Survey of Dirac: A Wavelet Based Video Codec for Multiparty Video Conferencing and Broadcasting - Intelligent Video Event Analysis and Understanding - page 212

based codec's are the most popular, in Figure 1 the DCT based encoder block
diagram has been shown. The three main building blocks are DCT, quantization
and VLC coding. For intra block, the block is DCT transformed, quantized and
then VLC coded. There is no need to keep the reference of intra coded block. For
inter block, motion vectors are achieved by performing motion estimation. The
motion vectors are applied on the reference block, stored in the frame store. The
difference block of the current and motion compensated block is DCT
transformed, quantized and VLC coded. The motion vectors are also VLC coded
and are sent along with difference block coded data. The difference block data
after quantization is inverse quantized and inverse DCT transformed. The motion
compensated block is also added to this block and then stored in the frame store
for future reference.
Fig. 1 DCT encoder block diagram [11]
In Figure 2, DCT decoder block diagram has been shown. For intra block, the
coded bit stream is inverse VLC coded, inverse quantized and then inverse DCT
transformed for reconstruction of block. For inter block, the coded bit stream is
inverse VLC coded. The motion compensation is performed on the reference block
by applying motion vectors, stored in the previous frame memory. The difference
block after inverse VLC coded is inverse quantized and IDCT transform and then
added to the motion compensated block to reconstruct the block. The reconstructed
block is stored in the previous frame memory for future reference.
Fig. 2 DCT decoder block diagram [11]