A color image encoder comprises a block converter for dividing a digital color video signal, which is composed of a Y signal and R-Y and B-Y signals, into blocks for the respective signals; an orthogonal transformer for orthogonally transforming the digital image video signal divided into the blocks, for each block, to produce orthogonal transform coefficients; a quantizer for quantizing the orthogonal transform coefficients; a variable length encoder for coding the quantized orthogonal transform coefficients to produce a code sequence; a generator code length counter for counting the length of the code sequence; a chrominance signal inspection circuit for calculating an absolute value of a difference between an average of pixel values in each block of at least one of the two chrominance signals and a value in an achromatic level of the chrominance signal, detecting a maximum value from the absolute values obtained in a unit of a collection of pixels for which a quantization scale used in the quantizer is to be changed, and comparing the maximum value with a prescribed threshold value; and a quantization scale decision circuit for providing a real quantization scale used in the quantizer on the basis of the length of the code sequence counted by the generator code length counter when the chrominance signal inspection circuit judges that the maximum value is smaller than the threshold value, and providing a real quantization scale used in the quantizer so that it becomes smaller than the interim quantization scale which is obtained on the basis of the length of the code sequence counted by the generator code length counter when the chrominance signal inspection circuit judges that the maximum value is larger than the threshold value. Therefore, a block for which the quantization scale is to be made small can be selected by a simple threshold setting for the chrominance signal, whereby visually conspicuous deterioration of image quality can be reduced.
In an electronic still camera, a compression coefficient estimating unit performs preencoding using only an LA component of FBTC compressed data read from an image memory, and estimates an optimal compression ratio based on the result of preencoding. Thereafter, JPEG encoder performs JPEG compression on the image data applied from FBTC decoder with the estimated compression coefficient, and transfers the result to a recording apparatus. As compared with the prior art in which image data is directly preencoded, the time for preencoding can be significantly reduced and image memory requires smaller capacity.
The invention relates to the use of a human visual system (HVS) in a video encoder. A coding method and device are proposed in which the allocation of bits are efficiently modified over each current picture according to the fact that the eye is more or less sensitive to each area of said picture. In view of said re-allocation, a specific computation of so-called perceptual coefficients is proposed and leads to an improved visual quality, while ensuring that the global rate control performance of the encoder is not modified.
The method of encoding divides the image into a number of blocks, which are then transformed (200), in accordance with a linear transform, into blocks of transform coefficients. The transform coefficients are rearranged (202) into a set of groups, wherein subsets of the groups of coefficients are capable of being inversed transformed to reproduce the image or a resolution thereof. The groups (203) are then encoded in turn. In the method of decoding, a user first selects a resolution mode and the method decodes (300) a predetermined number of groups in response to said resolution mode. The method then rearranges (301) the decoded groups to form blocks of transform coefficients, wherein the arrangement is determined in response to the resolution mode. The method then inverse transforms said rearrangement (303), if necessary, wherein the inverse transform is dependent on the resolution mode and combines the blocks of pixels to reconstitute the image or a resolution thereof.
An image generator is organized into a plurality of rendering engines, each of which renders an image of a part scene and provides the part image to a merge engine associated with that rendering engine. The image is a part image in that it usually contains less than all of the objects in the image to be rendered. The merge engine merges the part image from its associated rendering engine with the part image provided by a prior merge engine and provides the merged part image to a next merge engine. One or more merge engines are designated the output merge engines and these output merge engines output a merged part image that is (a portion of) the ultimate output of the image generator, the full rendered image. Each merge engine performs its merge process on the pixels it has from its rendering engine and from its prior neighbor merge engine, in a pipelined manner and without necessarily waiting for all of the pixels of the part image or the merged part image.
A picture signal encoding apparatus on which, even if a picture is not uniform in picture pattern, the picture can be rendered substantially uniform in picture quality, the volume of bits occupying a virtual buffer is stabilized, deterioration in picture quality is rendered less visible and in which stable rate control is assured. The picture signal encoding apparatus, dividing a picture making up moving picture signals into plural macro-blocks MB and encoding the signals from one macro-block to another, includes a relative coding difficulty calculating circuit for calculating the relative coding difficulty from one macro-block to another MB, and a characteristic value calculating circuit for calculating the weighting coefficients (characteristic values) specifying visibility degree of picture quality deterioration from one macro-block MB to another. The picture signal encoding apparatus also includes a bit rate controller for calculating the quantization scale for encoding each macro-block MB using the complexity degree and the volume of allocated bits for macro-block-based encoding.
