CAVS to AAC Converter

CAVS to AAC Converter

A bare .cavs file is a raw Chinese AVS (AVS1) video bitstream — coded picture data with no container around it and no audio track inside. So if your goal is to pull a soundtrack out of a .cavs and save it as AAC, there is almost nothing to pull: a true raw AVS stream is silent by design, and the output comes out empty. AAC itself is a great target — it is the near-universal MPEG audio format used by iPhones, YouTube, Blu-ray, and most streaming apps — but the audio you want lived in the container the video was demuxed from, not in the bare .cavs. This page is honest about that, explains both formats, and points you to the file that actually holds your sound.

CAVS (AVS1) Format at a Glance

AAC Format at a Glance

Why a Raw CAVS File Has No Sound

AVS1 (GB/T 20090.2) defines a video codec — the picture half of China's first-generation Audio Video Standard. A file saved with a plain .cavs extension is normally a raw elementary stream: a sequence of coded video frames with no container, no audio, and no timing index, which is why FFmpeg reads it through its cavsvideo raw demuxer and why most players refuse to open it at all. An elementary stream carries only one kind of data, so there is no slot inside it for a parallel audio track.

In Chinese AVS broadcast and optical-media workflows the picture was encoded as the AVS stream and the sound was carried as its own separate stream — the two muxed together only when the final container (a transport stream, MP4, or MKV) was built. When that container is demuxed down to a bare .cavs, the audio is left behind. So if you ran this conversion and got a silent or empty AAC, that is not a converter bug — it is the raw AVS stream doing exactly what the format specifies.

Where Your Audio Probably Is

AVS-coded video with sound almost always lived inside a container, and that container is where your soundtrack still is. Point the matching tool at the whole file instead of the demuxed stream:

• A transport stream (.ts): the classic AVS broadcast wrapper — use TS to AAC to decode the audio track an MPEG-TS carries.
• An MP4 container: use MP4 to AAC to pull the audio out of an .mp4.
• A Matroska (.mkv) container: use MKV to AAC — MKV commonly pairs video with AAC, AC-3, or other audio.

If you only want the video in a playable package rather than its audio, you are on the wrong tool — CAVS to MP4 wraps the raw stream into a file ordinary players and devices can open.

How to Convert CAVS to AAC

1. Upload Your CAVS File: Drag and drop your .cavs onto the page or click "+ Add Files" to browse from your computer. You can queue several files to process with the same settings.
2. Pick a Quality Preset: Open Advanced Options and choose a Quality Preset (Highest down to lower presets) for a one-click AAC bitrate, or switch to Custom Bitrate and pick Constant Bitrate for predictable size or Variable Bitrate for better quality at the same average. Specific file size lets you target an exact size in MB.
3. Set Audio Channel, Sample Rate, or Trim (Optional): Audio Channel and Audio Sample Rate both default to Original, which copies the decoded audio untouched; switch Channel to Mono to roughly halve a voice file, or use Trim to export only part of the timeline.
4. Convert and Download: Click "Convert" and download your AAC. No sign-up, no watermark.

Frequently Asked Questions

Why is my CAVS to AAC output silent or empty?

Because a raw .cavs file is an AVS1 video elementary stream and holds no audio. AVS1 (GB/T 20090.2) defines only a video codec, so there is no soundtrack inside a bare .cavs to decode, and any AAC produced from it will be silent or empty. The audio for that footage lived in the container — a transport stream, .mp4, or .mkv — that the video was demuxed from. Convert that container to AAC instead; for the broadcast .ts case start with TS to AAC.

What is a .cavs file, and is there such a thing as "CAVS audio"?

A .cavs is a raw Chinese AVS video bitstream — the picture half of AVS1, China's first-generation Audio Video Standard, standardized as GB/T 20090.2 and adopted as a national standard in February 2006 by the AVS Workgroup (founded June 2002). There is no "CAVS audio": the .cavs extension is a video-only elementary stream. When content is described as "AVS," the sound riding alongside it is a separate stream in the container, not part of the .cavs itself. So this page disambiguates rather than promising audio a raw stream never had.

Is .cavs the same as a .avs AviSynth script?

No, and they are easy to confuse. A .cavs file is a raw AVS1 video bitstream — actual coded picture data from the Chinese AVS standard. A .avs file is an AviSynth script: a small text file of frameserving instructions, not media at all. Neither one contains an audio track you can extract to AAC. If you uploaded an AviSynth script by mistake, there is no AVS picture or sound inside it.

Why pick AAC, and should the file be .aac or .m4a?

AAC (Advanced Audio Coding) was standardized as MPEG-2 Part 7 (ISO/IEC 13818-7) in 1997 and extended in MPEG-4 Part 3 as the intended successor to MP3, and it generally sounds better than MP3 at the same bitrate. It plays natively almost everywhere — iOS, Android, YouTube, Blu-ray, and HDTV. This tool outputs a raw .aac (ADTS) stream that players read directly; the same audio is also commonly delivered as .m4a, which is AAC wrapped in MP4 so it can carry title, artist, and album-art tags. Add those in a tag editor afterward if you need them.

If I convert the right container, will the AAC lose quality?

Some, but usually not in a way you will hear. The audio inside an AVS container (often AC-3, MP2, or AAC) is already lossy, so re-encoding to AAC is a second lossy pass and sheds a little detail. Choosing a Quality Preset around 192 kbps or higher keeps the result transparent for casual listening, and there is no benefit to encoding above the source bitrate since you cannot recover quality the original never had. In our testing, a true raw .cavs elementary stream has no audio track to work with, so regardless of bitrate the output is silent — only a real container produces a normal AAC file at the selected quality.

How are my files handled, and are they kept private?

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