MyMediaTools

Convert CAVS to VOB — Free Online Tool

Convert CAVS (Chinese Audio Video Standard) files to VOB format, re-encoding the video to MPEG-2 and audio to Dolby AC3 — the exact codec pair required for DVD-Video disc compatibility. Useful for bringing Chinese broadcast content into DVD authoring workflows.

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How It Works

CAVS files typically use an AVS/AVS2 video stream with AAC audio, neither of which are supported inside the VOB container. This conversion performs a full re-encode: the video is decoded from its CAVS-standard codec and re-encoded as MPEG-2 video using the mpeg2video encoder, while the audio is transcoded from AAC to Dolby AC3 at 192k bitrate. The output is wrapped in the VOB container with the mandatory '-f vob' flag, which structures the bitstream as a DVD-Video object. Because both the video and audio streams are re-encoded, processing time is longer than a simple remux, and some generation loss occurs — though the default quality settings (q:v 4 for video, 192k for AC3 audio) are well-suited for standard-definition DVD output.

What Each Flag Does

Flag What it does
ffmpeg Invokes the FFmpeg binary. This entire conversion runs locally in your browser via FFmpeg.wasm (WebAssembly) — no data is sent to a server — or can be run on your desktop CLI for files over 1GB.
-i input.cavs Specifies the input file in CAVS format. FFmpeg uses its built-in CAVS decoder to read the Chinese Audio Video Standard video stream and its associated audio.
-c:v mpeg2video Re-encodes the video stream using FFmpeg's MPEG-2 encoder (mpeg2video), which is the mandatory video codec for DVD-Video compatible VOB files. The CAVS video is fully decoded and compressed again as MPEG-2.
-c:a ac3 Transcodes the audio from the CAVS source's AAC stream to Dolby AC3, the standard audio codec for DVD-Video. AC3 is required for compatibility with standalone DVD players and most DVD authoring applications.
-q:v 4 Sets the MPEG-2 video quality using the variable quantizer scale, where 1 is highest quality and 31 is lowest. A value of 4 produces high-quality MPEG-2 output well-suited for DVD authoring, balancing file size against visual fidelity.
-b:a 192k Sets the AC3 audio output bitrate to 192 kilobits per second, a standard bitrate for stereo Dolby Digital on DVD that provides clean audio reproduction without excessive disc space usage.
-f vob Forces the output container format to VOB (DVD Video Object), structuring the MPEG Program Stream with the specific packet layout expected by DVD players and authoring tools, rather than a generic MPEG-PS file.
output.vob The output filename with the .vob extension. This file contains the re-encoded MPEG-2 video and AC3 audio and is ready for import into DVD authoring software to build a complete disc structure.

Common Use Cases

  • Authoring a DVD from Chinese broadcast or CAVS-encoded video content for playback on standalone DVD players
  • Importing CAVS-sourced news or educational footage into DVD authoring software (like DVD Architect or Encore) that requires pre-encoded VOB-compatible MPEG-2 streams
  • Archiving Chinese satellite broadcast recordings in a widely readable physical media format for institutional libraries
  • Preparing CAVS video content for legacy AV systems in conference rooms or public displays that only accept DVD media
  • Converting CAVS test sequences or reference footage into VOB for quality evaluation on DVD-compliant hardware decoders
  • Creating region-free DVD backups of CAVS-encoded content where AC3 audio is required for surround sound receiver compatibility

Frequently Asked Questions

Yes, this is a lossy-to-lossy transcode — the CAVS video is fully decoded and re-encoded as MPEG-2, which is a less efficient codec than modern AVS/H.264 codecs. At the default quality setting of q:v 4, MPEG-2 output is generally good for standard-definition content, but you will see some generation loss compared to the source. If your CAVS source is high-resolution, note that DVD-Video MPEG-2 is typically constrained to 720x480 (NTSC) or 720x576 (PAL) resolutions.
The VOB/DVD-Video specification mandates specific audio codecs for compatibility with DVD players — AC3 (Dolby Digital) is the most universally supported mandatory audio format for DVD-Video. While VOB can technically carry AAC in some implementations, standalone DVD players and authoring tools overwhelmingly expect AC3. FFmpeg transcodes the CAVS source's AAC audio to AC3 at 192k to ensure broadest hardware compatibility.
Not directly — a valid DVD-Video disc requires IFO and BUP menu/navigation files alongside the VOB, which are generated by DVD authoring software. The VOB produced by this tool contains correctly encoded MPEG-2 video and AC3 audio that meets DVD-Video codec requirements, making it import-ready for authoring tools like DVD Architect, DVDStyler, or Encore. Those tools will then create the full disc structure.
The '-q:v 4' flag controls MPEG-2 output quality on a scale from 1 (best) to 31 (worst). Lowering the value, such as '-q:v 2', will increase quality and file size, while raising it to '-q:v 8' will reduce file size at the cost of more visible compression artifacts. For DVD authoring where disc space is limited, values between 3 and 6 are typical. You can also increase AC3 audio quality by changing '-b:a 192k' to '-b:a 256k' or '-b:a 384k' for more headroom with complex audio.
VOB files have limited metadata support compared to modern containers, and CAVS source metadata rarely maps cleanly to VOB's DVD-Video structure. Most title, author, and descriptive tags from the CAVS source will be dropped during this conversion. Language tags for audio tracks can be set manually in DVD authoring software after importing the VOB. If metadata preservation is critical, document the source tags before converting.
Yes. On Linux or macOS, you can use a shell loop: 'for f in *.cavs; do ffmpeg -i "$f" -c:v mpeg2video -c:a ac3 -q:v 4 -b:a 192k -f vob "${f%.cavs}.vob"; done'. On Windows Command Prompt, use: 'for %f in (*.cavs) do ffmpeg -i "%f" -c:v mpeg2video -c:a ac3 -q:v 4 -b:a 192k -f vob "%~nf.vob"'. Note that because this conversion re-encodes both video and audio, batch processing is CPU-intensive and each file will take proportionally longer than a simple remux.

Technical Notes

CAVS (Chinese Audio Video Standard) was designed as a domestic Chinese alternative to H.264, and files in this format are most commonly encountered in Chinese broadcast, IPTV, and government/institutional media archives. FFmpeg supports CAVS decoding natively, but the codec is not widely supported in downstream tools, making conversion essential for interoperability. The VOB container is a subset of the MPEG Program Stream format and imposes strict codec constraints: video must be MPEG-1 or MPEG-2, and audio must be AC3, LPCM, DTS, or MPEG audio — AAC is not part of the DVD-Video spec and risks incompatibility with hardware players. The '-f vob' flag explicitly forces FFmpeg to write the MPEG Program Stream with VOB-appropriate packet structure rather than a generic MPEG-PS. One important limitation: this tool does not re-scale the video to DVD-standard resolutions (720x480 or 720x576); if your CAVS source is non-standard resolution, you may want to add a '-vf scale=720:480' or '-vf scale=720:576' filter to the FFmpeg command for strict DVD compliance. Multiple audio tracks are supported in the VOB format, but CAVS sources typically carry only a single audio stream, so this is not a practical concern for most conversions from this format.

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