Patent ID: 6104434
Filing Date: 2000-08-15
Classification: H04N

Abstract:
A video coding apparatus for performing a predictive coding of digital video input signals, comprising:(a) resolution determination means for selecting a picture resolution to be used in a video coding of a source picture of a current frame, the picture resolution being either a low resolution or a high resolution;(b) decoded picture storage means for storing a past decoded picture reproduced in a previous frame;(c) prediction parameter calculation means, coupled to said resolution determination means, for determining which of two coding schemes should be used to encode individual blocks, by comparing the source picture of the current frame with the past decoded picture stored in said decoded picture storage means, and also for calculating motion vectors of the blocks in the source picture, whereinsaid two coding schemes include an intraframe coding and an interframe coding, andsaid blocks are defined by partitioning a given picture into pieces according to the picture resolution determined by said resolution determination means;(d) prediction picture generation means for producing a prediction picture through calculation of pixel values on a block-by-block basis, said calculation of the pixel values includingassignment of zeros to pixel values of the blocks subject to the intraframe coding, andcalculation of the pixel values of the other blocks subject to the interframe coding, based on the past decoded picture stored in said decoded picture storage means and the motion vectors obtained by said prediction parameter calculation means;(e) prediction error signal generation means for producing a prediction error signal for each block by calculating differences between the source picture and the prediction picture;(f) first resolution conversion means for downsampling the prediction error signal produced by said prediction error signal generation means to provide the low resolution, depending upon the picture resolution determined by said resolution determination means;(g) orthogonal transformation/quantization means for applying an orthogonal transformation process and a quantization process to the prediction error signal processed by said first resolution conversion means;(h) code allocation means for outputting a code word relevant to a given set of data, which code word is retrieved out of a predefined code word table, whereinsaid given set of data includes at least the output of said orthogonal transformation/quantization means, the picture resolution determined by said resolution determine means, the coding scheme determined by said prediction parameter calculation means, and the motion vectors calculated by said prediction parameter calculation means, andsaid predetermined code word table contains a plurality of cord words previously assigned to each possible combination of the given set of data;(i) dequantization/inverse orthogonal transformation means for applying a dequantization process and an inverse orthogonal transformation process to the output of said orthogonal transformation/quantization means to reproduce the prediction error signal;(j) second resolution conversion means for applying an upsampling process to the reproduced prediction error signal sent from said dequantization/inverse orthogonal transformation means to provide the high resolution, if the reproduced prediction error signal has the low resolution processed by said first resolution conversion means, whereinsaid upsampling process, when calculating a pixel value in a block that is subject to one of the two coding schemes, does not refer to any pixels that belong to any other block adjacent to the block of interest if the adjacent block is subject to the other coding scheme, but refers at least to the pixels belonging to the block of interest; and(k) decoded picture generation means for constructing a decoded picture by adding the reproduced prediction error signal processed by said second resolution conversion means to the prediction picture produced by said prediction picture generation means, and for outputting the decoded picture to said decoded picture storage means.