RETURN Voice Digitization


Continuously Variable Slope Delta Modulation (CVSD)

The CVSD algorithm, like ADPCM, generates a code difference between the current input sample and a predicted value from past output. The general algorithm process is also similar to ADPCM, except that the input to the algorithm is ANALOG. (In ADPCM, the input to the algorithm is a PCM byte).

CVSD has some unique attributes:

  - Its analog nature results in implementation by CODEC.
  - Its 'single-bit' architecture is not well-suited for microprocessor
  - The 'sampling rate' is a direct function of the output digital bit rate.


While CVSD does not out-perform ADPCM, it can operate within a large range of bit rates; anywhere from 9.6 to 64 KBPS. This is ideal for ‘tactical’ environments, or in networks where very dynamic datalink usage or network configuration activity occurs. However, most commercially available CVSD implementations are ‘optimized’ for operation at 32 KBPS or 24 KBPS.

CVSD, though ‘well known’, is NOT STANDARDIZED. Thus, all CVSD implementations are of a ‘proprietary’ nature.