CAVS to OPUS Converter

CAVS to Opus: Why Your Output Is Silent (and How to Get Real Audio)

A bare .cavs file is a raw Chinese AVS (AVS1) video elementary stream — coded picture data only, with no audio track and no container wrapped around it. So if your goal is to pull a soundtrack out of a .cavs and save it as Opus, there is normally nothing to pull: the conversion runs, but the Opus comes out silent or empty. That silence is not a converter bug — it is the format telling you the truth about what it holds. The target is right: Opus is the modern, open, royalty-free choice for audio. It just cannot conjure sound that the .cavs never carried. This tutorial explains where the audio actually lives and routes you to the conversion that produces a real Opus track.

How to Convert CAVS to Opus

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 run with the same settings.
2. Pick a Quality Preset or Bitrate: Open "Show All Options" and leave Quality Preset on its default (Highest), or switch File Compression to Custom Bitrate, Constant Bitrate, or Variable Bitrate to set the Opus rate yourself. The output codec is fixed to Opus.
3. Set Audio Channel, Sample Rate, or Trim (Optional): Audio Channel and Audio Sample Rate both default to Original; switch Channel to Mono for a voice-only file, or use Trim to export just part of the timeline. None of these recovers audio a video-only .cavs never had.
4. Convert and Download: Click "Convert" and download your .opus file. No sign-up, no watermark.

Walk-through: Right Codec, Wrong Source

Opus is genuinely the right destination for this kind of job, so it is worth knowing what it does well before you point it at the correct file. Opus is standardized by the IETF as RFC 6716, published September 2012, and it is, in the project's own words, "totally open, royalty-free." It fuses two layers — SILK for speech and CELT for music — and spans roughly 6 kbit/s to 510 kbit/s, which is why it stays efficient across very different material. The catch on this page is purely the source: a .cavs is the video half of a recording, so feed Opus the file that still has the sound and set the rate to match the content:

• Voice, talk, or low-fidelity broadcast audio — leave Quality Preset high, or pick a low Variable Bitrate band; Opus holds up well at low rates.
• Music or full-range audio — choose a higher Quality Preset, or set Custom Bitrate to 128-192 kbps for near-transparent results.
• A long recording you only need part of — use Trim to export a single segment instead of the whole timeline.
• A small file for chat or web — Opus is what WhatsApp, Discord, and YouTube already use, so a 48-96 kbps export plays back natively in modern apps and browsers.

The point is unchanged: every one of these settings assumes there is an audio stream to encode. A bare .cavs has none, so the controls change nothing about the silence — they only matter once you switch to a source that actually carries audio.

Common Errors and How to Fix Them

• "My Opus file is silent" — Expected when the input is a true raw .cavs. AVS1 defines video coding only, so there is no audio elementary stream inside the file to encode. Convert the container the video came from instead — TS to Opus or MP4 to Opus.
• "My player shows zero length or won't open the .cavs" — A bare elementary stream has no index or container header, so most players refuse it directly; tools built on FFmpeg read it through a dedicated raw AVS demuxer. This is normal for a stripped stream, not corruption.
• "I wanted the video, not the audio" — Opus is audio-only and discards the picture. To keep the moving footage in a broadly playable file, wrap the stream with CAVS to MP4 instead.
• "The file is binary garbage in a text editor" — Good: that means it is genuine coded AVS video, not an AviSynth .avs script. If it does open as readable text, see the FAQ below — it is a different kind of file entirely.

When This Doesn't Work

If the original recording genuinely never had sound, no tool and no Opus setting can create one — the data simply is not in any file. The honest fix is to find the source that still contains audio. Chinese AVS broadcast and optical-media content is almost always muxed into an MPEG transport stream (.ts) or an .mp4 that wraps the AVS video next to a separate audio track; when that container was demuxed down to a bare .cavs, the audio was left behind in the original. Go back to that .ts or .mp4 and convert it, and the audio track is read and encoded normally. If all you ever received was the video half of a project, there is no soundtrack to recover.

Frequently Asked Questions

Why is my CAVS to Opus output silent or empty?

Because a bare .cavs is a Chinese AVS (AVS1) video elementary stream and holds no audio. AVS1 defines video coding only — the video coding part was promulgated as the national standard GB/T 20090.2 in February 2006, with efficiency competitive with the H.264 of its era — so there is no soundtrack packed inside a raw .cavs for the converter to encode, and any Opus produced from it is silent. The audio for that footage lived in the container the video was demuxed from, usually an MPEG transport stream (.ts) or an .mp4. To get real sound, convert that container instead: TS to Opus or MP4 to Opus.

My AVS recording definitely had sound — where is it now?

It is still in the original container, not in the .cavs. Chinese AVS broadcast and optical-media content is muxed: the AVS video and a separate audio track are packed together inside an MPEG transport stream or MP4. When a tool demuxes that file down to a bare .cavs, it keeps only the video elementary stream and leaves the audio behind in the source. Point the converter at the original .ts or .mp4 (TS to Opus, MP4 to Opus) and the audio track is read and encoded normally.

Is Opus the right target here, or should I use MP3?

For a new export, Opus is one of the strongest targets available — it is open, royalty-free, standardized by the IETF as RFC 6716 in September 2012, and efficient from low-bitrate voice up to full-quality music. The one caveat on this page is the source, not the codec: Opus is the right destination, but a video-only .cavs is the wrong file to feed it. The only reason to prefer MP3 is maximum compatibility with old hardware; if that is your concern, CAVS to MP3 follows the same logic and carries the same video-only caveat — both stay silent unless the source actually holds audio.

Could my file actually be an AviSynth .avs script instead?

Worth checking, because the extensions look similar. An .avs AviSynth file is a small text script that tells a video frameserver how to process other clips — it is not video data and not Chinese AVS, and it holds no audio or video to convert at all. A .cavs (Chinese AVS) file is genuine coded video. If your file opens as readable text in an editor, it is an AviSynth script. If it is binary coded data from Chinese digital TV or broadcast, it is a real AVS1 video stream — still video-only, so the silent-output explanation above applies.

I actually wanted the video, not the audio — what should I use?

Then Opus is the wrong target, because Opus is an audio-only format and discards the picture. To keep the moving footage in a broadly playable file, transcode the stream with CAVS to MP4 instead, which wraps the AVS video into an MP4 that today's players and devices open directly. The first-generation AVS standard was developed by China's AVS Workgroup, founded in June 2002, and its video coding remains the picture half of these recordings — so wrapping it as MP4 is how you get something that plays everywhere.

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

Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically a few hours after conversion — never shared or made public. There is no sign-up and no watermark. In our testing, a genuine raw .cavs video stream yields a silent Opus file regardless of the bitrate selected, while feeding a real .ts or .mp4 container that holds an audio track produces a normal Opus file at the chosen quality.