VOX to CVS Converter

Re-encode Dialogic VOX audio as CVSD telephony

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Telephony to Military

Bridge commercial IVR audio (VOX) and military voice systems (CVS) — two telephony worlds connected by a single conversion.

Cloud Encoding

No SoX installation needed. The CVSD encoding runs on our servers without any local setup.

Confidential Handling

Telephony audio is sensitive. Uploaded VOX files are deleted immediately, and CVS outputs are purged within 24 hours.

How to convert VOX to CVS

1

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

2

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

3

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

About formats

VOX is a headerless audio format built around Dialogic ADPCM encoding, widely adopted in telephony, interactive voice response (IVR) systems, and voice mail platforms since the 1980s. Each audio sample is compressed into 4 bits using an algorithm developed by Oki Electric and implemented in hardware on Dialogic Corporation's telephony interface cards. VOX files typically use a sampling rate of 6000 or 8000 Hz, producing extremely compact recordings optimized for speech intelligibility rather than musical fidelity. Because the format carries no header, playback software must know the sample rate and encoding parameters in advance — a trade-off that reduces overhead but demands careful file management. The primary advantage of VOX is storage efficiency: a one-minute voice recording at 8 kHz occupies roughly 240 KB, making it practical for systems storing thousands of prompts. Dialogic ADPCM conforms to the ITU-T G.726 standard, ensuring interoperability across telephony equipment from different vendors. Even as modern call centers migrate to IP-based systems with codecs like Opus), vast libraries of VOX recordings persist in legacy IVR deployments and compliance archives worldwide.
Initial release: 1983
CVS is a telephony audio encoding based on Continuously Variable Slope Delta modulation, representing voice through a 1-bit delta scheme where step size adapts to track input amplitude. Developed within CCITT (now ITU-T) standards during the 1970s, CVS encodes by comparing each sample to the previous one and outputting a single bit — up or down — with slope magnitude adjusting based on recent bit patterns. This yields extremely low bit rates, typically 16 kbps at 8 kHz sampling, efficient for narrowband voice over constrained channels. CVS files store signed delta-encoded data and are commonly processed using tools like SoX. A significant advantage is bandwidth economy: the 1-bit-per-sample approach demands minimal transmission capacity, essential for military radio links and early digital telephone infrastructure. The adaptive slope mechanism also prevents overload distortion on rapidly changing signals while keeping granular noise acceptable during quiet passages. Though modern wideband codecs have superseded CVS, it retains historical importance and niche utility in legacy telephony and embedded communication devices.
Developer: CCITT / ITU-T
Initial release: 1970

Frequently Asked Questions

Why convert VOX to CVS?

CVS uses CVSD modulation for military and specialized telephony. Converting VOX to CVS adapts call center audio for secure voice systems.

What can open CVS files?

SoX and specialized military communication equipment process CVS files. It is not a consumer audio format.

Are VOX and CVS both telephony formats?

Yes, but they serve different sectors. VOX dominates in commercial IVR; CVS targets military and specialized secure voice communications.

Is the conversion lossy?

Both formats use lossy compression optimized for speech. Converting between them may introduce minimal additional artifacts.

Can I process multiple files?

Upload a batch of VOX recordings and convert them all to CVS simultaneously — efficient for preparing audio for telecom deployments.

VOX to CVS Quality Rating

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