Abstract: A device for data compression includes a domain transformer unit, a classifying unit, a variable length encoder, a fixed length encoder and a memory unit. The domain transformer unit transforms time-domain data into frequency-domain data. The classifying unit determines an encoding type of the frequency-domain data based on occurrence probability of the frequency-domain data. The variable length encoder encodes first frequency-domain data that are determined to be encoded by variable length coding. The fixed length encoder encodes second frequency-domain data that are determined to be encoded by fixed length coding. The memory unit stores the encoded first and second frequency-domain data by relocating the encoded first and second frequency-domain data such that the encoded first frequency-domain data are placed adjacently and the encoded second frequency-domain data are placed adjacently. Therefore, the time for decoding the corresponding data may be reduced.

Abstract: An image coding method and apparatus considering human visual characteristics are provided. The image coding method comprises (a) modeling image quality distribution of an input image in units of scenes such that the quality of an image input in units of scenes is gradually lowered from a region of interest to a background region, (b) determining a quantization parameter of each region constituting one scene according to the result of modeling of image quality distribution, (c) quantizing image data in accordance with the quantization parameter, and (d) coding entropy of the quantized image data.

Abstract: An image coding method and apparatus considering human visual characteristics are provided. The image coding method comprises (a) modeling image quality distribution of an input image in units of scenes such that the quality of an image input in units of scenes is gradually lowered from a region of interest to a background region, (b) determining a quantization parameter of each region constituting one scene according to the result of modeling of image quality distribution, (c) quantizing image data in accordance with the quantization parameter, and (d) coding entropy of the quantized image data.

Abstract: An image coding method and apparatus considering human visual characteristics are provided. The image coding method comprises (a) modeling image quality distribution of an input image in units of scenes such that the quality of an image input in units of scenes is gradually lowered from a region of interest to a background region, (b) determining a quantization parameter of each region constituting one scene according to the result of modeling of image quality distribution, (c) quantizing image data in accordance with the quantization parameter, and (d) coding entropy of the quantized image data.

Abstract: An image coding method and apparatus considering human visual characteristics are provided. The image coding method comprises (a) modeling image quality distribution of an input image in units of scenes such that the quality of an image input in units of scenes is gradually lowered from a region of interest to a background region, (b) determining a quantization parameter of each region constituting one scene according to the result of modeling of image quality distribution, (c) quantizing image data in accordance with the quantization parameter, and (d) coding entropy of the quantized image data.

Abstract: A method and apparatus for redundant image encoding and decoding, in which using a slice structure used for image encoding part of an image is redundantly encoded and decoded are provided. The apparatus for redundant image encoding includes a slice modeling unit which determines the structures of slices to be used in encoding the image and regions to be redundantly encoded so that image data of a predetermined region of the image to be redundantly encoded is contained in a plurality of slices, a slice allocation unit which allocates image data of each region of an image to the plurality of slices, a picture header encoding unit which encodes information required to decode the plurality of encoded slices and generates picture information, and a slice encoding unit which encodes the image in units of slices according to the picture header information.

Abstract: An apparatus and method for enhancing the quality of reproduced images are provided. More specifically, provided are an apparatus and method for enhancing the quality of reproduced, progressive images, which are capable of obtaining more natural and smoother progressive images and preventing such problems as blurry colors and aliased images that could be brought about in the process of converting interlaced images into progressive images.

Abstract: An image coding method and apparatus considering human visual characteristics are provided. The image coding method comprises (a) modeling image quality distribution of an input image in units of scenes such that the quality of an image input in units of scenes is gradually lowered from a region of interest to a background region, (b) determining a quantization parameter of each region constituting one scene according to the result of modeling of image quality distribution, (c) quantizing image data in accordance with the quantization parameter, and (d) coding entropy of the quantized image data.

Abstract: An optimal scanning method for coding/decoding an image signal is provided. In a method of coding an image signal through a discrete cosine transform, at least one is selected among a plurality of reference blocks. A scanning order in which to scan blocks to be coded of the reference blocks is generated and the blocks to be coded are scanned in the order of the generated scanning order. The at least one selected reference block is temporally or spatially adjacent to the block to be coded. When the blocks to be coded are scanned, probabilities that non-zero coefficients occur are obtained from the at least one selected reference block, and the scanning order is determined in descending order starting from the highest probability. Here, the scanning order is generated to be a zigzag scanning order if the probabilities are identical. The optimal scanning method increases signal compression efficiency.

