Convert CAVS to WTV — Free Online Tool
Convert CAVS (Chinese Audio Video Standard) files to WTV (Windows Television) format, re-encoding video with H.264 via libx264 and audio with AAC — producing a DVR-compatible container recognized by Windows Media Center with support for multiple audio tracks and subtitle streams.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your CAVS 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
CAVS files use a Chinese national standard video codec that is not natively supported by most Western software or DVR systems. During this conversion, FFmpeg decodes the CAVS video stream and re-encodes it as H.264 using libx264, while the audio is transcoded to AAC at 128k bitrate. The output is wrapped in the WTV container, a Microsoft format designed for Windows Vista Media Center and later DVR applications. Because CAVS video must be fully decoded and re-encoded (not remuxed), this is a full transcode operation — every frame is decompressed and compressed again using the H.264 CRF 23 quality setting. The resulting WTV file gains compatibility with Windows Media Center, supports metadata embedding, and can carry multiple audio tracks — features the source CAVS format does not offer.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg application — in this browser-based tool, it runs as FFmpeg.wasm compiled to WebAssembly, executing entirely within your browser with no server upload required. |
-i input.cavs
|
Specifies the input file in CAVS format. FFmpeg detects the AVS1-P2 video codec and the associated audio stream, decoding them internally before the re-encoding stage. |
-c:v libx264
|
Sets the video encoder to libx264, which re-encodes the decoded CAVS video frames as H.264. H.264 is the standard video codec for WTV files and ensures compatibility with Windows Media Center and other Windows media playback tools. |
-c:a aac
|
Transcodes the audio stream to AAC, the default audio codec for WTV output. AAC provides efficient compression at broadcast-quality bitrates and is well-supported by Windows media infrastructure. |
-crf 23
|
Controls H.264 video quality using Constant Rate Factor mode. A value of 23 is the libx264 default, delivering a good balance of visual quality and file size. Lower values (e.g., 18) improve quality for detail-rich CAVS content; higher values (e.g., 28) reduce file size at the cost of visible compression artifacts. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second, which is appropriate for mono or stereo broadcast audio typical of CAVS source material. Increase to 192k or 256k if the source contains high-quality stereo or surround audio worth preserving. |
output.wtv
|
Defines the output filename and tells FFmpeg to use the WTV container format based on the .wtv file extension. FFmpeg selects the WTV muxer automatically, wrapping the H.264 video and AAC audio into the Windows Television structured storage format. |
Common Use Cases
- Archiving Chinese broadcast recordings originally captured in CAVS format into a Windows Media Center library for organized DVR-style playback
- Preparing CAVS video content for playback on Windows Home Theater PCs (HTPCs) that use Windows Media Center as their primary interface
- Converting CAVS news or documentary footage into WTV so it can be catalogued alongside other recorded TV content with embedded broadcast metadata
- Migrating a collection of CAVS-encoded Chinese television episodes into WTV for long-term storage in a format that remains accessible via standard Windows media tools
- Transcoding CAVS video to WTV to take advantage of WTV's multiple audio track support — for example, adding a dubbed audio stream alongside the original Chinese audio
- Converting CAVS content for editing workflows that accept WTV input, since H.264-in-WTV is more widely recognized by Windows-based video editors than raw CAVS streams
Frequently Asked Questions
Yes, some quality loss is inevitable because CAVS video must be fully decoded and re-encoded as H.264 — there is no lossless remux path between these two formats. The default CRF value of 23 produces visually good results for most content, striking a balance between file size and quality. If you need higher fidelity, you can lower the CRF value (e.g., to 18) in the FFmpeg command, which increases quality at the cost of a larger output file.
WTV is a Microsoft container designed around codecs common to Windows broadcast workflows, primarily H.264, MPEG-2, and MJPEG. The CAVS codec (AVS1-P2) is a Chinese national standard not supported as a native WTV video codec, so FFmpeg cannot simply copy the raw bitstream into the WTV wrapper. The video must be decoded from CAVS and re-encoded into a codec the WTV container actually supports, which is why libx264 is used here.
WTV does support subtitle streams, but since CAVS files typically do not carry subtitle data, no subtitle tracks will be present in the output file. If you have an external subtitle file (such as an SRT), you can modify the FFmpeg command to include it — for example, adding '-i subtitles.srt -c:s copy' before the output filename — to embed subtitles into the WTV file during the same conversion pass.
To adjust video quality, change the '-crf 23' value: lower numbers (e.g., 18) produce higher quality and larger files, while higher numbers (e.g., 28 or 35) reduce quality but shrink the file size. CRF 0 is mathematically lossless for H.264. To change audio quality, replace '128k' in '-b:a 128k' with your preferred bitrate, such as '192k' or '256k' for better audio fidelity, or '96k' to reduce file size — useful if the source CAVS audio was originally low-bitrate broadcast audio.
Yes. On Windows, you can use a simple batch script: 'for %f in (*.cavs) do ffmpeg -i "%f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "%~nf.wtv"'. On Linux or macOS, the equivalent is: 'for f in *.cavs; do ffmpeg -i "$f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "${f%.cavs}.wtv"; done'. This is especially useful for large CAVS archives since the browser-based tool handles one file at a time, while the desktop command processes an entire folder.
In most cases, yes — WTV files placed in the Windows Media Center recorded TV library folder are recognized automatically. However, metadata such as show title, episode information, and channel data that would normally be embedded during a live TV recording will not be present in a file converted from CAVS. Windows Media Center may display the file with generic or missing metadata. WTV's metadata embedding features can be populated with third-party tools after conversion if accurate program guide data is needed.
Technical Notes
CAVS (AVS1-P2) is a Chinese national video coding standard developed by the Audio Video coding Standard Workgroup of China and was promoted as a lower-royalty alternative to H.264 for Chinese broadcast and optical disc applications. Because it has limited adoption outside China, CAVS files are rarely supported by Western media software, which makes transcoding to a more universal codec essential for broader compatibility. The WTV container was introduced with Windows Vista Media Center and is essentially a structured storage format (based on Microsoft's compound document format) wrapping MPEG-style audio/video streams with rich DVR metadata. This conversion uses libx264 for H.264 encoding with CRF-based quality control, meaning the bitrate adapts to scene complexity rather than being fixed — complex CAVS content with high motion will result in larger WTV files than static content at the same CRF. Neither CAVS nor WTV supports transparency, and chapters are not preserved in this conversion. WTV does support multiple audio tracks, which opens the door to adding additional language tracks post-conversion. One known limitation: FFmpeg's WTV muxer support is functional but less mature than its MP4 or MKV muxers, so some advanced WTV metadata fields may not be fully populated.