An image compression system and method for compressing image data for transmission Each block and corresponding sub-blocks of pixel data is subjected to a discrete cosine transform (DCT) operation Varying levels of sub-blocks of resulting corresponding transform coefficients are selected for construction into a composite transform coefficient block corresponding to each input block of pixel data The selection of transform coefficient block size for the composite block is determined by a comparison process between transform block and sub-block coding efficiency The composite block is variable length coded to further reduce bit count in the compressed data

Adaptive block size image compression method and system

A method and apparatus for selecting a quantizer scale (170) to maintain the overall quality of the video image while optimizing the coding rate. A quantizer scale is selected for each macroblock such that the target bit rate for the picture is achieved while an optimal quantization scale ratio is maintained for successive macroblocks to produce a uniform visual quality over the entire picture. One embodiment applies the method to the frame level while another embodiment applies the method in conjunction with a wavelet transform.

Apparatus and method for optimizing the rate control in a coding system

An apparatus and method for encoding of a video picture is disclosed. The video picture has a plurality of pictures. The pictures each have a plurality of macroblocks. The macroblocks each have a plurality of sub-blocks. The apparatus comprising a first module configured to generate a transform coefficient C ij for each of the sub-blocks of the macroblock. The apparatus further comprises a second module configured to variably quantize the transform coefficient by a scaling factor Q p based on the complexity of the picture and any rate control requirements.

An apparatus and method for motion video encoding employing an adaptive quantizer

An improved technique for efficient frequency scaling wherein the number of coefficients to be included in each sub-block (e.g. 4x4) is selectable (201), and a code indicating the number of coefficients within each layer is inserted in the bitstream at the beginning of each encoded video sequence. This technique allows the original runs of zero coefficients in the highest resolution layer to remain intact by forming a sub-block for each scale from a selected number (201) of coefficients along a continuous scan. These sub-blocks may be decoded in a standard fashion, with an inverse discrete cosine transform applied to square sub-blocks obtained by the appropriate zero padding of and/or discarding of excess coefficients from each of the scales. This invention further improves coding efficiency by allowing an implicit end of block signal to separate blocks, making it unnecessary to transmit an explicit end of block signal in most cases.

Efficient frequency scalable video encoding with coefficient selection

A video compression system and method for compressing video data for transmission or storage by reducing the temporal redundancy in the video data is described. A frame of video data is divided into a variable number of blocks of pixel data of varying size, and each block of data is compared to a window of pixel data in a reference frame of pixel data, typically the previous frame. A best matched block of pixel data is selected from the window of pixel data in the reference frame, and a displacement vector is assigned to describe the selected block location in the reference frame relative to the current block of pixel data. The number and size of the blocks of pixel data are permitted to vary, in order to adapt to motion discontinuities in the sequential frames of pixel data. This is to allow prediction blocks of pixel data in the current frame to be smaller in areas of high activity, while maintaining high levels of compression, achieved by using larger prediction blocks, in areas of the frame with low levels of activity. A frame of predicted pixel data is assembled from variable size blocks of prediction data and subtracted from the current frame of pixel data. Only the residual difference, the displacement vectors and an indication of the block sizes used in the prediction are needed for transmission or storage.

Interframe video encoding and decoding system

An image data coding apparatus performs first and second coding processes. A controller outputs first and second control signals. An orthogonal transform circuit performs orthogonal transform on image data of one screen and generates an transformed output. A quantizing circuit quantizes the transformed output with a predetermined temporary first quantization width upon reception of the first control signal and generates a first quantized output, and quantizes the transformed output with an optimal second quantization width upon reception of the second control signal and generates a second quantized output. An entropy coding circuit codes the first quantized output and generates a first coded output, and codes the second quantized output and generates a second coded output. An amount-of-codes calculator calculates the amount of codes of the first coded output for each block and calculates the amount of codes of one screen based on the amount of codes for each block. An assigned-amount-of-codes determining circuit determines the amount of codes assigned to each block based on the amount of codes for each block and the amount of codes of the one screen, and the target amount of codes. A quantization width predicting circuit predicts the second quantization width based on the amount of codes of the one screen. A coding stop circuit supplies a coding stop signal to the entropy coding circuit when the amount of codes of the second coded output exceeds the assigned amount of codes.

Image data coding apparatus and coding method

An image data coding apparatus includes a preprocessing unit for executing preprocessing including compression for input image data in units of screens to generate a preprocessed output. A quantizing unit quantizes the preprocessed output with a predetermined quantization width to generate a quantized output. A variable-length coding unit executes variable-length coding for the quantized output. A target-amount-of-codes output unit outputs information concerning a target amount of codes corresponding to one screen. A quantization width predicting unit predicts a suitable quantization width on the basis of the information from the variable-length coding unit to supply information concerning the predicted quantization width to the quantizing unit. The quantizing unit quantizes the preprocessed output generated by the preprocessing unit with the predicted quantization width included in the information from the quantization width predicting unit.

Image data coding apparatus and method capable of controlling amount of codes

PURPOSE: To compress a picture into an object code quantity early and to obtain best picture quality by setting variably a quantization width of quantization to an optimum value in response to the object code quantity. CONSTITUTION: Upon the receipt of a picture data outputted from an orthogonal conversion circuit 4, a quantization circuit 6 multiplies a quantization width coefficient with the quantization width for each frequency component at a 1st quantization in response to the pickup mode to apply quantization of the conversion coefficient in the corrected quantization width. The quantization is implemented by using an optimum quantization coefficient decided by a preceding processing at a 2nd time. A quantization width prediction circuit 12 receives information of object code quantity from a control circuit 18 at the start of a 1st path and sets the initial value of the quantization width coefficient to output the result to the quantization circuit 6. Then optimum quantization width coefficient is predicted to obtain a close object code quantity from the code quantity of the entire picture inputted from a code quantity calculation circuit 14 and the object code quantity being a maximum data quantity allowed for one picture prior to the start of the 2nd path. Thus, the code quantity is made close to the object code quantity and best picture quality is obtained. COPYRIGHT: (C)1992,JPO&Japio

Coding device and coding method for picture data

Vorrichtung und verfahren zur codierung von bilddaten, sowie hiermit ausgestattete elektronische stehbildkamera

PURPOSE: To attain encoding with high accuracy with suppressing the degradation of picture quality by executing the predictive control of quantization width based on frequency distribution status by reducing the quantization width in a picture of which high frequency components are many, based on the frequency distribution of the picture. CONSTITUTION: An evaluation signal generator 36 evaluates the magnitude of a high frequency component in a picture signal and an evaluated value is given to a quantization width predicting circuit 52 within an encoding circuit 12 and is used for quantization width setting. Besides, the evaluated value of the evaluation signal generator 36 uses the value of the half-value width of the curve of autocorrelation found by a correlation arithmetic circuit 32. Then, proper code quantity control is executed by reducing quantization width when an evaluated value E is large and by setting the quantization width large when the E is small. Thus, the optimum quantization width can be found quickly and the degradation of picture quality can be suppressed. COPYRIGHT: (C)1992,JPO&Japio

Hidetoshi Yamada

Papers

Image data coding apparatus and coding method

Image data coding apparatus and method capable of controlling amount of codes

Coding device and coding method for picture data

Vorrichtung und verfahren zur codierung von bilddaten, sowie hiermit ausgestattete elektronische stehbildkamera

Electronic camera device and encoding device for picture data