RMVB to AU Converter

RMVB to AU Converter

RMVB (RealMedia Variable Bitrate) is a 2000s-era RealNetworks video container that wraps a RealVideo picture stream and a low-bitrate RealAudio soundtrack. AU is one of the oldest digital audio formats — a bare Sun Microsystems container from the Unix workstation era. This converter pulls the audio out of an RMVB file, decodes the RealAudio track, and writes it back out as a standard AU file for Unix, Java, or telephony pipelines that still expect that format.

RMVB Format at a Glance

AU Format at a Glance

Why Extract RMVB Audio to AU?

This is a niche, compatibility-driven conversion rather than a quality upgrade. If you are feeding audio into an older Unix toolchain, a Java program that loads clips through AudioClip, or a telephony/voicemail system that speaks μ-law, AU is the container those tools were built around. Pulling the soundtrack out of an RMVB video into a plain AU file drops the RealMedia wrapper entirely and gives you a header-plus-data file that almost any Unix audio library can read.

Be realistic about quality. RMVB audio is usually the RealAudio Cook codec encoded at a low bitrate for small file sizes, so the source is already lossy. Converting to AU re-encodes that decoded stream — by default into 8-bit μ-law telephony companding — and will not add back detail the RealAudio track never stored. You are changing the wrapper and encoding, not restoring fidelity. For everyday listening, extracting to MP3 is smaller and plays everywhere; choose AU only when a specific Unix or Java pipeline requires it.

How to Convert RMVB to AU

1. Upload Your RMVB File: Drag and drop your .rmvb file onto the page or click "Add Files". You can queue several clips and convert them with the same settings.
2. Set the AU Output Options: Under Advanced Options, leave Audio Sample Rate and Audio Channel on "Original" to match the source, or downmix to mono and lower the sample rate for a smaller telephony-style file.
3. Trim to the Part You Need (Optional): Use the Trim control to set a start point and duration so the AU file contains only the segment you want, instead of the whole soundtrack.
4. Convert and Download: Click Convert and save your AU file. Files upload over an encrypted connection, are processed on our servers, and are deleted automatically after a few hours. No sign-up, no watermark.

Frequently Asked Questions

Does converting RMVB to AU improve the audio quality?

No. RMVB carries a lossy RealAudio track, so the detail lost during its original low-bitrate encoding is already gone. Re-encoding that audio to AU cannot recover anything — and the default 8-bit μ-law output can trim a little more, being telephony-grade companding — so you get a larger file that sounds no better. (Selecting 16-bit PCM in the advanced options preserves the decoded audio in full, but still can't exceed the source quality.)

What encoding does the AU output use — μ-law or PCM?

The converter writes 8-bit μ-law (G.711) by default — the same encoding classic SunOS-era AU files used, though at the source's sample rate unless you lower it to 8000 Hz. If you want uncompressed linear PCM instead, select 16-bit big-endian PCM (PCM_S16BE) in the advanced options; A-law is also available.

Will the AU file be larger than the original RMVB audio track?

Almost always. AU stores decoded audio as raw samples, while RMVB's RealAudio is heavily compressed. The default 8-bit μ-law output runs about 5.3 MB per stereo minute at 44.1 kHz (one byte per sample per channel), so a 3-minute clip lands around 16 MB — and selecting 16-bit PCM doubles that to roughly 32 MB. Either way the AU file dwarfs the low-bitrate source it came from.

What programs can open an AU file?

VLC, Audacity, and most cross-platform audio libraries read AU, as do Java programs and traditional Unix sound utilities like play (SoX). Some general media players do not recognise it, since AU never became a consumer format — if a player refuses it, convert the audio to a mainstream format instead.

Why would I choose AU over WAV or MP3 for RMVB audio?

Only for compatibility with a system that specifically expects AU — a legacy Unix workflow, a Java applet or app that loads clips as AU, or a telephony stack built on μ-law. For portability and small size, MP3 is a better choice, and WAV is the more common uncompressed option on Windows and macOS.

Can AU preserve the metadata, chapters, or video from the RMVB file?

No. AU has a minimal 24-byte header with room only for the encoding, sample rate and channel count — there are no fields for tags, cover art or chapters, and it is audio-only, so the RealVideo picture stream is discarded. If you need to keep the video, convert to a video format such as MP4 instead.

Why is the AU file so much larger than the RMVB?

Because AU here stores one raw byte per sample per channel (the 8-bit μ-law default) while RMVB's RealAudio track was heavily compressed. RMVB was built for low-bitrate streaming, so its audio might run a few kilobits per second; the same audio written as μ-law AU at 44.1 kHz stereo balloons to roughly 5.3 MB per minute — about 10 MB if you select 16-bit PCM. The extra size buys no quality — it can't add detail the compressed source never had — so if size matters, RMVB to MP3 keeps it small instead.

Is my RMVB file kept private during the conversion?

Yes. Your file is uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours. There is no sign-up, no watermark, and files are never shared or made public. On big RMVB files, the main wait is upload time rather than the conversion itself.