Differential pulse-code modulation (DPCM) is an efficient digitization
technique for encoding speech signals. The two principal components of
a DPCM system are the quantizer and the predictor, either or both of
which can be adaptive. This thesis describes the investigation of
various differential pulse-code modulation systems. Initially, fixed,
i.e. time-invariant, predictors using long-term signal statistics of the
speech signal are examined. The performance of such a predictor in a
DPCM system having a fixed quantizer is studied. Then by replacing the
fixed predictor with one whose coefficients are calculated at fixed time
intervals, the performance of the encoder, in terms of signal to noise
ratio (SNR), is improved by 3-5 dB. A further improvement of 2–3 dB in
SNR is obtained when an adaptive quantizer is used in the DPCM system.
However, the block adaptive predictor requires the transmission of
prediction coefficients to the receiving end at the expense of an increase
in the channel band width. [Continues.]
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy at Loughborough University.