 Only the (smaller) amount of difference between each DC value and the value of the DC coefficient in the block to its left needs to be represented in the final bitstream.Additionally, the frequency conversion performed by applying the DCT provides a statistical decorrelation function to efficiently concentrate the signal into fewer high-amplitude values prior to applying quantization (see below).Quantization is, essentially, the process of reducing the accuracy of a signal, by dividing it by some larger step size and rounding to an integer value (i.e.