What is the CVS file format?
.cvs is a raw audio file encoded with CVSD (Continuously Variable Slope Delta modulation), a 1-bit differential speech-compression technique developed at Bell Labs in 1969. In CVSD encoding, each bit represents a step up or down in amplitude; the step size (slope) adapts automatically to the signal's dynamics, giving the method its name.
The file is a headerless raw bitstream - no file header, no magic bytes, and no embedded metadata. Format identification relies entirely on the .cvs extension and prior knowledge of the bitrate and sample rate (typically 8 kHz, yielding 8 kbps). Byte order follows big-endian MSB-first convention per the CVSD standard.
The SoX (Sound eXchange) command-line audio tool popularized the .cvs extension for filtered CVSD; SoX also accepts .cvsd as an alias and uses .cvu for the unfiltered variant. Conversion requires specifying the encoding explicitly - for example: sox -t cvs input.cvs -r 8000 output.wav to produce a standard WAV file.
CVSD found widespread use in military radios, two-way radio equipment, and legacy telephony/voicemail systems. It has largely been replaced by G.711 PCM mu-law/A-law and modern codecs like Opus for new deployments. Despite the near-identical extension, .cvs is entirely unrelated to CSV spreadsheet text files.
Security & safety
RISK: LOWRaw audio bitstream; no known security risk from opening in SoX or Audacity. Treat like any unknown audio file from untrusted sources.
Format details
in a nutshell- Canvas Drawing File (ACD Systems) - ACD Systems' Canvas vector-graphics application uses .cvs for drawing/illustration files - completely unrelated to CVSD audio.
- Concurrent Versions System repository file - CVS (Concurrent Versions System) source-control system uses .cvs for various repository metadata files - unrelated to audio.
Programs that open CVS files
Windows2 apps
SoX (Sound eXchange)
Open-source sox input.cvs -r 8000 -e cvsd output.wav - specify sample rate explicitly (e.g. -r 8000) since the file is headerless.
Audacity (via FFmpeg)
Open-source Use File > Import > Raw Data, set encoding to CVSD, sample rate 8000 Hz. Requires knowing the recording parameters. 
macOS1 app
SoX (Sound eXchange)
Open-source Install via Homebrew (brew install sox), then: sox input.cvs -r 8000 -e cvsd output.wav 
Linux1 app
Technical details
deep spec| Encoding | CVSD (Continuously Variable Slope Delta modulation), 1-bit differential |
| Byte order | Big-endian (MSB-first, per CVSD standard) |
| Container | None - headerless raw bitstream |
| Sample rate | 8 kHz (standard voice; SoX `.cvu` variant supports variable rates) |
| Bit depth | 1 bit per sample (delta modulation stream) |
| Bit rate | 8 kbps at standard 8 kHz rate |
| Typical file size | 8 KB - 8 MB (approx. 60 KB per minute at 8 kHz) |
| Magic bytes | None (headerless; no file signature) |
| MIME type | `audio/x-cvs` |
| SoX aliases | `.cvsd` (filtered CVSD), `.cvu` (unfiltered CVSD variant) |
| Compression type | Lossy - differential delta encoding with adaptive slope |
| Application domain | Military radios, two-way radio, legacy telephony and voicemail systems |
| Standard origin | Bell Labs, 1969; `.cvs` extension popularized by SoX in the 1990s |
| Released | CVSD standard: 1969 (Bell Labs); SoX support: 1990s |
| Latest version | N/A (raw format, no versioning) |
| Open standard | Yes · royalty-free |
| Specification | sox.sourceforge.net |
CVS conversions
Community Q&A
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