Abstract: Correct motion estimation is performed by preventing an adverse effect due to the variation of lighting conditions when a motion estimation is performed in a motion image device.

Abstract: A discrete cosine transform (DCT) coefficient prediction method and a DCT coefficient encoding method are provided. For the prediction of AC coefficients, location information of the nonzero AC coefficients is used. Then, the AC coefficients are divided into the vertical and horizontal component areas, and a remaining area, and variable modified zigzag scanning is applied for encoding. The performance of the AC coefficient prediction coding is improved as the absolute values of the predicted coefficients are small, and as the number of coefficients of value zero increases. The coefficients of value zero may be predicted as nonzero, so these coefficients are eliminated from the prediction. On the other hand, when using the characteristics of the adjacent blocks in a spatial domain, a larger weighted value is applied to the pixel values which are the nearest to the current block, thereby improving the prediction characteristics for DC/AC coefficients in a discrete cosine transform (DCT) domain.

Abstract: In a moving picture coding method and apparatus for low bit rate systems using dynamic motion estimation, a shape component of the moving object for analysis can be extracted together with a motion component, thereby reducing bit generation and reducing degradation of a reconstructed image. The shape component includes location information for a group of blocks which comprise the object for analysis. The motion component includes a displacement and a rotation angle applicable to the group of blocks.

Abstract: Baseline-based contour coding and decoding methods are provided. The coding method comprises the steps of determining a baseline of a still image or moving image object and a predetermined sampling interval, sampling the contour of the object according to the baseline and the sampling interval and extracting contour sample data, extracting utmost contour sample data of the object from the contour sample data, and calculating a difference between the utmost contour sample data and the contour sample data and extracting error sample data. Using a characteristics of contour data having a gentle change, the still image contour coding using transformation or the moving image contour coding using transformation and motion estimation guarantees excellent reconstruction even with a small amount of generated bit.

Abstract: A centroid-based object contour encoding method and device for encoding still images and moving pictures by rendering a more accurate contour representation with increased compression. The method includes the determination of a centroid and incrementing angle, the determination of distances between the centroid and boundary pixels on an object, and the encoding of the information determined. For moving pictures, the difference between the data of a current frame and the data of a previous frame are encoded by discrete cosine transforming and variable-length coding of the difference data.

Abstract: The present invention relating to a method of video coding associated with processing accumulated errors and a encoder therefor, the method comprising the steps of: (a) generating motion vectors of an input image in a predetermined unit and the difference image between an image of filtering a motion-compensated image on a reconstructed previous frame and the input image on current frame, and then performing discrete cosine transform (DCT), quantization and variable length coding on the difference image; (b) generating the motion-compensated image on the reconstructed previous frame from the reconstructed previous frame and the motion vectors; and (c) filtering off accumulated errors while preserving the edges within the motion-compensated image on the reconstructed previous frame. Therefore, random distributed noises due to accumulated errors can be removed and bit generation amounts by filtering off random accumulated errors with a high frequency characteristics before coding can be reduced.

Abstract: An image compression method employing a conditional quadtree split method includes inputting image data in frame or field units as blocks having a predetermined size; generating an average value for all of the pixels in each block and a sub-block code value for determining whether to perform sequential quad-splitting operations on the block into a suitable sub-block according to image type; and outputting a quadtree map drawn according to the sub-block code value and the average value of each block, as a bit stream. An apparatus employing the method can transmit good quality image data having no distortion at a high transmission rate.

Abstract: A method for encoding a motion image and an apparatus therefor includes first and second buffers, a motion estimator/compensator, an MC error generator/divider, first and second quadtree processors, a multiplexer, a quantizer, a variable length coder, a bit rate controller, an inverse quantizer, first and second inverse quadtree processors, and an adder/filter. Here, MC errors generated after motion compensation are divided into accumulated and compensation errors according to the characteristics, and then encoded. Thus, bit generation can be reduced compared with the conventional method, picture quality can be improved, and a process structure can be simplified.

Abstract: A bi-directional motion estimation method and apparatus thereof in a low bit-rate moving video codec system, for filtering motion vectors by performing a bi-directional motion estimation in units of objects having the same motion in a constant domain and for compensating the motion using the motion vectors generated as the result of forward or backward motion prediction in accordance with the motion prediction mode of previously set frames, can determine the precise motion vector compared to the existing block matching algorithm and depict the inter-frame motion with a smaller amount of information. Therefore, markedly less data (for compression) is used and reconstructed picture quality is improved.