CAVS to VMS Converter

Get VMS audio from CAVS videos in your browser for free

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Clean Audio Output

The VMS audio extracted from your CAVS video preserves the original sound quality. Adjust bitrate for the best possible result.

Any Device Works

Desktop, laptop, tablet, or smartphone — the converter adapts to your screen and works in any modern web browser.

No Account Required

Start converting immediately — no registration needed for basic use. Create an account only if you want extended features.

How to convert CAVS to VMS

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose vms or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your vms file right afterwards

About formats

CAVS (Chinese Audio Video Standard) is a video compression standard developed by the Audio Video Coding Standard Workgroup of China and adopted as a national standard (GB/T 20090.2) in February 2006. The project began in 2002 with the aim of creating an independent compression technology that could serve the massive broadcasting and multimedia infrastructure in China without relying on foreign-licensed codecs. CAVS, also referred to as AVS1, achieves compression efficiency comparable to H.264/AVC while utilizing a simpler patent framework with significantly lower licensing costs. The standard supports video resolutions from standard definition up to high definition, making it suitable for both terrestrial digital television broadcasting and broadband streaming. Key technical features include 8x8 block transforms, multiple prediction modes, and a loop filter designed to reduce blocking artifacts at low bit rates. The Chinese government endorsed CAVS as the mandatory compression standard for the national digital TV broadcasting system, ensuring broad deployment across set-top boxes and television receivers in the country. While CAVS has limited international adoption compared to H.264 or HEVC, its significance lies in serving one of the largest media markets in the world and demonstrating a viable national alternative to globally dominant video coding standards.
Initial release: February 2006
VMS (Voice Messaging System) is a compressed audio format designed for telephony and voice mail applications, originally used in Germany. Files with the .vms extension encode spoken audio using Continuously Variable Slope Delta modulation (CVSD), a method suited to low-bandwidth voice transmission over telephone networks. The format operates at 8 kHz, matching the standard digital telephony sampling frequency, and produces self-describing files that embed encoding parameters within a short header. This header distinguishes VMS from raw CVSD streams, letting playback tools process recordings without external configuration. The SoX audio toolkit provides native read and write support, making it straightforward to convert VMS recordings into WAV or other modern formats. A practical advantage is the format's small file size — CVSD compression keeps voice mail messages compact enough for systems with limited disk capacity, which was critical in early telephony infrastructure. The encoding degrades gracefully under noisy channel conditions, preserving speech intelligibility even when errors occur. Although VMS has been superseded by modern codecs in current voice messaging platforms, it remains relevant for recovering legacy voice mail archives.
Developer: SoX Contributors
Initial release: 1991

Frequently Asked Questions

Why convert CAVS to VMS?

If you only need the audio from a CAVS recording, converting to VMS strips the video and produces a lightweight audio file.

Which applications support VMS?

Voice messaging platforms and telephony tools support VMS audio file playback.

Can I convert several files at once?

Yes. Upload multiple CAVS files and extract VMS audio from each one in a single batch operation — fast and convenient.

Do I need to install anything?

Not at all. The converter runs in your web browser — no downloads, plugins, or desktop applications are required for the conversion.

Does it work on phones and tablets?

Yes. The converter runs in any modern mobile browser on iOS and Android devices, with the same functionality as desktop.

What happens to my uploaded files?

Uploaded CAVS files are deleted from our servers immediately after processing. Converted VMS files are auto-removed within 24 hours.