Some properties of differential PCM schemes

Two differential PCM schemes are analysed and compared with PCM. In D*PCM the quantization is done after the prediction, while the quantization is included in the prediction process in the case of the well-known DPCM. For both coding schemes a gain formula will be given. The formula is good both for arbitrary probability density functions and an arbitrary setting of the predictor coefficients. It will be shown that D*PCM schemes do not have a gain as compared to the much simpler implemented PCM scheme if gaussian signals are quantized. Additionally the influence of channel errors on the variance of the overall error will be given for both differential PCM schemes. It will be shown that, at least for gaussian signals, the effect of channel errors on the overall error is not greater than that in PCM.