VOX to CVSD Converter

Re-encode Dialogic VOX as CVSD modulation audio

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Secure Voice Format

CVSD is the format of military secure voice systems. Your VOX recordings enter a hardened communication ecosystem.

Commercial to Military

Bridge Dialogic IVR telephony and military voice communications with a single conversion.

Online Encoding

CVSD encoding runs on our servers. No military-grade software needed on your end.

How to convert VOX to CVSD

1

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

2

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

3

Let the file convert and you can download your cvsd 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
CVSD (Continuously Variable Slope Delta modulation) is a voice digitization method standardized for military and telephony use by NATO and the CCITT during the 1970s. It encodes differences between consecutive samples as a single bit — 1 if the current sample exceeds the prediction, 0 otherwise — while a syllabic companding filter adjusts step size by monitoring runs of identical bits. Operating at 16 to 64 kbps, CVSD balances voice intelligibility against bandwidth, making it the encoding of choice for secure military links and tactical radio systems. The bitstream can be decoded with straightforward hardware, originally built into dedicated integrated circuits. One advantage is implementation simplicity — encoders and decoders need minimal resources, enabling real-time processing on low-power embedded hardware. Robustness under noisy conditions is another strength, as single-bit errors affect only local samples rather than corrupting entire frames. SoX provides software encoding and decoding support, letting modern systems work with legacy CVSD recordings from military archives and vintage telecommunications infrastructure.
Developer: CCITT / NATO
Initial release: 1970

Frequently Asked Questions

Why convert VOX to CVSD?

CVSD is used in military secure voice and Bluetooth. Converting VOX adapts commercial telephony audio for these specialized systems.

What can open CVSD files?

SoX, military communication equipment, and some Bluetooth implementations process CVSD.

How do VOX and CVSD compare?

VOX uses OKI ADPCM for commercial IVR; CVSD uses delta modulation for military voice. Different compression, different ecosystems.

Is CVSD used in Bluetooth?

Older Bluetooth SCO profiles use CVSD for voice — converting VOX to CVSD can target these implementations.

What quality to expect?

Both formats are voice-grade. CVSD delivers telephone-quality speech with good noise resilience.