| 摘要 |
Video coding apparatus and decoding apparatus capable of reproducing decoded pictures without introducing unwanted noises, even if any considerable difference in pixel values or discontinuity exists at a certain block boundary. In a video coding apparatus employing predictive techniques, a dequantizer and an inverse DCT processor reproduce a prediction error signal from quantized transform coefficients. Here, a first resolution conversion unit (or downsampling unit) might have subsampled the original prediction error signal to reduce its picture resolution. If this is the case, a second resolution conversion unit (or upsampling unit) attempts to restore the original resolution of the prediction error signal by applying an upsampling process to the reproduced prediction error signal having the reduced resolution. In this upsampling process, each new pixel value in a certain block are calculated with reference to some surrounding pixels. The upsampling process, however, will not refer to the pixels belonging to any adjacent blocks that are subject to another coding scheme which is different from the coding scheme of the present block of interest. As an alternate arrangement, the upsampling process will entirely neglect the pixels in any other blocks but will refer only to the present block, block-by-block basis, comprising the substep of(b1) performing an upsampling process of each block with the low resolution to regain the high resolution, while not referring, when calculating a pixel value in a block that is subject to one of the coding schemes, 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 referring at least to the pixels belonging to the block of interest.
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