SLN to CVS Converter

Encode Asterisk SLN telephony audio as CVS voice format

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Voice System Compatible

Move SLN telephony audio into CVS format — designed for voice communication systems using delta modulation.

Compact Voice Files

CVS delta modulation produces very small voice files from your SLN recordings — ideal for bandwidth-limited systems.

Private Processing

Your PBX recordings stay confidential. Source files deleted post-conversion, outputs purged within 24 hours.

How to convert SLN 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

SLN (Signed Linear) is a headerless raw audio format storing 16-bit signed linear PCM samples at 8000 Hz mono, most closely associated with Asterisk — the open-source PBX framework developed by Digium (now Sangoma Technologies). Within Asterisk, SLN serves as the native internal audio representation: every codec transcoding operation passes through signed linear as an intermediate step. This makes SLN the backbone of Asterisk's codec translation architecture. The format contains nothing but raw samples — no headers, no metadata, no framing — so parameters must be known in advance. While this lack of self-description might seem limiting, it is actually an advantage in telephony where sample format is fixed by convention and every overhead byte matters across thousands of simultaneous channels. The 8000 Hz rate aligns with the G.711 standard for traditional telephony, capturing the full 300-3400 Hz voice band. Asterisk also supports extended variants (sln16, sln32, sln48) for wideband audio. SLN files require no decoding — just direct memory mapping — making them ideal for real-time mixing, conferencing, and prompt playback in high-density VoIP environments.
Initial release: 1999
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 SLN to CVS?

CVS uses continuously variable slope delta modulation for voice. Converting SLN to CVS serves specific telephony and embedded voice systems.

What uses CVS files?

CVS is handled by SoX and certain telephony hardware and embedded systems that use CVSD encoding for voice data.

Is CVS a compressed format?

Yes — CVS uses delta modulation compression optimized for voice signals, producing compact files at the cost of fidelity for non-voice audio.

Can I convert several SLN files?

Upload multiple SLN recordings at once and convert them all to CVS in a single batch process.

Is my data safe?

SLN uploads are deleted after conversion, and CVS outputs are purged from our servers within 24 hours.