What Is Differential Pulse Code Modulation?

Differential pulse code modulation is a technique of analog to digital signal conversion. This technique samples the analog signal and then quantizes the difference between the sampled value and its predicted value. It then encodes the signal to form a digital value.

Differential pulse code modulation includes sampling of the input signal at a constant sampling frequency. It then modulates the signal using pulse amplitude modulation. The predictor stores the sampled signal and later sends the signal through a differentiator. The differentiator does a comparison between the current and the previous sample signal. It then sends the difference for quantizing and encoding.

Differential pulse code modulation depends on the prediction technique. Better prediction techniques lead to better compression rates. At the receiver end, the signal has to be dequantized and then summed to the value stored in the predictor. Sending the signal through a low-pass filter then regenerates the original input signal.

The advantage of using differential pulse code modulation is that it reduces the bit rate for voice transmissions. This is because most source signals show a correlation between successive signals and hence the encoding uses a redundancy in sample values. DPCM is more efficient compared to pulse code modulation in terms of bandwidth utilization. The application of DPCM is primarily in voice transmissions.