ABSTRACT
The G.711 PCM standard we discussed in the last chapter employs a memoryless quantizer that acts on the instantaneous values of the signal without taking advantage of the correlation that may exist between adjacent samples. Since neighboring speech samples are generally correlated, the variance of the difference between successive samples will be smaller than that of the original signal. It would therefore be advantageous to quantize the difference signal x(n) − x(n − 1) instead of the instantaneous sample values x(n). This is the basic idea behind differential coding.
