CAVS to FLV Converter

Convert CAVS to FLV: What This Tutorial Covers

This walk-through is for anyone holding a raw .cavs file — a Chinese AVS (AVS1) video bitstream that almost nothing plays directly — who needs it inside an FLV because a legacy player, CMS, e-learning package or media server still ingests that extension. Two cautions before you start: a bare .cavs is video-only, so the FLV comes out silent, and FLV is no longer a web-delivery format. If the goal is simply a file that plays everywhere, CAVS to MP4 is the better target; convert to FLV when something downstream genuinely demands it.

How to Convert CAVS to FLV

1. Upload Your CAVS File: Drag the .cavs onto the page or click "+ Add Files" to browse. Several raw AVS streams can be queued and converted with the same settings in one pass.
2. Pick a Video Codec: Open Advanced Options and choose from Video Codec — "FLV" (Sorenson Spark) for maximum legacy compatibility, "H.264" for a much sharper picture at the same bitrate, or the two "Flash Video" screen-capture codecs for slide and screencast material.
3. Set File Compression, Resolution or Trim: Under File Compression the Preset dropdown is preselected to "Very High (Recommended)"; "Specific file size" targets an exact size in MB instead. Video resolution offers "Keep original", presets, a percentage or an exact "Width x Height", and Trim switches from "Unchanged" to a "Time Range" with a start time and duration.
4. Convert and Download: Click "Convert" and take the FLV. No sign-up, no watermark.

Walk-through: Choosing the Codec Inside the FLV

FLV is a container, and the codec you put inside it decides both how the file looks and which of the compression controls stay on screen. The four choices are not interchangeable — two of them are screen-recording codecs that were never meant for camera or broadcast footage.

For a .cavs broadcast capture, only the first two are sensible. Take "FLV" if the receiving system is genuinely ancient, and "H.264" whenever it will accept it — the picture is noticeably cleaner at the same file size, which matters because the AVS source has already been through one lossy pass. Note that switching to Sorenson Spark removes the Variable Bitrate mode from the File Compression list; Constant Bitrate, Constant Quality, Constraint Quality, Specific file size and the quality presets all remain.

What Crosses Over From the Source

Common Errors and How to Fix Them

• "The FLV has no sound" — Expected. A raw .cavs is an AVS1 video elementary stream with no audio to carry, so the output is mute. The audio codec list (AAC, MP3, ADPCM_SWF) only comes into play for sources that arrive with a soundtrack.
• "My player won't open the .cavs so I can check it first" — Most mainstream players ship no AVS1 decoder. The open-source cavs decoder covers the AVS1-P2 Jizhun profile, which is what makes a server-side conversion the practical route; once it is FLV, far more tools can read it.
• "No browser will play the finished FLV" — Correct and unavoidable. Adobe ended Flash Player support on 31 December 2020 and began blocking Flash content on 12 January 2021, so nothing plays .flv in a browser now. Verify the file in VLC or mpv, and convert to MP4 for anything web-facing.
• "The picture looks soft or blocky" — Second-generation lossy loss. Move Video Codec to H.264, keep the Preset at "Very High" or "Highest", and leave the resolution alone so the encoder starts from the full frame.
• "The output is enormous for a short clip" — You probably selected one of the Flash Screen Video codecs, which are tuned for flat screen recordings and cope badly with camera noise and film grain. Switch back to FLV or H.264.
• "A long broadcast capture stalls on upload" — The limit is upload size and time. Use Trim → Time Range to send only the segment you actually need.

When This Doesn't Work

This conversion cannot manufacture quality or sound the source never had. The .cavs is already lossily coded, FLV cannot carry AVS1, so every frame is decoded and re-encoded from scratch — standard-definition footage stays standard-definition. It also cannot add an audio track that was never in the elementary stream. And if you actually uploaded a .avs AviSynth script — a small text frameserving file that shares an extension with raw AVS streams in some tools — there is no coded picture inside it to convert. When you want footage that simply plays, use CAVS to MP4 or start from the CAVS Converter hub and pick a modern target.

Frequently Asked Questions

What exactly is a .cavs file?

A raw video elementary stream coded with AVS1, China's first-generation Audio Video coding Standard, published as national standard GB/T 20090.2-2006 in February 2006 by the AVS Working Group, which began work in June 2002. The picture uses the AVS1-P2 "Jizhun" (base) profile. These files come out of Chinese digital-TV, IPTV and set-top-box pipelines and are rare elsewhere, which is why general-purpose players usually cannot open them.

Is FLV dead now that Flash Player is gone?

The delivery workflow is dead; the file format still reads. Adobe ended Flash Player support on 31 December 2020 and started blocking Flash content on 12 January 2021, so no browser plays .flv natively and no modern site serves it. The container itself still opens in VLC, mpv and ffmpeg-based tools, because those decoders never relied on the plug-in. Convert to FLV only when a specific legacy system asks for it.

Why does the converted FLV have no sound?

Because the source has none. In AVS broadcast workflows the audio was coded as a separate stream and muxed in only when the transport container was built, so a demuxed .cavs is picture-only and the FLV inherits that silence. If you still have the original container that held both streams — an MP4, MKV or transport stream — convert that file instead and the audio comes along.

Which codec should I choose if I do not know what will play the file?

H.264. It is the sharpest of the four at any given bitrate, every desktop player made in the last fifteen years decodes it, and it keeps all seven File Compression modes available. Only fall back to "FLV" (Sorenson Spark) if the target system predates Flash Player 9 Update 3, since that is the release that introduced H.264-in-FLV.

Why did the File Compression section vanish when I changed the codec?

Because you selected "Flash Video" or "Flash Video (v2)". Those are the Flash Screen Video codecs, designed for screen recordings, and they do not expose bitrate or quality-preset control — so the tool hides the File Compression group instead of showing settings that would be ignored. Switch back to FLV or H.264 and the controls return.

Will converting CAVS to FLV improve or lose quality?

It loses a little, in one direction only. The stream is already lossily coded with AVS1, FLV cannot carry AVS1, so the frames are decoded and re-encoded into a different codec. That second pass discards data and no setting brings it back. Keep the Preset high and the resolution native and you avoid throwing away more, but there is no path to adding detail in.

Can I trim a long capture instead of converting the whole thing?

Yes, and on a broadcast capture it is usually the right move. Set Trim to "Time Range", then enter a start time and a duration in either seconds or HH:MM:SS.sss. Only the selected span is encoded, which cuts both the output size and the conversion time.

How are my files handled, and how long do you keep them?

Your file is uploaded over an encrypted connection, decoded and re-encoded into FLV on our servers, and deleted automatically a few hours later — no sign-up, no watermark, never shared or made public.