MPEG-2 Video Coding - Digital Video and Audio Broadcasting Technology - page 115

between these types of picture areas and to transmit only the difference,
i.e. the delta value, from one frame to the next. This particular method of
redundancy reduction, which is based on a method which has been known
for a long time, is called differential pulse code modulation (DPCM).

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Fig. 7.8. Differential Pulse Code Modulation with reference values

Fig. 7.9. Dividing a picture into blocks and macroblocks

What then is differential pulse code modulation? If a continuous analog
signal is sampled and digitized, discrete values, i.e. values which are no
longer continuous, are obtained at equidistant time intervals (Fig.7.5.).
These values can be represented as pulses spaced apart at equidistant inter-
vals, which corresponds to a pulse code modulation. The height of each