MP4 to AU Converter

Extract audio from MP4 and save as Sun AU format online

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Unix Standard Audio

AU is the native audio format for Sun and Unix systems. Converting MP4 audio to AU gives you files ready for Unix-based workflows.

Encoding Options

Choose between mu-law, A-law, or PCM encoding. Match the AU output to your system requirements and quality standards.

Secure Conversion

Uploaded MP4 files are removed immediately. AU results are deleted from our servers within 24 hours.

How to convert MP4 to AU

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

Choose au or any other format you need as a result (more than 200 formats supported)

Let the file convert and you can download your au file right afterwards

About formats

MP4 (MPEG-4 Part 14) is the most widely used multimedia container format in the world, standardized by the Moving Picture Experts Group as part of the MPEG-4 specification in 2003. Built on the ISO base media file format (MPEG-4 Part 12), which itself drew from the Apple QuickTime container, MP4 uses a hierarchical atom/box structure that can encapsulate virtually any type of media data. The container most commonly packages H.264 or H.265 video with AAC audio, though it also supports a wide range of alternative codecs including AV1, VP9, MPEG-4 Visual, AC-3, and ALAC. The design supports advanced features such as streaming hints for progressive download and adaptive streaming, chapter markers, multiple audio and subtitle tracks, metadata tags, and embedded thumbnail images. A standardized structure and broad codec support have made MP4 the default choice for online video platforms, mobile devices, digital cameras, and operating system media libraries. HTML5 video with H.264 in MP4 is supported by every major web browser, establishing the combination as the universal baseline for web video delivery. Efficient packaging overhead, combined with the compression capabilities of modern codecs it carries, enables high-quality video distribution at practical file sizes across bandwidth-constrained networks and storage-limited devices.

Developer: Moving Picture Experts Group

Initial release: 2003

AU is an audio file format introduced by Sun Microsystems for its Unix workstations and the NeXT platform. It features a minimal 24-byte header specifying data offset, size, encoding type, sample rate, and channel count, followed by the audio payload. AU supports numerous encodings, including uncompressed linear PCM at various bit depths, mu-law and A-law companding (logarithmic compression used in telephone systems), and several ADPCM variants. This versatility made AU a workhorse across early Unix environments, web audio (Java applets defaulted to AU), and telephony applications. One advantage is simplicity: the compact header and straightforward structure make it trivial to parse, generate, and stream programmatically. The built-in mu-law option provides another benefit, delivering reasonable voice quality at just 8 KB per second — half the rate of 16-bit uncompressed audio — invaluable when storage and bandwidth were scarce. Although modern formats have largely supplanted AU in consumer applications, it retains a foothold in scientific computing and audio processing pipelines where minimal overhead and reliable cross-platform behavior are valued.

Developer: Sun Microsystems

Initial release: 1992

Frequently Asked Questions

Why convert MP4 to AU?

AU is the standard audio format for Sun/Unix systems and Java audio APIs. Converting is useful for Unix development and Java-based applications.

What opens AU files?

VLC, Audacity, and SoX play AU files on any platform. Unix systems handle AU natively, and Java's sound API uses it as a default format.

Is AU still relevant?

AU remains important in Unix environments and Java development. It is a simple, well-documented format with broad cross-platform tool support.

Can I batch convert?

Upload multiple MP4 files and extract each audio track to a separate AU file in one session. All files process in parallel.

What encoding does AU use?

AU supports mu-law, A-law, and linear PCM encoding. The choice depends on your target platform and quality requirements.

Does AU support stereo?

Yes — AU handles both mono and stereo audio. Multi-channel configurations are also possible depending on the encoding used.

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MP3 to AU

WAV to AU

MP4 to AU

M4A to AU

OGG to AU

AAC to AU

MPEG to AU

FLAC to AU

WMA to AU

3GP to AU

OPUS to AU

AMR to AU

ASF to AU

AVI to AU

WEBM to AU

MOV to AU

WVE to AU

AIFF to AU

FLV to AU

MKV to AU

SND to AU

CAF to AU

WMV to AU

MP2 to AU

MPG to AU

AC3 to AU

M4R to AU

3G2 to AU

AAF to AU

AV1 to AU

MP4 to AU Quality Rating

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