Convert M2TS to CAVS — Free Online Tool
Convert M2TS Blu-ray and AVCHD files to CAVS format using H.264 video and AAC audio, processed entirely in your browser. This tool is particularly useful for adapting high-definition Blu-ray content to China's national broadcast video standard without needing desktop software.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your M2TS 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
M2TS files typically contain H.264 or MPEG-2 video alongside multi-channel audio (often AC-3, DTS, or TrueHD) wrapped in an MPEG-2 Transport Stream. During this conversion, the video stream is re-encoded to H.264 (libx264) regardless of the source codec, since CAVS containers only support H.264 video. The audio — which in M2TS files frequently includes lossless or multi-channel formats incompatible with CAVS — is transcoded to stereo AAC at 128k. Critically, CAVS does not support subtitles, chapters, or multiple audio tracks, so any subtitle streams, secondary audio tracks, or chapter markers present in the M2TS source will be dropped during conversion. The result is a single-track, subtitle-free CAVS file suitable for broadcast or distribution within Chinese-standard ecosystems.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, which is running here as a WebAssembly (FFmpeg.wasm) instance entirely within your browser — no files leave your device during this conversion. |
-i input.m2ts
|
Specifies the input file in M2TS format — an MPEG-2 Transport Stream container as used on Blu-ray discs and AVCHD camcorders, which may contain H.264 or MPEG-2 video, multi-channel lossless audio, PGS subtitles, and multiple audio tracks. |
-c:v libx264
|
Re-encodes the video stream using the libx264 H.264 encoder, which is the only video codec supported by the CAVS container in FFmpeg. This step is always performed regardless of whether the M2TS source already contains H.264 video. |
-c:a aac
|
Transcodes the audio to AAC, the only audio codec supported by the CAVS container. This replaces any lossless or multi-channel audio from the M2TS source (such as DTS-HD or TrueHD) with a stereo lossy AAC stream. |
-crf 23
|
Sets the Constant Rate Factor for H.264 encoding to 23, which is the default balance point between visual quality and file size. Lower values (e.g., 18) produce higher quality at larger file sizes; higher values (e.g., 28) compress more aggressively. Given that M2TS Blu-ray sources are high-bitrate, CRF 18–20 may be preferable for preserving more of the original visual detail. |
-b:a 128k
|
Sets the AAC audio output bitrate to 128 kilobits per second, a standard lossy quality level for stereo audio. Since M2TS files frequently carry lossless or high-bitrate surround audio, this represents a significant downgrade in audio fidelity — increase to 192k or 256k if audio quality is a priority. |
output.cavs
|
Defines the output filename with the .cavs extension, which tells FFmpeg to use the CAVS muxer to wrap the re-encoded H.264 video and AAC audio into a Chinese Audio Video Standard container file. |
Common Use Cases
- Preparing Blu-ray rip footage in M2TS format for submission to Chinese broadcast platforms that require CAVS-compliant files
- Converting AVCHD camcorder footage captured in M2TS to CAVS for editing or distribution within Chinese media production workflows
- Stripping down a multi-track, multi-subtitle M2TS file to a simple single-stream CAVS file for lightweight archiving or sharing
- Testing CAVS container compatibility with H.264-encoded content originally mastered from Blu-ray sources
- Adapting high-definition M2TS video content for playback on legacy Chinese set-top boxes or media players that require CAVS format
- Generating a CAVS reference file from a Blu-ray M2TS source to verify encoder output quality before a larger batch conversion on desktop FFmpeg
Frequently Asked Questions
No — CAVS does not support subtitles or multiple audio tracks at the container level. The conversion will retain only the first (primary) audio track and discard all subtitle streams, secondary audio tracks, and chapter data that may be present in your M2TS source. If preserving subtitles or alternate audio is important, CAVS is not an appropriate target format for that content.
Lossless and multi-channel audio formats like DTS-HD Master Audio or Dolby TrueHD found in M2TS files cannot be carried into a CAVS container. During conversion, the audio is fully transcoded to AAC stereo at 128k bitrate. This introduces lossy compression and downmixes surround channels to stereo, so some fidelity from the original Blu-ray audio will be lost. If you need to preserve the original audio quality, this conversion is not suitable.
It depends on the source. If your M2TS contains H.264 video, re-encoding it to H.264 again at CRF 23 introduces a generation of compression loss — the output will not be identical to the source. If the source uses MPEG-2 or VC-1 (also common in M2TS files), the re-encode to H.264 at CRF 23 may actually produce a comparable or smaller file while maintaining acceptable visual quality. For high-quality preservation, lower CRF values (e.g., 18) will produce better results at the cost of a larger file.
To improve video quality, lower the CRF value — replace '-crf 23' with '-crf 18' for higher quality (larger file) or '-crf 28' for smaller file size with reduced quality. CRF 0 is lossless H.264, while CRF 51 is the lowest quality. To change audio bitrate, replace '-b:a 128k' with a value like '-b:a 192k' or '-b:a 256k' for better audio fidelity. For example: ffmpeg -i input.m2ts -c:v libx264 -c:a aac -crf 18 -b:a 192k output.cavs
Yes. On Linux or macOS, you can use a shell loop: for f in *.m2ts; do ffmpeg -i "$f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "${f%.m2ts}.cavs"; done. On Windows Command Prompt, use: for %f in (*.m2ts) do ffmpeg -i "%f" -c:v libx264 -c:a aac -crf 23 -b:a 128k "%~nf.cavs". This is especially useful for M2TS files over 1GB, which exceed the browser tool's limit and must be processed locally.
CAVS (Chinese Audio Video Standard) is a video codec and container standard developed by China as a domestic alternative to internationally licensed formats like H.264/AVC. It is used primarily within Chinese broadcast, cable television, and media distribution infrastructure. Despite its name implying a native Chinese codec, current FFmpeg CAVS container support wraps H.264 video and AAC audio — the CAVS video codec (AVS1/AVS2) itself has limited open-source encoder support. This makes the format niche outside of Chinese media industry contexts.
Technical Notes
The CAVS container is a niche format with limited codec flexibility — FFmpeg's CAVS muxer supports only H.264 video and AAC audio, making the re-encoding of M2TS content mandatory regardless of what codecs the source uses. M2TS files from Blu-ray discs often carry MPEG-2 or H.264 video alongside lossless multi-channel audio (TrueHD, DTS-HD MA) and multiple subtitle tracks (PGS format); all of this richness is lost in the CAVS container, which supports none of it. The output is strictly lossy — CAVS has no lossless encoding path. File size compared to the M2TS source will vary significantly: Blu-ray M2TS files often have very high bitrates (20–40 Mbps), and re-encoding to H.264 at CRF 23 typically produces a much smaller output file, often at a fraction of the original size. Because CAVS is not a mainstream container, playback support outside of specialized Chinese broadcast players is limited — most general-purpose media players and streaming platforms do not natively support .cavs files, so this conversion is intended for specific professional or compliance use cases rather than general distribution.