Patent ID: 8666182

Claim:
A method for generating a thumbnail image from H.264-based N×N video blocks constituting a video frame, the method comprising the steps of: (a) extracting prediction reference pixels for one of the N×N video blocks; (b) computing a DC coefficient of a prediction block for each unit video block constituting the N×N video block using the extracted prediction reference pixels of the N×N video block, based on an intra-prediction mode of the N×N video block; and (c) computing a DC coefficient of the N×N video block by adding the computed DC coefficient of the prediction block for each unit video block and a DC coefficient of a residual block for each unit video block, wherein next prediction reference pixels are computed by adding prediction pixels to residual pixels, the next prediction pixels are placed on right and bottom borders of each unit video block, wherein the residual pixels include pixels placed on the right and bottom borders of each unit video block and are computed using transform element values computed from a residual coefficient block W for each unit video block, wherein the transform element values include H 0 , H 1 , H 2 , H 3 , V 0 , V 1 , V 2 and V 3 generated by the following Equations 1 to 8: H 0 = W 00 - W 01 + W 02 - 1 2 ⁢ W 03 [ Equation ⁢ ⁢ 1 ] H 1 = W 10 - W 11 + W 12 - 1 2 ⁢ W 13 [ Equation ⁢ ⁢ 2 ] H 2 = W 20 - W 21 + W 22 - 1 2 ⁢ W 23 [ Equation ⁢ ⁢ 3 ] H 3 = W 30 - W 31 + W 32 - 1 2 ⁢ W 33 [ Equation ⁢ ⁢ 4 ] V 0 = W 00 - W 10 + W 20 - 1 2 ⁢ W 30 [ Equation ⁢ ⁢ 5 ] V 1 = W 01 - W 11 + W 21 - 1 2 ⁢ W 31 [ Equation ⁢ ⁢ 6 ] V 2 = W 02 - W 12 + W 22 - 1 2 ⁢ W 32 [ Equation ⁢ ⁢ 7 ] V 3 = W 03 - W 13 + W 23 - 1 2 ⁢ W 33 , and [ Equation ⁢ ⁢ 8 ] wherein the residual coefficient block W of a transform domain for the unit video block is expressed by the following Equation 9: W = [ W 00 W 01 W 02 W 03 W 10 W 11 W 12 W 13 W 20 W 21 W 22 W 23 W 30 W 31 W 32 W 33 ] . [ Equation ⁢ ⁢ 9 ]