CAVS to FLAC Converter

Convert CAVS to FLAC: Read This First

A bare .cavs file is a raw Chinese AVS (AVS1) video bitstream — by design it carries picture only, with no audio track inside it. So if your goal is to pull a soundtrack out of a .cavs and save it as lossless FLAC, there is usually nothing to pull: the resulting file would be silent. This page is honest about why, shows how the converter behaves, and points you to the file that actually holds your audio.

Why a Raw CAVS File Has No Sound

CAVS is the video half of China's first-generation Audio Video Standard (AVS1), standardized as GB/T 20090.2 and adopted as a national standard in February 2006 by the AVS Workgroup, which was founded in June 2002. The .cavs extension specifically names the AVS1-P2 (JiZhun profile) video bitstream — in FFmpeg it is handled by the cavsvideo raw video demuxer, which registers a single video stream and nothing else. A file saved with a plain .cavs extension is an elementary stream: a sequence of coded AVS video frames, with no container around it to hold a parallel audio track, so there is no sound to decode.

In Chinese broadcast and optical-media workflows the picture is encoded as the AVS stream and the audio is carried separately, only joined ("muxed") later into a combined container such as an MP4, MKV, or transport stream. So a true .cavs on its own is mute. If you ran this conversion and got a silent FLAC, that is not a bug in the converter — it is the raw AVS stream doing exactly what the format specifies.

Note: .cavs here means a raw AVS1 video elementary stream. Do not confuse it with .avs AviSynth script files, which are a different thing entirely. This page is about the video bitstream.

How to Convert CAVS to FLAC

1. Upload Your CAVS File: Drag and drop your .cavs onto the page, or click "+ Add Files" to choose it from your computer. You can queue several files to process with the same settings.
2. Set the Compression Level: Open "Show All Options" and use the Compression level slider. FLAC is lossless at every setting — the level only trades encode speed against file size. A lower number encodes faster but leaves the file larger; a higher number squeezes the smallest file. The audio itself is bit-for-bit identical either way.
3. Set Audio Channel and Sample Rate (Optional): Audio Channel and Audio Sample Rate both default to Original, which copies the decoded audio untouched — the safest choice. Force a fixed rate such as 44100 Hz or 48000 Hz only if a target device needs it, and use Trim to grab just a portion of the timeline.
4. Convert and Download: Click "Convert" and download your FLAC. No sign-up, no watermark.

Walk-through: Will Your CAVS File Actually Have Sound?

Whether you get audio depends entirely on what you actually uploaded, because the AVS1 video specification defines only picture — any audio was carried alongside it as its own stream. The common cases:

• A true raw .cavs elementary stream: This is video only. A FLAC made from it will be empty or silent — there is nothing inside to extract. Nothing in the settings can create a soundtrack that was never in the file.
• A container that was misnamed .cavs: Occasionally a muxed file (an MP4, MKV, or transport stream from a Chinese set-top box or karaoke export) gets saved with a .cavs extension. If your file is secretly a container with a real audio track, the converter will decode that track to FLAC normally. But that is the exception, not the rule, and the AVS decoder may simply reject a file that is not a raw stream.
• You actually want the soundtrack of an AVS video: then you are starting from the wrong file. Upload the full container — the MP4, MKV, or transport stream that holds both the AVS video and the audio — to the matching tool below.

If you are not sure whether your file is a bare stream or a container, check the extension and how it plays: a raw .cavs cannot be opened by ordinary media players at all, while .mp4, .mkv, and .ts can carry both video and audio together and play in normal software.

Where Your Audio Probably Is

• The original playable file: if you ever watched this footage with sound, that source was almost certainly a container — an MP4, MKV, or transport stream — not the bare .cavs. Convert that file, not the demuxed stream.
• An MP4 container: use MP4 to FLAC to decode the audio track from an MP4 (which can wrap AVS video alongside an audio track) into lossless FLAC.
• An MKV or transport stream: use MKV to FLAC for Matroska files, or TS to FLAC for the MPEG transport streams common in Chinese broadcast capture, both of which interleave video and audio.

When This Doesn't Work

If your CAVS file is a true elementary stream with no companion audio, no tool can manufacture sound that was never encoded — the fix is to find the original container or the separate audio file. And keep one thing in mind even when audio is present: broadcast and set-top audio is almost always a lossy codec such as AAC, MP2, or AC-3, so packaging it into FLAC gives you a lossless wrapper around already-lossy audio. FLAC will preserve exactly what is there, but it cannot restore detail the original lossy encode discarded — it is not a quality upgrade. If you only want the video in a playable package rather than its audio, transcode the raw stream with CAVS to MP4 to make it open in normal players, or use CAVS to WebM for a web-friendly container.

Frequently Asked Questions

Why is my CAVS to FLAC output silent or empty?

Because a raw .cavs file is an AVS1 video elementary stream and holds no audio. There is no soundtrack inside the file to decode, so any FLAC produced from a bare .cavs will be silent. The audio for that footage lived in the container — an MP4, MKV, or transport stream — that the video was demuxed from. Convert that container to FLAC instead.

Does a .cavs file contain audio I can extract?

Normally no. CAVS, standardized in China as GB/T 20090.2 (AVS1), is a video-only standard, and a plain .cavs is a raw AVS video bitstream handled by FFmpeg's cavsvideo raw demuxer with no audio track. You only get sound out if the file you uploaded is actually a container (such as an MP4 misnamed .cavs) that happens to carry an audio track alongside the video.

Will FLAC improve the quality of audio extracted from an AVS video?

No. FLAC is the Free Lossless Audio Codec from the Xiph.Org Foundation — standardized in December 2024 as IETF RFC 9639 — so it stores whatever it is given without further loss. But the audio paired with AVS broadcast video was almost always encoded with a lossy codec like AAC, MP2, or AC-3. Converting that to FLAC produces a lossless file that faithfully preserves the lossy source; it cannot recover detail the original encode already threw away. FLAC here means a clean, edit-ready copy, not a higher-fidelity one.

How do I get FLAC audio from an AVS source that actually has sound?

Start from a file that genuinely contains an audio track. If you have an MP4, use MP4 to FLAC; for a Matroska file use MKV to FLAC; for an MPEG transport stream use TS to FLAC. All three interleave video and audio, so the converter has a real audio track to decode into FLAC. A bare .cavs stream does not.

What does the Compression level slider do for FLAC?

FLAC is lossless at every compression level, so the slider only changes how hard the encoder works to shrink the file — not the audio quality. In our testing, a higher level produces a smaller FLAC and a slower encode, while a lower number finishes faster but leaves a slightly larger file. The decoded samples are bit-for-bit identical regardless of where you set it.

Is this CAVS converter free, and how is my file handled?

Yes. There is no sign-up and no watermark. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically a few hours after conversion — never shared or made public.