Xvid to AU

How to Convert Xvid to AU Online

1. Upload Your Xvid File: Drag and drop your Xvid-encoded AVI into the drop zone or click "+ Add Files" to browse. Batch uploads work — queue several clips and the converter processes each one with the same settings.
2. Pick File Compression: Choose a Quality Preset (Highest, Very High, High, Medium, Low, Very Low, Lowest) for variable bitrate output, or switch to Constant Bitrate and lock in 64, 128, 192, or 256 kbps. For mu-law telephony output, 64 kbps CBR matches the classic 8-bit / 8 kHz envelope. Prefer linear PCM AU? Pick a high preset and let the encoder run uncompressed at your chosen sample rate.
3. Set Audio Channel and Audio Sample Rate (Optional): Audio Channel offers Original, Mono, or Stereo — pick Mono for telephony, IVR prompts, or Java 1.1-compatible playback. Audio Sample Rate ranges from 8000 Hz (G.711 telephony) through 11025, 22050, 44100, up to 48000 Hz for music-quality output.
4. Trim and Convert: Open Trim to set a start time and duration in HH:MM:SS.mmm format if you only need a clip — the rest of the video is discarded before encoding. Click Convert and download. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared.

Why Convert Xvid to AU?

Xvid is an open-source MPEG-4 Part 2 (Advanced Simple Profile) video codec, first released in 2001 and almost always wrapped in an AVI container alongside an MP3, AC-3, or AAC audio track. AU is a much older container: Sun Microsystems introduced it for Unix workstations, NeXT adopted it, and it became the default audio format for early Web pages and Java applets. The reason to extract Xvid audio specifically to AU is interoperability with software that still expects the .snd magic-number header rather than RIFF (WAV) or MP4.

• Java Sound API compatibility — Java 1.1's audio playback only supported 8-bit μ-law mono AU at 8 kHz. Modern javax.sound.sampled reads many formats, but .au remains the safest bet for legacy applets, JNLP demos, and university coursework that still ships from Sun's old reference packages.
• Telephony and IVR systems — Asterisk, FreePBX, and many SIP platforms accept μ-law AU prompts at 8 kHz mono out of the box. Extract a narration track from an Xvid training video and drop it straight into the dial-plan recordings folder.
• Unix and Solaris archives — audiotool, audioplay, and SunOS desktop sound services natively read AU. If you're maintaining a museum-grade Solaris box or a NetBSD audio pipeline, AU avoids the pkgsrc gymnastics of installing a modern decoder.
• Bioacoustics and lab software — older versions of Praat, MATLAB Signal Processing Toolbox, and Octave's auread/auwrite work with AU more reliably than newer formats. Researchers digitising Xvid lecture recordings often archive the audio as AU for long-term reproducibility.
• Embedded and retro hardware — SPARC workstations, BeOS, and some vintage embedded SoCs ship with AU decoders in ROM. WAV or MP3 may need extra decoding muscle that the device doesn't have.

Xvid (AVI) vs AU — Format Comparison

Sample Rate and Encoding Quick Guide

Frequently Asked Questions

Why is the AU file so much larger than the original Xvid audio track?

If your source AVI carries MP3 or AC-3 audio and you transcode to linear-PCM AU, the AU is uncompressed and will land roughly 8-10x bigger for the same duration. To shrink it, pick a Constant Bitrate preset (64-128 kbps) so the encoder uses a compressed AU profile, or drop the sample rate to 22050 Hz mono if the content is voice. Telephony-grade 8 kHz μ-law AU is actually smaller than 128 kbps MP3.

Should I pick mu-law (8 kHz) or 44.1 kHz linear PCM AU?

Pick μ-law at 8 kHz only if the consumer is telephony, an IVR, or a Java 1.1 applet — those systems literally cannot play anything else, and the format is locked to that envelope by G.711. For everything else (Unix workstations, modern Java, audio archives, Praat/MATLAB), 44.1 kHz linear PCM is a better default: it preserves voice clarity and music transients, and every AU decoder written since the late 1990s reads it.

Does Xvid always come inside an AVI?

Almost always, yes. Xvid is an MPEG-4 ASP video codec, not a container — the bitstream needs a wrapper. AVI was the dominant choice during Xvid's heyday (2003-2010) for compatibility with DivX hardware players. You'll occasionally see Xvid in MKV or MP4, but if your file ends in .xvid or .avi, this converter accepts it and pulls the audio track out for transcoding.

Can I trim before converting to save processing time?

Yes — open the Trim section, enter a start time and duration (HH:MM:SS.mmm). Only the trimmed range is decoded and re-encoded, which is significantly faster than converting the full clip and editing afterwards. This is especially handy when you only need a 10-second voice line from a 45-minute Xvid lecture.

Will modern browsers play the resulting AU file?

Native browser support for AU has effectively disappeared. Safari historically played AU via QuickTime, but no current browser ships an AU decoder by default. If you need browser playback, convert to WAV or MP3 instead — see Xvid to MP3 or Xvid to WAV. AU is the right choice when the consumer is server-side software, a desktop audio tool, or a legacy Java/Unix environment.

Why does my AU file sound muffled at 8000 Hz?

8 kHz sampling has a Nyquist limit of 4 kHz, so anything above that — sibilants, music harmonics, room ambience — gets filtered out. That's by design for telephony (G.711 was tuned for the 300-3400 Hz voice band). If the muffling is unacceptable, raise the Audio Sample Rate to at least 22050 Hz; the file gets larger but the high frequencies return.

Does the converter support a-law as well as mu-law AU output?

The AU container supports μ-law, A-law, linear PCM, and ADPCM encodings per Sun's spec. The default for compressed AU output here is μ-law (the North American / Japanese telephony standard). If your downstream system requires A-law (the European E1 standard), check the encoding the receiver expects — for purely European telephony pipelines, you may need to post-process with ffmpeg -acodec pcm_alaw to switch the codec field after this conversion.

Can I convert several Xvid videos to AU at once?

Yes. Add multiple files via the "+ Add Files" button or drag-and-drop a batch. Each file converts with the same Audio Channel, Sample Rate, and File Compression settings you pick — useful for converting a folder of training videos into a uniform set of IVR prompts. Each file processes independently in your browser, so a slow one won't block the rest.

What's the difference between AU and AIFF?

Both are old uncompressed-audio containers, but AIFF (Apple/SGI, 1988) uses big-endian linear PCM and was tied to early Macs and IRIX, while AU (Sun, late 1980s) supports μ-law / A-law / PCM and dominated Unix workstations and early Java. If your target platform is macOS or audio-production software, prefer AIFF; if it's Solaris, NetBSD, IVR, or Java legacy, prefer AU.