Free online RM to AU converter

Source format: RM

RM is a RealMedia multimedia container format associated with RealNetworks. It was widely used for streaming audio and video over the internet, especially in the late 1990s and early 2000s. RM files often contain compressed media encoded with RealAudio or RealVideo codecs and were common for online clips, archived broadcasts, and legacy media libraries.

Because RM is an older proprietary format, support in modern players is limited. It is still encountered in archived content, old training materials, and legacy web media collections.

Target format: AU

AU is a simple audio file format originally developed for Unix systems. It is commonly used for basic audio storage and exchange, especially in older software environments and technical workflows. AU files may contain uncompressed PCM audio or compressed audio depending on the variant, and they are valued for their simplicity and broad support in Unix-like tools.

The main advantages of AU are its straightforward structure and compatibility with many audio utilities. It is most often used for legacy audio, system sounds, and interoperability with older Unix-based applications.

How to perform the conversion

The best approach is to use a desktop media tool that can read RM and export audio to AU. FFmpeg is usually the most practical choice if your RM file contains an audio stream that can be decoded.

1. Install FFmpeg on your computer.
2. Open a terminal or command prompt.
3. Run a command such as ffmpeg -i input.rm output.au.
4. If the RM file contains both audio and video, FFmpeg will extract and convert the audio stream into the AU container when the output filename ends in .au.
5. Check the resulting file in an audio player that supports AU.

If the RM file contains multiple streams or you want to control the audio codec, you can specify options explicitly. For example, to create uncompressed AU audio, use a PCM-compatible output if supported by your build of FFmpeg. In many cases, the default stream selection is sufficient for simple conversions.

Another option is VLC media player, which can sometimes open RM files and convert them through Media → Convert / Save. However, FFmpeg is generally more reliable for legacy RM sources and batch conversion.

Notes on quality, compatibility, or limitations

RM is a legacy format, so conversion success depends on whether your FFmpeg build includes the needed demuxer and decoder support. Some RM files use older RealAudio/RealVideo variants that may not decode perfectly in modern software.

Because AU is primarily an audio format, any video content in the RM file will be discarded during conversion. If the RM file contains only audio, the conversion is straightforward. If it contains video plus audio, only the audio track should be preserved in the AU output.

Quality cannot improve during conversion: if the RM source is already heavily compressed, the AU output will reflect the decoded audio quality of the original. For best results, use the highest-quality source file available and avoid repeated re-encoding.

Compatibility is generally good for AU in Unix-like environments, but some modern consumer players may have limited support. If you need wider playback compatibility, a more common audio format such as WAV or MP3 may be preferable.