Differential PCM (continued)

The reconstructed is also needed at the transmitter, since it is used in coding the pixel intensities which have not yet been coded. The dotted line in Fig ( ) indicates that is computed to code these pixel intensities. As in DM, previously reconstructed values are used to avoid propagating the quantisation noise .

Equations that govern DPCM system are:

where quantisation noise

DPCM reduces PCM when is set to zero

In DPCM, is predicted as

where Ra is the region of over which is nonzero.

(continued in the next slide)