Convert CAVS to AC3 — Free Online Tool
Extract and convert the AAC audio track from a CAVS video file into Dolby Digital AC3 format, producing a standard .ac3 file encoded at 192kbps using the ac3 codec. This is particularly useful for integrating Chinese broadcast content audio into DVD authoring pipelines or home theater systems that require Dolby Digital compatibility.
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FFmpeg Command
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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 contain a video stream encoded with H.264 (libx264) and an audio stream encoded with AAC. Since AC3 is a pure audio container format, the video stream is completely discarded during this conversion — FFmpeg extracts only the AAC audio from the CAVS container and re-encodes it using the Dolby Digital AC3 codec at 192kbps. This is a full transcode of the audio: the AAC bitstream is decoded to raw PCM audio and then re-encoded into AC3, which means this is a lossy-to-lossy conversion. The resulting .ac3 file contains only the Dolby Digital audio stream with no video, subtitles, or chapters — none of which are supported by the AC3 format.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, the open-source multimedia processing engine that handles demuxing the CAVS container, decoding the AAC audio, re-encoding to AC3, and writing the output file. |
-i input.cavs
|
Specifies the input file — a CAVS-format video file containing an H.264 video stream and an AAC audio stream. FFmpeg will demux both streams, but only the audio will be used in this conversion. |
-c:a ac3
|
Instructs FFmpeg to encode the output audio using the Dolby Digital AC3 codec. The AAC audio decoded from the CAVS file is re-encoded as AC3, which is the standard format for Dolby Digital audio on DVDs, Blu-rays, and broadcast television. |
-b:a 192k
|
Sets the AC3 audio bitrate to 192 kilobits per second. This is a standard bitrate for stereo Dolby Digital audio; for multichannel surround content from the CAVS source, a higher value like 384k or 448k would better preserve audio fidelity across all channels. |
output.ac3
|
Specifies the output file as a raw AC3 audio stream file. The .ac3 extension tells FFmpeg to write a bare Dolby Digital bitstream with no container wrapper, suitable for DVD authoring tools, AV receivers, and broadcast systems that consume raw AC3 audio. |
Common Use Cases
- Extracting the audio from CAVS broadcast recordings for authoring onto DVDs that require Dolby Digital AC3 audio tracks
- Converting CAVS-encoded Chinese television content audio into AC3 for playback on AV receivers and home theater systems with Dolby Digital decoders
- Preparing audio from CAVS media files for integration into video editing timelines that require AC3 as a deliverable audio format
- Archiving the audio component of CAVS broadcast content in the widely supported AC3 format for long-term compatibility with DVD and Blu-ray players
- Stripping and converting audio from CAVS files for use as surround-sound-compatible audio assets in broadcast post-production workflows
Frequently Asked Questions
Yes, some quality loss is inevitable. The source CAVS file contains AAC audio, which is already a lossy format. Converting to AC3 requires decoding that AAC audio to raw PCM and then re-encoding it using the Dolby Digital codec — a second generation of lossy compression. At 192kbps AC3, the result is generally acceptable for broadcast and home theater use, but if the source AAC was encoded at a low bitrate (e.g., 64k or 96k), artifacts from the original encoding may become more noticeable after the transcode.
That depends entirely on the audio content in the source CAVS file. AC3 is capable of encoding up to 5.1 surround sound, but if the AAC audio track in your CAVS file is stereo or mono, the resulting AC3 file will also be stereo or mono. FFmpeg will preserve the channel layout of the source audio during re-encoding. If you need a specific channel configuration, you would need to add a channel mapping flag to the FFmpeg command.
This tool converts specifically to the AC3 raw audio format, which is a standalone audio stream file used in DVD authoring tools, broadcast systems, and AV receivers. If you want an MP4 or MKV file with Dolby Digital audio, you would need a video-to-video conversion tool that rewraps or re-encodes the video alongside an AC3 audio track. The .ac3 output from this tool contains no video data.
Change the value after the -b:a flag in the command. AC3 supports bitrates from 96k up to 640k — for example, use -b:a 384k for higher quality output or -b:a 128k to reduce file size. Note that 192k is the default and is suitable for stereo content, while 5.1 surround tracks typically require at least 384k or 448k to sound their best. Replace 192k with your chosen bitrate: ffmpeg -i input.cavs -c:a ac3 -b:a 384k output.ac3
Yes, on the command line you can use a shell loop to process multiple files. On Linux or macOS, run: for f in *.cavs; do ffmpeg -i "$f" -c:a ac3 -b:a 192k "${f%.cavs}.ac3"; done. On Windows Command Prompt, use: for %f in (*.cavs) do ffmpeg -i "%f" -c:a ac3 -b:a 192k "%~nf.ac3". The in-browser tool processes one file at a time, so the FFmpeg command is especially useful for batch operations on large collections of CAVS files.
CAVS (Chinese Audio Video Standard) is a Chinese national broadcast standard and is relatively uncommon outside of China. FFmpeg includes a CAVS demuxer and can read properly formed CAVS files, but files produced by certain proprietary Chinese broadcast encoders may have non-standard headers that can cause compatibility issues. If FFmpeg reports an error reading your CAVS file, the file may be malformed or use a non-standard CAVS variant not fully supported by the libavformat demuxer.
Technical Notes
This conversion discards the H.264 video stream entirely and performs a full audio transcode from AAC (as found in CAVS containers) to Dolby Digital AC3. Because both AAC and AC3 are lossy codecs, the conversion involves two generations of lossy compression, which is an inherent quality penalty compared to transcoding from a lossless source. The AC3 codec in FFmpeg (the native ac3 encoder) is a solid implementation of the Dolby Digital standard and produces output compatible with DVD players, Blu-ray players, AV receivers, and broadcast systems. The AC3 format does not support metadata such as chapter markers, embedded subtitles, or multiple audio tracks — all of which are also unsupported by the CAVS source format, so no metadata is lost that would otherwise be preserved. The default 192kbps bitrate is appropriate for stereo content; for 5.1 surround audio sourced from a multichannel CAVS file, consider raising the bitrate to 384k or higher to maintain acceptable quality across all six channels.