d by the quantization motion vectors is called block-matching motion CHAPTER 7.4 Video compression estimation. The method uses the current frame Ik the discrete wavelet transform methods. The wavelet and the previous reconstructed frame Ik-1 as input. transform decomposes a bandwidth limited signal into Each block in the previous frame is assumed to have a multiresolution representation. The multiresolution a displacement that can be found by searching for it decomposition makes the wavelet transform an excellent in the current frame. The search is usually signal analysis tool because signal characteristics can be constrained to be within a reasonable neighborhood viewed in a variety of time-frequency or space-frequency SO as to minimize the complexity of the operation. scales. The wavelet transform is implemented in practice Search matching is usually based on a minimum MSE via the use of multiresolution or subband filterbanks [6]. or MAE criteria. When a match is found, the pixel The wavelet filterbank is well suited for video encoding displacement is used to encode the particular block. because of its ability to adapt to the multiresolution If a search does not meet a minimum MSE or MAE characteristics of video signals. Wavelet transform threshold criteria, the motion compensator will in- encodings are naturally hierarchic in their time-fre- dicate that the current block is to be spatially quency representation and easily adaptable for pro- encoded using Intraframe mode. gressive transmission [7]. They have also been shown to Motion compensation - The motion compensator possess excellent bit rate-distortion characteristics. makes use of the current frame motion estimates Direct three dimensional video compression systems MVk and the previously reconstructed frame Ik-1 to suffer from a major drawback for real-time encoding generate the current frame prediction Pk. The cur- and transmission. In order to encode a sequence of rent frame prediction is constructed by placing the images in one operation, the sequence