CAVS to SWF Converter

CAVS to SWF: Wrapping an AVS1 Stream in Flash

This converter takes a Chinese AVS1 elementary stream (.cavs) and re-encodes it into a Shockwave Flash movie. It is a genuinely legacy destination — Adobe stopped supporting Flash Player on 31 December 2020 and blocked Flash content from running on 12 January 2021 — so the honest reasons to do this are narrow: feeding an old authoring tool, an industrial HMI panel, a courseware package or a projector build that only ingests .swf. If you simply want the clip to play, CAVS to MP4 is the target you actually want.

How to Convert CAVS to SWF

1. Upload Your CAVS File: Drag the .cavs onto the page or click "+ Add Files". Several files can be queued and each is decoded on our servers, so no AVS1 codec has to be installed on your machine.
2. Confirm the Video Codec and Audio Codec: Video Codec offers exactly two entries, FLV and MJPEG, and opens on FLV. Audio Codec offers only MP3 — the SWF wrapper on this page has no other audio choice.
3. Set File Compression, Video resolution and Trim: File Compression opens on Quality Preset at Very High (Recommended); the other modes here are Specific file size, Constant Bitrate, Constant Quality and Constraint Quality. Video resolution opens on Keep original, and Trim starts on Unchanged with a Time Range mode for exporting one section.
4. Convert and Download: Click Convert and save the .swf. Files upload over an encrypted connection, are processed on our servers, and are deleted automatically after a few hours — no sign-up, no watermark, never shared or made public.

FLV or MJPEG: the Two Payloads on This Page

Our SWF output is written as an uncompressed SWF version 6 file — the Flash Player 6 generation, which is the release that introduced video playback in the first place. That is deliberate: a video-bearing SWF has no reason to declare a later version, and older authoring tools and players accept version 6 readily.

What the Quality Preset Does When the Source Has No Bitrate

FLV is not a CRF codec, so Quality Preset cannot hand it a quality number the way it would for H.264. Instead the preset multiplies the source video's bitrate and targets the result. That works well on a normal file — but a .cavs is a bare elementary stream with no container around it, so it reports no bitrate and no duration at all. When that happens, our probe substitutes a fixed 2.56 Mbps baseline and the preset scales that instead:

The practical consequence is that on a raw stream the preset ladder is a fixed bitrate ladder, not a "percentage of what you had". A standard-definition broadcast capture that really ran at 1.5 Mbps will come out larger than it went in at the default preset. If you know roughly what bitrate you want, Constant Bitrate gives you it directly and is the better control here. If you have a hard byte ceiling, use Specific file size.

Sound, Sample Rate, and Why 44.1 kHz Is Not Negotiable

Two things decide what the audio track ends up as. The first is the source: a .cavs file is a video elementary stream, so in the overwhelming majority of cases there is no audio in it at all, and the SWF comes back silent. Nothing is added to fill the gap — a video-only input produces a video-only SWF rather than one with a track of silence.

The second is the container. SWF only accepts a handful of audio sample rates, so our pipeline forces 44,100 Hz on every SWF conversion regardless of what the source ran at. There is no control for this on the page and no way to opt out of it, which is correct behaviour: a rate the container cannot describe would produce a file that plays at the wrong speed or not at all.

Frequently Asked Questions

Will the SWF actually play anywhere now that Flash is dead?

Not in a browser. Adobe stopped supporting Flash Player on 31 December 2020 and began blocking Flash content in the player on 12 January 2021, and every mainstream browser removed its Flash plugin around the same time. What still opens .swf files is standalone software: old Flash projectors, some authoring and courseware tools, industrial panels that were built around it, and the Ruffle emulator — which ships a Flash Video decoder, though embedded-video playback is worth testing on your specific file rather than assuming. Convert to MP4 if you need something that just plays.

Why is my SWF silent?

Almost certainly because the source had no sound to carry. A .cavs file holds a bare AVS1 video elementary stream — there is no container in it to hold an audio track alongside the video, so the great majority of these files are video-only. If the audio you care about lives in a separate file, you will need to combine them before converting rather than expecting this page to find it.

Can I keep the original sample rate?

No. SWF supports only a small set of sample rates, and our pipeline forces 44,100 Hz on every SWF output rather than letting an unsupported rate through. That is why there is no sample-rate control on this page. The re-sample is a normal audio conversion — it does not damage the recording in any way you will hear, and it is what keeps the file playing at the right speed.

Should I choose FLV or MJPEG?

FLV, in almost every case. It is the codec Flash video was built around, it compresses across frames so files stay a sensible size, and it is what a player expects to find inside an SWF. MJPEG stores every frame as a separate JPEG, which makes each frame independently decodable but inflates the file dramatically for the same visual quality. Choose MJPEG only if some downstream tool specifically requires per-frame JPEG data.

Why did my file get bigger than the CAVS I uploaded?

Because the quality preset had nothing to scale from. A raw .cavs reports no bitrate, so instead of taking a percentage of your file's own rate, the preset works from a fixed 2.56 Mbps baseline — and the default Very High preset targets 1.32 times that, roughly 3.38 Mbps. If your capture was a 1.5 Mbps standard-definition broadcast, that is more than twice what it started with. Switch File Compression to Constant Bitrate and name the rate you actually want.

What is a .cavs file in the first place?

It is the video half of AVS1, China's own audio-video coding standard, published as the national standard GB/T 20090.2-2006 by the AVS Workgroup that was set up in June 2002. It was designed as a domestic alternative to MPEG-2 and H.264 for Chinese digital television, IPTV and set-top boxes, and decoders shipped inside that hardware rather than in browsers or desktop operating systems — which is why a .cavs file usually will not open on a normal computer.

Can I convert only part of the clip?

Yes. Open Trim, switch it from Unchanged to the Time Range mode, and give a Start time and a Duration. Only that section is decoded and encoded, which also keeps the SWF small. If you would rather cut first and convert afterwards, Video Cutter accepts .cavs directly.

Does converting to SWF lose quality?

Yes, unavoidably, and twice over. Your AVS1 source is already lossy, and the server always re-encodes rather than copying the existing video stream across — there is no way to move AVS1 data into an SWF untouched, because SWF cannot carry it. So the output is a fresh FLV or MJPEG encode of an already-compressed picture. Keeping the resolution on Keep original and the preset high is the way to minimise the second generation of loss.

What happens to my file after the conversion?

It is uploaded over an encrypted connection, decoded and re-encoded on our servers, and both the upload and the finished .swf are deleted automatically after a few hours. Files are never shared or made public, there is no sign-up and no watermark, and your original .cavs is left untouched — the SWF is written as a new file.