Abstract: A method of encoding a picture in an MPEG2 compliant digital video encoder. The method calculates a contrast function,Contrast=.SIGMA..vertline.P(j)-P(j+1).vertline.and thereafter calculates a quantization adjustment function therefromM(i+1)=?C(i+1)/C(i)!M(i),where C=Contrast, P(j) is the luminance or chrominance of the j.sup.th pixel, and M(i)is the average quantization of the i.sup.th picture. The quantization or picture type is adjusted in response to the contrast function, C.

Abstract: A method for spatial compression of a digital video picture to obtain the quantizer step size so as to avoid over "lossy" reconstruction and loss of detail. The first step is dividing the picture into a plurality of macroblocks, for example, 16.times.16 macroblocks, each macroblock having luminance or chrominance pixel blocks, for example four 8.times.8 pixel blocks. This is followed by multiplying each luminance pixel block by a modified frequency ordered Hadamard matrix to yield a first dimension of each luminance pixel block. The first dimension of each pixel block is then multiplied by the inverse of the modified frequency ordered Hadamard matrix to yield a second dimension of each luminance pixel block. The second dimension of the pixel luminance block is then weighted against a weight matrix, and the individual weighted terms are summed for each pixel block. The minimum of the weighted terms is selected. This minimum is used to detect the edge or texture of the macroblock, e.g.

Abstract: Method and apparatus for encoding a digital video image stream in an encoder. The encoding includes spatial compression of still images in the digital video image stream and temporal compression between the still images. The spatial compression is carried out by converting a time domain image of a macroblock to a frequency domain image of the macroblock, taking the discrete cosine transform of the frequency domain image, transforming the discrete cosine transformed macroblock image by a quantization factor, and run length encoding the quantized discrete cosine transformed macroblock image. The temporal compression is carried out by reconstructing the run length encoded, quantized, discrete cosine transformed image of the macroblock, searching for a best match macroblock, and constructing a motion vector between them. This forms a bitstream of runlength encoded, quantized, discrete cosine transformed macroblocks and of motion vectors.

Abstract: A method of Discrete Cosine Transform compression of a digital video image. In the method the Field Variance and Frame Variance are calculated. When the Field Variance is less than the Frame Variance, Field Discrete Cosine Transform type compression is performed. Alternatively, when the Frame Variance is less than the Field Variance, then a Frame Discrete Cosine Transform compression is performed.