Convert WEBA to AU — Free Online Tool
Convert WEBA audio files (WebM containers with Opus or Vorbis encoding) to Sun AU format using PCM signed 16-bit big-endian encoding. This tool decodes your compressed web audio and re-encodes it as uncompressed PCM, producing a lossless-quality AU file compatible with Unix systems and legacy audio toolchains.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your WEBA file here
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Free — no uploads, no signups. Your files never leave your browser.
Settings
Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
WEBA files store audio using lossy compression codecs — typically Opus or Vorbis — inside a WebM container optimized for web streaming. AU files, developed by Sun Microsystems, use a minimal fixed header and store raw PCM audio data with no further compression. During this conversion, FFmpeg fully decodes the compressed Opus or Vorbis audio stream from the WEBA container, then re-encodes it as PCM signed 16-bit big-endian audio (pcm_s16be) and writes it into the AU container. Because the source is lossy-compressed, the output is PCM-accurate to the decoded signal — meaning no further quality is lost in this step, but the quality ceiling is already set by the original WEBA encoding. The -vn flag is applied to explicitly suppress any video stream handling, though WEBA is audio-only. File sizes will increase significantly compared to the source WEBA file because PCM is uncompressed.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary. In the browser tool, this runs via FFmpeg.wasm compiled to WebAssembly — no server or local installation is required. |
-i input.weba
|
Specifies the input file — a WEBA audio file containing a WebM container with Opus or Vorbis compressed audio. FFmpeg automatically detects the WebM container and selects the appropriate decoder (libopus or libvorbis) based on the stream's codec. |
-c:a pcm_s16be
|
Sets the audio codec for the output to PCM signed 16-bit big-endian, which is the standard uncompressed audio encoding for the AU format. This decodes the lossy Opus or Vorbis stream and writes every audio sample as a raw 16-bit integer in big-endian byte order. |
output.au
|
Specifies the output filename with the .au extension. FFmpeg uses this extension to select the Sun AU muxer, which writes the minimal AU header followed by the raw pcm_s16be audio data — producing a file immediately readable by Unix audio tools and Java's javax.sound API. |
Common Use Cases
- Preparing web-sourced audio for processing in legacy Unix audio tools or signal processing pipelines that expect raw PCM in AU format
- Supplying audio to older Sun workstation software, NeXTSTEP applications, or retro computing environments that natively read .au files
- Converting downloaded WEBA podcast or voice recordings into a headerless-style PCM format for acoustic analysis tools that consume AU
- Archiving Opus-encoded web audio in an uncompressed PCM format to avoid further lossy transcoding steps in a post-production chain
- Feeding WEBA-sourced audio into Java applications, which historically use AU as a default supported audio format via the javax.sound API
- Stripping the WebM container and Opus compression from browser-recorded audio (e.g., MediaRecorder API output) to produce a simple PCM file for hardware audio devices or embedded systems
Frequently Asked Questions
No. The WEBA format uses lossy compression (Opus or Vorbis), which permanently discards audio data during the original encoding. Converting to AU simply decodes the compressed audio to raw PCM — it accurately represents what the WEBA file sounds like, but cannot recover the detail that was lost when the WEBA was first created. The output AU file will have no further quality degradation beyond what was already present in the source.
WEBA files use Opus or Vorbis compression, which can reduce audio data size by 10x or more compared to uncompressed PCM. AU files with pcm_s16be encoding store every audio sample as a raw 16-bit integer with no compression, so a 3-minute WEBA file at 128k bitrate (roughly 2.9 MB) will expand to approximately 30–35 MB as an AU file at standard 44.1kHz stereo. This is expected behavior and is the trade-off of working with PCM-based formats.
AU with pcm_s16be supports a wide range of sample rates (8kHz, 16kHz, 22.05kHz, 44.1kHz, 48kHz) and stereo or mono audio, so most WEBA files will convert without resampling. However, Opus audio in WEBA files is often encoded at 48kHz, which carries over cleanly to AU. If your source is mono voice audio at 16kHz or 8kHz (common in WebRTC recordings), that sample rate is preserved in the output AU file.
No. The AU format has an extremely minimal header — it stores only the essential audio encoding parameters (sample rate, channels, encoding type, and an optional annotation field). It does not support ID3 tags, Vorbis comment metadata, or any of the title, artist, or album fields that may be present in the WEBA container. All such metadata is discarded during this conversion.
Yes. The AU format supports several PCM variants. You can replace pcm_s16be with pcm_s8 (8-bit signed, lower quality), pcm_u8 (8-bit unsigned), pcm_alaw (G.711 A-law, commonly used in telephony), or pcm_mulaw (G.711 μ-law, also used in telephony). For example: ffmpeg -i input.weba -c:a pcm_mulaw output.au produces a telephony-standard μ-law AU file. The default pcm_s16be is recommended for general use as it provides the best fidelity within the AU format.
On Linux or macOS, you can use a shell loop: for f in *.weba; do ffmpeg -i "$f" -c:a pcm_s16be "${f%.weba}.au"; done. On Windows Command Prompt, use: for %f in (*.weba) do ffmpeg -i "%f" -c:a pcm_s16be "%~nf.au". This applies the same pcm_s16be conversion to every WEBA file in the current directory and outputs a corresponding .au file for each. The browser-based tool on this page processes one file at a time.
Technical Notes
The AU format's pcm_s16be codec stores samples as big-endian 16-bit signed integers, which is native to SPARC and MIPS architectures but requires byte-swapping on x86/x64 systems — most modern software handles this transparently. Because WEBA's Opus codec operates internally at 48kHz, the decoded PCM handed to the AU muxer is typically 48kHz, which AU supports natively, avoiding any resampling artifacts. If the source WEBA contains Vorbis instead of Opus, the decoding path differs internally but the output PCM format is identical. One known limitation of the AU container is its lack of a chunk-based structure — the audio data follows a fixed 24-byte header with no support for metadata, chapters, or multiple streams. The -vn flag in the command is a safety measure to prevent FFmpeg from failing or producing unexpected output if the input container unexpectedly carries a video stream, though standard WEBA files are audio-only. For maximum compatibility with legacy Unix software, ensure the output sample rate matches what the receiving application expects, as AU files do not auto-resample on playback.