| 摘要 |
<p>In a coder frames of a digital video signal are scanned in a pseudo-random order to get blocks of pixels, motion vectors are estimated and block errors are calculated, thereby providing an intra/inter decision signal and intraframe-blocks of pixel values or motion compensated interframe-blocks of pixel difference values depending on the result of the block error. The blocks of pixel values ond pixel difference values, respectively, are transformed with a DCT to blocks of coefficients, coded together with the motion vectors in a Huffman coder with variable wordlength. The resulting groups of coded coefficients are quantized individually by the use of a quantization level and the coded coefficients of the group are individually quantized by the use of a quantization matrix, controlled by the fullness of a buffer. In a decoder groups of coded coefficients which belong to blocks of pixels are de-quantized individually by the use of an encoding quantization level and each coded coefficient of each group is de-quantized individually by the inverse use of an encoding quantization matrix, controlled by the fullness of a buffer. The groups of coded coefficients and motion vectors are decoded in a Huffman decoder with variable wordlength, thereby providing blocks of decoded coefficients. The blocks of decoded coefficients are transformed with an inverse DCT to pixel values and pixel difference values, respectively, out of which blocks of pixels out of intraframe-blocks of pixel values and motion compensated interframe-blocks of pixel difference values, respectively, are generated depending on an intra/inter decision signal, thereby evaluating the motion vectors. The blocks of pixels are inserted again in frames of a digital video signal in an according pseudo-random order. Because of the pseudo-random scanning the quantization level of the blocks of the coded digital image frames is spatially distributed and the visibility of a varying picture quality within a frame is reduced.</p> |
