Convert WTV to AU — Free Online Tool
Convert WTV (Windows Media Center recorded TV files) to AU (Sun AU PCM audio) entirely in your browser, extracting the audio stream and encoding it as 16-bit big-endian PCM — the native codec for the AU format used on Unix systems. This is ideal for stripping broadcast TV recordings down to raw, uncompressed audio for Unix-based workflows or legacy audio tools.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your WTV file here
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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
WTV files are DVR containers produced by Windows Vista/7/8 Media Center, typically holding H.264 or MJPEG video alongside AAC or MP3 audio. When converting to AU, the video stream is completely discarded — AU is a purely audio format with no video container support. The audio stream is re-encoded (transcoded) from AAC or MP3 into 16-bit signed big-endian PCM (pcm_s16be), which is the standard codec for Sun AU files. This transcoding step introduces no additional lossy compression since PCM is uncompressed, but it does decompress whatever lossy audio was in the original WTV first. The resulting AU file will have a simple binary header followed by raw PCM audio samples, making it immediately readable by Unix audio utilities, scientific audio tools, and legacy software that predates modern formats like WAV or FLAC.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program, the open-source multimedia processing engine that performs the WTV-to-AU conversion entirely within your browser via WebAssembly (FFmpeg.wasm). |
-i input.wtv
|
Specifies the input file — a WTV container produced by Windows Media Center, which may contain H.264 or MJPEG video, AAC or MP3 audio, and embedded DVR metadata. FFmpeg reads and demuxes all streams from this file. |
-c:a pcm_s16be
|
Instructs FFmpeg to encode the output audio as 16-bit signed big-endian PCM, which is the standard and most common audio encoding for Sun AU files. This transcodes the compressed AAC or MP3 audio from the WTV into uncompressed PCM suitable for the AU container's big-endian architecture heritage. |
output.au
|
Sets the output filename with the .au extension, which tells FFmpeg to wrap the pcm_s16be audio stream in a Sun AU container with the standard binary header. The video stream from the WTV is automatically discarded since AU supports only audio. |
Common Use Cases
- Extracting speech or dialogue from a recorded TV broadcast to feed into a Unix-based speech analysis or transcription pipeline that expects raw PCM AU files
- Archiving the audio portion of a Windows Media Center recording in a format compatible with legacy Sun workstation software or classic Unix audio tools like 'play' or 'sox'
- Stripping a recorded TV program's audio track to uncompressed PCM for academic or broadcast research workflows that require format-neutral raw audio
- Preparing audio from a WTV broadcast recording for use in early internet audio streaming contexts or retro computing environments that support the AU format natively
- Converting a recorded TV commentary or radio-over-TV broadcast from WTV to AU for ingestion into scientific signal processing tools such as MATLAB or Audacity on Unix, which have native AU support
- Removing the video from a large WTV DVR file and producing a compact, header-simple AU file for embedding raw audio in Unix shell scripts or piping into command-line audio processors
Frequently Asked Questions
The conversion involves one generation of lossy decode followed by lossless PCM encoding. The original AAC or MP3 audio inside the WTV file is already lossy-compressed, and transcoding to PCM does not recover any detail lost during that original compression. However, the AU output itself introduces no new compression artifacts — pcm_s16be is uncompressed. The final AU file will faithfully represent the audio as it existed in the WTV, without adding further degradation.
The video stream is completely dropped. AU is a strictly audio-only format with no provision for video, subtitles, or chapter data. FFmpeg automatically discards the video track when the output container cannot hold it. If you need to keep the video, you should convert to a format like MP4, MKV, or MOV instead.
The flag '-c:a pcm_s16be' tells FFmpeg to encode the audio as 16-bit signed PCM with big-endian byte ordering, which is the standard encoding expected by the Sun AU format specification. AU was designed on SPARC-based Sun workstations, which use big-endian architecture, so the format inherits big-endian byte order. Using little-endian PCM (as found in WAV files) inside an AU container would produce corrupted audio on compliant AU readers.
Yes. The AU format supports several PCM variants beyond the default pcm_s16be. You can substitute '-c:a pcm_s8' for 8-bit signed PCM, '-c:a pcm_u8' for 8-bit unsigned PCM, '-c:a pcm_alaw' for G.711 A-law encoding (common in telephony), or '-c:a pcm_mulaw' for G.711 mu-law encoding. For example: 'ffmpeg -i input.wtv -c:a pcm_mulaw output.au' produces mu-law encoded AU, which is smaller but lower quality than 16-bit PCM. The 16-bit signed big-endian default offers the best fidelity for general use.
No. The AU format has an extremely minimal header that includes only sample rate, encoding type, channel count, and an optional plain-text annotation field. The rich metadata that WTV embeds — including program title, channel, broadcast timestamp, and EPG data — cannot be stored in AU and will be silently discarded during conversion. If metadata preservation matters, consider extracting it separately with a tool like MediaInfo before converting.
On Linux or macOS, you can use a shell loop: 'for f in *.wtv; do ffmpeg -i "$f" -c:a pcm_s16be "${f%.wtv}.au"; done'. On Windows Command Prompt, use: 'for %f in (*.wtv) do ffmpeg -i "%f" -c:a pcm_s16be "%~nf.au"'. Each WTV file will be processed sequentially, producing a matching AU file with the same base name. Note that AU does not support multiple audio tracks, so only the first (default) audio stream from each WTV file will be extracted.
Technical Notes
WTV is a container format exclusive to Windows Media Center, typically wrapping H.264 video with AAC audio, though MJPEG video and MP3 audio variants exist. AU (Sun Audio) is one of the oldest audio file formats still in use, defined by a simple binary header (magic number 0x2e736e64) followed by uncompressed or lightly encoded audio samples. The default conversion uses pcm_s16be, yielding a bit-for-bit accurate PCM representation of the decoded audio — but file sizes will be significantly larger than the original WTV's compressed AAC audio. For example, a 30-minute stereo AAC stream at 128k in WTV might be around 30MB, whereas the pcm_s16be AU equivalent at 44.1kHz stereo will be approximately 450MB. AU does not support multiple audio tracks, so if your WTV recording contains secondary audio (e.g., a secondary language track or descriptive audio service), only the primary stream will appear in the output. Subtitles and chapter markers from the WTV file are also lost, as AU has no mechanism to carry them. The AU format's streaming-friendly design (stream-length can be set to 0xFFFFFFFF for unknown-length streams) makes it compatible with piping in Unix environments, which is a practical advantage over WAV for certain command-line workflows.