CAVS to XviD Converter

CAVS to Xvid: The File You Get Is an AVI, and You Should Rename It

Xvid is not a container. It is an encoder — a well-known open-source implementation of MPEG-4 Part 2 Advanced Simple Profile — and files encoded with it have always lived inside AVI. There is no such thing as an "Xvid file format", which puts this page in an awkward position: you asked for .xvid, so that is the extension you get, but what is inside it is a RIFF/AVI container.

This is checkable at the byte level. A file written with this page's settings begins with the ASCII sequence RIFF, four length bytes, then AVI LIST, and any media analyser identifies the container as AVI and the video stream as MPEG-4 Part 2 carrying the FourCC xvid. Copy the same bytes to a file named .avi and it opens immediately in players that would not touch the .xvid version. So: convert here if a workflow demands the .xvid extension, then rename to .avi the moment you want to play it — or skip the detour and use CAVS to AVI, which produces the same class of file under a name every player recognises.

How to Convert CAVS to Xvid

1. Upload Your CAVS File: Drag the .cavs onto the page or click "+ Add Files". A .cavs is a bare AVS1 video bitstream — coded frames with no container, no audio and no seek index — which is why most players refuse to open one directly. Several can be queued and all convert with the same settings.
2. Leave Video Codec Alone: The list has exactly one entry, Xvid, and it is already selected. That is the whole point of this target, and there is nothing to decide. The Audio Codec list nominates MP3 but has nothing to work with, because the source carries no sound.
3. Set Constant Quality and Video resolution: File Compression opens on Quality Preset at "Very High (Recommended)", but Constant Quality is the control worth using here — on Xvid it is a quantiser on a 1-31 scale opening at 5, where lower means better quality and a larger file. Video resolution opens on Keep original; Trim takes a Start time and a Duration.
4. Convert and Download: Click Convert, save the .xvid, and rename it to .avi if you want it to play. Files are uploaded over an encrypted connection, decoded and re-encoded on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared or made public.

What the .xvid File Actually Is

The rename is safe precisely because nothing about the file changes — the extension is metadata that lives in the filename, not in the bytes, and both names describe the same RIFF container. What the rename fixes is the guessing that players and file managers do: handed .xvid, many refuse to try at all rather than sniffing the header.

The One Control That Moves the Output

Because Xvid is a quantiser-based encoder rather than a CRF one, the Constant Quality field is a 1-31 scale, and it works. Measured on a 704x576 six-second clip:

A word of warning about the label: the field is titled CRF, which is the H.264 convention, but on Xvid the number is a quantiser and the two scales are not interchangeable. A value of 23 would be a reasonable H.264 CRF and is close to the worst end of the Xvid quantiser range. If you have been carrying a number over from another conversion, discard it and use the 1-31 table above instead.

The other modes render too — Specific file size, Constant Bitrate, Variable Bitrate and Constraint Quality — and all of them work on Xvid. Quality Preset, the mode the page opens on, scales the source clip's bitrate rather than setting an absolute one, which on a raw AVS stream with no reliable container metadata is a less predictable starting point than simply naming a quantiser.

Frequently Asked Questions

Why does my .xvid file not open in VLC or Windows Media Player?

Because of the extension, not the contents. The file is a RIFF/AVI container holding MPEG-4 Part 2 video, which both of those players handle perfectly well — but .xvid is not an extension either of them is registered for, so they either refuse outright or hand it to the wrong handler. Rename the file to .avi and it will open. Nothing inside the file needs to change, because there is no .xvid container format for it to be converted out of.

Is Xvid the same as DivX?

They are two implementations of the same underlying standard, MPEG-4 Part 2 Advanced Simple Profile, and files from either will generally play on a decoder built for the other. Xvid is the open-source implementation, written as a free alternative after the original DivX codec became a commercial product. In practice the choice matters only when a specific device or piece of software names one of them explicitly — some DVD players of the mid-2000s were certified for one and not the other. If you need the DivX spelling instead, the site has a matching target for it.

Why is the converted file silent?

Because a raw .cavs has no audio in it. It is a video elementary stream: coded picture data with no container, no sound and no timing index. In Chinese AVS broadcast and optical-media workflows the picture was encoded as one stream and the sound as another, and the two were multiplexed together only when the final container was built, so the bare .cavs you have is the picture half on its own. The Audio Codec dropdown still renders and still nominates MP3, but there is nothing for it to encode. If the soundtrack is what you were after, you need the original container, not the demuxed stream.

Is this a rewrap of my existing frames, or a re-encode?

A re-encode. AVI does not carry AVS1 in any form, so the decoder reconstructs the pictures from the AVS1 bitstream and Xvid compresses them again as MPEG-4 Part 2 — one lossy generation, with no setting that avoids it. That is also why the conversion takes real time rather than finishing instantly, and why the Constant Quality value matters: it decides how much of the original survives the second pass. Set it to 2 or 3 if the .cavs is your only copy of the material.

What is a .cavs file, exactly?

A raw Chinese AVS video bitstream — specifically the AVS1-P2 Jizhun profile, the first generation of the Audio Video Standard adopted as Chinese national standard GB/T 20090.2 in 2006 by the AVS Workgroup, which was established in June 2002. It is an elementary stream: coded frames with no container around them, no audio, no duration field and no seek index. That is why ordinary players will not open one and why wrapping it into something — AVI, MP4, MKV — is the first step in making it usable. It is unrelated to .avs AviSynth scripts, despite the similar name.

Will the output keep the original frame size and frame rate?

The frame size, yes — Video resolution opens on Keep original, so the picture is encoded at whatever size the AVS stream decoded to, typically a standard-definition broadcast size. The frame rate is less certain, because a bare elementary stream declares none: the decoder infers timing from the bitstream, and if the result reports an unexpected duration or rate, that is the missing container metadata showing through rather than a fault. If exact timing matters, convert the original container the stream came from rather than the demuxed .cavs.

Can I put Xvid video into MP4 or MKV instead of AVI?

Technically yes — MPEG-4 Part 2 is legal in both — but it is rarely what you want. The reason to choose Xvid at all is compatibility with hardware and software from the AVI era, and putting the codec in a modern container throws that away while keeping the codec's much weaker compression. If you want a modern container, take the modern codec too: CAVS to MP4 gives you H.264 in MP4, which is smaller at the same quality and plays on essentially everything.

How large should I expect the file to be?

Predictably, once you have set Constant Quality, because the quantiser controls the rate directly. Our 704x576 six-second test clip produced 2,999,660 bytes at quantiser 2, 1,732,642 bytes at 5, 842,302 bytes at 12 and 277,840 bytes at 31 — roughly 500 KB, 290 KB, 140 KB and 46 KB per second of standard-definition video. Scale from there for your own material, remembering that busier footage costs more at every setting. If you need to hit an exact number instead, Specific file size derives a bitrate from your target and the clip duration.

How are my files handled while this is running?

Uploads travel over an encrypted connection, are decoded and re-encoded on our servers, and both the upload and the output are deleted automatically after a few hours. Files are never shared or made public, no account is required and no watermark is added. There is no fixed per-file cap — upload size and connection speed are the practical limit — and raw elementary streams tend to be modest because they carry neither audio nor container overhead.