WTV to AU Converter

How to Convert WTV to AU Online

1. Upload Your WTV File: Drag and drop or click "+ Add Files" to load .wtv recordings from Windows Media Center. Batch upload is supported — process a season's worth of recordings in one pass. 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.
2. Pick Audio Channel and Sample Rate: Default is Original for both — the converter preserves whatever the WTV stream carries. Switch Audio Channel to Mono for telephony-grade AU files compatible with legacy Java AudioSystem and Unix workstations. Set Audio Sample Rate to 8000 Hz for classic G.711 µ-law output, 22050 Hz for compact voice archives, or 44100 Hz to keep CD-quality fidelity.
3. Trim Before Encoding (Optional): Use Trim to clip commercials, intros, or station IDs out of recorded broadcasts before extraction. Set start time in HH:MM:SS.ms and either an end time or a duration, so you only encode the segment you actually need.
4. Convert and Download: Click "Convert" and grab each AU file individually or as a ZIP. No sign-up, no watermark, no email gating.

Why Convert WTV to AU?

WTV is Microsoft's container for Windows Media Center recordings — MPEG-2 or MPEG-4 video plus MPEG-1 Layer II or Dolby Digital AC-3 audio, introduced with the Windows Media Center TV Pack 2008 for Windows Vista and standard on every Windows 7 Media Center edition. Microsoft dropped Media Center from Windows 10 in 2015 and the Electronic Program Guide service shut down on January 14, 2020, so old WTV archives are increasingly orphaned on machines that can't play them. AU (Sun Audio, also called NeXT/Sun .au) is the audio-only counterpart — a 24-byte big-endian header followed by a single audio stream, with µ-law, A-law, or linear PCM payload. Pulling the audio out of a WTV recording into AU is a useful step when you only need the soundtrack:

• Java applications and applets — javax.sound.sampled.AudioSystem reads and writes AU natively without external codecs, making it the path of least resistance for any JVM-based audio playback, voice-prompt system, or unit-test fixture.
• Telephony and IVR prompts — Asterisk, FreeSWITCH, and many legacy PBX platforms accept 8 kHz mono µ-law .au directly. Convert a recorded interview, news segment, or training clip into a hold-music or IVR greeting in a single pass.
• Unix and academic archives — University speech corpora, NIST sample databases, and older SPARC/Solaris software still ship .au. Matching the format keeps tooling like sox, play, and audacity happy without container conversion.
• Long-term audio preservation — A 24-byte header with no nested chunks is friction-free for forensic and archival workflows that prefer formats that survive bit-rot or partial recovery better than complex containers.
• Stripping video to save space — A 30-minute WTV recording at 8 Mbps weighs ~1.8 GB; the same audio as 8 kHz mono µ-law AU is ~14 MB — a 99% reduction when you only care about the voice track.
• Compliance and accessibility — Generating an audio-only version of a broadcast for screen-reader workflows, transcription pipelines, or accessibility archives where the video isn't needed.

Working with the original recording first? Convert WTV to MP4 to keep video, or pull a lossless audio track with WTV to WAV. Need the reverse direction or a different audio codec? See WAV to AU and MP3 to AU, or trim the result with Audio Cutter.

WTV vs AU — Container Comparison

AU Encoding Quick Guide

.au is a multi-codec container — the choice of encoding affects file size and downstream compatibility more than the .au extension itself. xConvert exposes µ-law, A-law, and signed PCM variants for AU output via Audio Codec selection where supported.

For most "play this in a Java app or IVR" workflows, stick with 8 kHz mono µ-law — it's the codec the AU container was originally designed around (G.711 µ-law has been the ITU-T telephony reference since 1972, with audio passed in the 300–3400 Hz voice band).

Frequently Asked Questions

Why convert WTV to AU instead of MP3 or WAV?

Pick AU when downstream tooling specifically wants it: javax.sound.sampled in Java reads .au natively without an external decoder, many legacy Asterisk/FreeSWITCH prompt directories expect 8 kHz µ-law .au, and older Solaris/NeXT audio archives use it as the lingua franca. For general-purpose listening on phones or in browsers, WTV to MP3 is the friendlier choice; for lossless editing, use WTV to WAV. AU's niche is Unix/Java/telephony — that's where it earns its place.

