Apparatus for encoding a video signal by using modified block truncation and contour coding methods

An apparatus for encoding a video signal having a plurality of video frames, each of the video frames containing pixels therein, said apparatus comprising:

• means for comparing an intensity value of each pixel contained in a video frame with a threshold value and classifying each pixel into one of two groups based on a comparison result between the intensity value of each pixel and the threshold value to thereby provide a binary frame, the binary frame including a plurality of regions, each of the regions consisting of continuous pixels classified into one of the two groups;
• means for coding the binary frame to thereby provide region information including contour information and binary information, the contour information representing position data of pixels on a contour of each region and the binary information representing a group into which pixels included in each region are classified;
• means for dividing the binary frame into a multiplicity of non-overlapping binary blocks, each of the binary blocks containing K.times.K pixels with K being a positive integer larger than 1;
• means, for each binary block, for determining the number L of pixels classified into one of the two groups and included in each binary block;
• means, for each binary block, for generating a control signal representing whether or not all of the K.times.K pixels in each binary block belong to only one of the two groups;
• means for dividing the video frame into a multiplicity of non-overlapping video blocks of K.times.K pixels, each video block corresponding to one of the binary blocks, and providing, for each video block, a mean value and two reconstruction values based on intensity values of the K.times.K pixels therein and the number L determined for a corresponding binary block thereof;
• and
• means, in response to the control signal, for selecting the mean value if the control signal represents that all of the pixels in the corresponding binary block belong to one of the two groups and selecting the two reconstruction values if otherwise, to thereby generate a selected output for each video block.