reliable and flexible solution, choose FFmpeg. If you need a simple interface, use a converter that supports M4B input and AU output, but verify that it handles audiobook files correctly.