What's the default AU encoding if I don't change anything?

xConvert encodes AU with 16-bit linear PCM by default when the source has music or wide-band audio (which most WTV broadcasts do), preserving fidelity. Set Audio Sample Rate to 8000 Hz and Audio Channel to Mono if you specifically need the classic 8-bit µ-law telephony profile — that combination yields the smallest, most-compatible "legacy AU" output. The original Sun headerless .au was always 8-bit µ-law at 8 kHz; modern AU adds the 24-byte header so the encoding can be specified explicitly.

Will the AC-3 5.1 surround track in my WTV recording collapse to mono?

Broadcast WTV recordings commonly carry Dolby Digital AC-3 with up to 5.1 channels. If you leave Audio Channel on Original, AU stores whatever channel count the source has (mono, stereo, or multichannel). If you set it to Mono, the converter downmixes all channels into one, which is what you want for telephony or IVR prompts. For stereo music preservation, leave it on Original and pick 16-bit PCM at 44100 Hz or 48000 Hz.

Why is AU big-endian when Windows is little-endian?

AU was designed at Sun Microsystems for SPARC and shipped widely on NeXT — both 1980s/early-1990s big-endian architectures — and the header was deliberately laid out in network byte order so files could be streamed across early Internet links without per-host conversion. WAV, by contrast, was specified by Microsoft and IBM for x86 PCs and is little-endian. xConvert handles the byte-order flip during encoding; you don't need to think about it, but it's the reason a raw cat of an .au file shows .snd followed by readable big-endian integers in a hex dump.

Can my browser play the resulting AU file?

Patchy. Firefox and Chrome have historically supported audio/basic (the AU MIME type) through Web Audio decoding, but it depends on the encoding inside — 8-bit µ-law at 8 kHz is the most likely to play. 16-bit PCM AU files often don't play in browsers without conversion to WAV. If browser playback matters, convert to MP3 or WAV instead. AU's strength is server-side, JVM, or native-app playback, not modern browser usage.

Is Windows Media Center still required to read my WTV files?

No. xConvert reads WTV on our servers via ffmpeg without needing Windows Media Center installed — useful because Microsoft removed Media Center from Windows 10 in 2015 and the Electronic Program Guide service ended on January 14, 2020. Open-source tools like ffmpeg (which the conversion pipeline uses under the hood) parse the proprietary container directly. Note: a small number of WTV recordings carry CableCARD-protected DRM and will fail to decode anywhere outside the recording PC — that's the broadcast flag, not a converter limitation.

Should I pick µ-law or A-law?

If the audio is destined for a North American or Japanese telephony system (Asterisk in NANP territory, US/Japan IVR vendors), pick µ-law — it's the default for the public switched telephone network in those regions. If the destination is European or ITU-aligned (most of Africa, Asia outside Japan, Latin America's PSTNs), pick A-law. Both are 8-bit companded at 64 kbit/s; the difference is the compression curve, and audio encoded for the wrong region will sound slightly noisier on the matched hardware. For archival or non-telephony use, either works equally well.

Does the conversion preserve broadcast metadata like the show title, channel, and recording date?

The WTV container stores Electronic Program Guide metadata (title, episode, channel, broadcast date) outside the audio stream. AU's optional info chunk after the 24-byte header can hold a short ASCII description, and xConvert writes a brief annotation there when source metadata is available, but EPG details don't have a structured equivalent in AU. If preserving full metadata matters, keep a sidecar .txt of the source filename or convert to a metadata-rich format like FLAC or MP3 (with ID3) instead.

How does the file size compare to the original WTV?

Dramatic shrinkage. A 30-minute WTV recording at typical broadcast bitrates (~8 Mbps total, ~256 kbps audio) is around 1.8 GB. The same audio as 8 kHz mono µ-law AU is roughly 14 MB — about 0.8% of the source. As 16-bit stereo PCM AU at 44.1 kHz it's around 300 MB, which is closer to the WAV equivalent. The video stream is what dominates WTV size; extracting any audio-only format will recover most of the space.