Extract Audio from CAVS to WMA — Free Online Tool
Extract audio from CAVS (Chinese Audio Video Standard) video files and convert it to WMA format using the wmav2 codec — ideal for repurposing broadcast-grade Chinese video content into Windows-compatible audio files. The conversion strips the video stream entirely and re-encodes the AAC audio track to Windows Media Audio at 128k bitrate by default.
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 AAC audio paired with a Chinese-standard video codec (libx264-based). This tool discards the video stream completely using the -vn flag and re-encodes the AAC audio track to WMA using the wmav2 codec. Because AAC and WMA are both lossy formats with different compression algorithms, the audio must be fully decoded and re-encoded — it cannot be stream-copied. This means there is a small, unavoidable generation loss as the audio moves from one lossy codec to another. The resulting .wma file is a pure audio container with no video data, compatible with Windows Media Player, legacy Windows devices, and Microsoft ecosystem tools.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, which is running here as FFmpeg.wasm compiled to WebAssembly and executing entirely within your browser — no data leaves your machine. |
-i input.cavs
|
Specifies the input file in CAVS format. FFmpeg reads the CAVS container and identifies the video stream (libx264) and audio stream (AAC) inside it. |
-vn
|
Disables video output entirely, instructing FFmpeg to ignore the libx264 video stream in the CAVS file. This is essential because WMA is an audio-only format and cannot contain video data. |
-c:a wmav2
|
Sets the audio codec to wmav2 (Windows Media Audio version 2), which re-encodes the AAC audio from the CAVS source into the WMA format. wmav2 is the default and higher-quality WMA codec, preferred over the older wmav1. |
-b:a 128k
|
Sets the WMA audio output bitrate to 128 kilobits per second. This is a standard bitrate for WMA files that balances file size and audio quality well for both speech and music extracted from broadcast CAVS content. |
output.wma
|
Specifies the output filename with a .wma extension. FFmpeg uses this extension to confirm the ASF/WMA container format, which holds the wmav2-encoded audio stream. |
Common Use Cases
- Extracting speech or commentary audio from CAVS broadcast recordings for archival in Windows Media Player libraries
- Converting Chinese national broadcast CAVS content to WMA for playback on older Windows CE or Windows Mobile devices that natively support WMA but not AAC
- Preparing audio from CAVS video files for use in Windows-based media workflows or SharePoint media libraries that favor WMA delivery
- Stripping the audio from CAVS video files to create standalone audio tracks for Mandarin language learning materials on Windows platforms
- Extracting interview or documentary audio from CAVS broadcast recordings to distribute as WMA streams over legacy Windows Media Services
- Converting CAVS audio to WMA to leverage WMA's DRM support for protecting licensed Chinese broadcast audio content in Windows environments
Frequently Asked Questions
Yes, some quality loss is unavoidable. Both AAC (used in CAVS files) and WMA (wmav2) are lossy codecs, so converting between them requires a full decode-and-re-encode cycle rather than a lossless stream copy. The degree of quality loss depends on the original AAC bitrate and the target WMA bitrate — using a higher -b:a value (e.g., 192k or 256k) for the WMA output will minimize the impact. At matched bitrates, AAC generally has a slight technical efficiency advantage over wmav2, so the WMA output may sound marginally different even at the same bitrate.
This tool is specifically designed to extract audio only. The -vn flag in the FFmpeg command explicitly disables video output, resulting in a pure WMA audio file. WMA is an audio-only container format and cannot hold a video stream, so even if you removed the -vn flag, FFmpeg would still produce an audio-only output. If you need to retain the video, you would need a different tool that converts CAVS to a video container format.
WMA (via the ASF container) supports a rich set of metadata tags including title, artist, album, and genre. FFmpeg will attempt to map metadata from the CAVS source to the WMA output automatically, but CAVS files from broadcast sources may carry limited or non-standard metadata. You can verify or add tags using the -metadata flag in the FFmpeg command locally (e.g., -metadata title='My Track'). The wmav2 codec itself does not strip metadata — any loss would come from the source file having none to begin with.
Modify the -b:a value in the command. For example, replace 128k with 192k for higher quality: ffmpeg -i input.cavs -vn -c:a wmav2 -b:a 192k output.wma. WMA supports bitrates from 64k up to 320k — lower values like 64k or 96k produce smaller files suitable for speech, while 192k–320k is better for music extracted from broadcast CAVS content. The default 128k is a reasonable balance for most voice and mixed-content audio.
Yes. Replace -c:a wmav2 with -c:a wmav1 in the command: ffmpeg -i input.cavs -vn -c:a wmav1 -b:a 128k output.wma. WMA v1 (wmav1) is an older codec supported by the earliest Windows Media Player versions and certain legacy hardware players. However, wmav2 is generally preferred because it offers better audio quality at the same bitrate and is still universally supported on Windows platforms. Only use wmav1 if you specifically need compatibility with very old Windows 98-era software or hardware.
The command shown processes one file at a time, but you can adapt it for batch processing on your desktop. On Linux or macOS, use a shell loop: for f in *.cavs; do ffmpeg -i "$f" -vn -c:a wmav2 -b:a 128k "${f%.cavs}.wma"; done. On Windows Command Prompt: for %f in (*.cavs) do ffmpeg -i "%f" -vn -c:a wmav2 -b:a 128k "%~nf.wma". The browser-based tool processes files individually, so for large batches the local FFmpeg command approach is significantly more efficient.
Technical Notes
CAVS files encode audio as AAC, typically at broadcast-standard bitrates, within a container associated with the Chinese Audio Video Standard — a format developed for Chinese national broadcasting and not widely supported outside that ecosystem. When extracting to WMA, FFmpeg uses the wmav2 encoder, which implements Windows Media Audio version 2 inside an ASF (Advanced Systems Format) container. The ASF container supports DRM, metadata tagging, and streaming markers, making WMA a practical choice for Windows-centric distribution pipelines. One important limitation: WMA files do not support multiple audio tracks, so if the CAVS source had multiple audio streams (uncommon but possible in broadcast content), only the default stream will be extracted. WMA also does not support chapter markers or subtitle embedding, though neither is typically present in audio-extracted workflows. The wmav2 codec performs best at bitrates of 128k and above; at 64k, artifacts may become noticeable especially on music content, though speech extracted from broadcast CAVS recordings typically remains intelligible at lower bitrates.