Convert MTS to CAVS — Free Online Tool
Convert MTS camcorder footage (AVCHD format from Sony and Panasonic cameras) to CAVS, the Chinese national broadcast video standard, by re-encoding the H.264 video stream and AC-3/AAC audio into a CAVS-compatible container. This tool runs entirely in your browser using FFmpeg.wasm — no uploads required.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your MTS file here
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Free — no uploads, no signups. Your files never leave your browser.
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
MTS files use the MPEG-2 Transport Stream container carrying H.264 video and typically AC-3 or AAC audio, recorded directly by AVCHD camcorders. Since CAVS uses its own container format designed around the Chinese Audio Video Standard specification, the H.264 video stream cannot simply be remuxed — it must be re-encoded using libx264 targeting CAVS container compatibility. The audio is similarly transcoded to AAC at 128k bitrate. The CRF 23 setting controls the quality-to-filesize tradeoff during re-encoding, producing a lossy output suitable for broadcast workflows that require CAVS compliance.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg media processing tool. In the browser version, this runs as a WebAssembly binary (FFmpeg.wasm) with no server involvement; when run locally, this calls your desktop FFmpeg installation. |
-i input.mts
|
Specifies the input MTS file — an AVCHD MPEG-2 Transport Stream recorded by a Sony or Panasonic camcorder, containing H.264 video and typically AC-3 or AAC audio. |
-c:v libx264
|
Re-encodes the video stream using the libx264 encoder, which is required because the CAVS container only accepts H.264 video. The original H.264 stream from the MTS cannot be directly copied due to container incompatibility. |
-c:a aac
|
Transcodes the audio stream to AAC, which is the only audio codec supported by the CAVS container. If the source MTS contains AC-3 (Dolby Digital) audio from the camcorder, this flag ensures it is converted rather than passed through. |
-crf 23
|
Sets the Constant Rate Factor for libx264 video encoding to 23, the default balance between quality and file size. Lower values (e.g., 18) produce higher-quality CAVS output at larger file sizes, which is recommended for broadcast delivery from high-quality camcorder sources. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second. This is adequate for most converted camcorder audio; increase to 192k or 256k if the source MTS contains high-quality audio that needs to be preserved more faithfully in the CAVS output. |
output.cavs
|
Specifies the output filename with the .cavs extension, which tells FFmpeg to use the CAVS container format for the converted file. |
Common Use Cases
- Preparing Sony or Panasonic camcorder footage for submission to Chinese state broadcast networks or streaming platforms that mandate CAVS-format deliverables
- Archiving AVCHD event recordings (weddings, conferences, corporate productions) in CAVS format for distribution in mainland China markets
- Post-production studios converting raw MTS rushes from camcorders into CAVS for handoff to Chinese broadcast partners or regulatory-compliant VOD platforms
- Government or institutional video producers in China who receive MTS footage from international camera crews and need to normalize it to the national standard before editing or distribution
- Researchers or engineers testing CAVS decoder implementations who need a reliable pipeline from common camcorder source material to CAVS-formatted test vectors
Frequently Asked Questions
Yes, this is a lossy-to-lossy conversion. Your MTS file already contains H.264 video encoded by the camcorder, and re-encoding it to CAVS with libx264 at CRF 23 introduces a second generation of compression loss. To minimize quality degradation, lower the CRF value (e.g., CRF 18) at the cost of a larger output file. For broadcast-critical material, use the highest quality source MTS available and avoid intermediate transcodes before this step.
No. The CAVS container as implemented here only supports AAC audio, so if your MTS file contains AC-3 (Dolby Digital) audio — common on many AVCHD camcorders — it will be transcoded to AAC at 128k. This means multichannel 5.1 AC-3 audio from your camcorder will be converted to stereo AAC unless you explicitly configure channel mapping in the FFmpeg command. Check your source MTS audio track before conversion if preserving surround sound is important.
No. CAVS does not support multiple audio tracks, so FFmpeg will include only the default (typically first) audio track from the MTS source. If your AVCHD recording contains a secondary audio track — for example, from a dual-channel microphone setup or a mixed language track — it will be silently dropped during conversion. Use FFmpeg's -map flag locally to explicitly select which audio track to include.
No. Although MTS files can carry subtitle streams, the CAVS container does not support subtitles. Any subtitle data embedded in the source MTS will be discarded during conversion. If your footage contains burned-in on-screen text (hardcoded subtitles as part of the video frame), those will naturally survive since they are part of the video image itself.
Change the -crf value to control video quality: lower numbers (e.g., -crf 18) mean higher quality and larger files, while higher numbers (e.g., -crf 28) produce smaller files with more compression. Adjust audio quality by changing the -b:a value, for example -b:a 192k for higher fidelity audio. The full modified command would look like: ffmpeg -i input.mts -c:v libx264 -c:a aac -crf 18 -b:a 192k output.cavs
The browser tool processes one file at a time, but if you have many MTS files over 1GB or want to automate batch conversion on your desktop, you can adapt the FFmpeg command in a shell loop. On Linux or macOS: for f in *.mts; do ffmpeg -i "$f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "${f%.mts}.cavs"; done. On Windows PowerShell: Get-ChildItem *.mts | ForEach-Object { ffmpeg -i $_.Name -c:v libx264 -c:a aac -crf 23 -b:a 128k ($_.BaseName + '.cavs') }
Technical Notes
CAVS (Chinese Audio Video Standard, also known as AVS or GB/T 20090) is a Chinese national standard primarily deployed in domestic broadcast and digital television infrastructure. The CAVS container has strict codec constraints — only libx264 video and AAC audio are supported in this implementation, which means the rich codec flexibility of the MTS/AVCHD source (including potential H.265/HEVC or AC-3 tracks) is flattened on output. Notably, CAVS does not support chapters, multiple audio tracks, or subtitle streams, so any of these present in your AVCHD source will be lost without warning. The MPEG-2 Transport Stream structure of MTS files, which was designed for broadcast resilience and supports discontinuous streams, is completely discarded — the CAVS output is a self-contained file. Timestamp handling can occasionally be an issue with MTS files from consumer camcorders that contain PTS discontinuities; if you encounter sync problems, adding -fflags +genpts to the FFmpeg command before the input flag can help FFmpeg regenerate clean timestamps. File sizes will vary significantly depending on the CRF setting and the motion complexity of your camcorder footage.