A guaranteed-rate tiled memory-data compression

Abstract

A method of compressing digital image data is provided that includes, for each image data block in a plurality of image data blocks in the digital image data, transforming image data in the image data block to convert the image data to a low-frequency coefficient and a plurality of high-frequency coefficients, computing a predicted low-frequency coefficient for the image data block based on at least one neighboring image data block in the plurality of image data blocks, computing a residual low-frequency coefficient based on the predicted low-frequency coefficient and the low-frequency coefficient, quantizing the plurality of high-frequency coefficients, and entropy coding the residual low-frequency coefficient and the quantized high-frequency coefficients.

What is claimed is: 
     
         1 . A method of compressing digital image data, the method comprising:
 for each image data block in a plurality of image data blocks in the digital image data,
 transforming image data in the image data block to convert the image data to a low-frequency coefficient and a plurality of high-frequency coefficients; 
 computing a predicted low-frequency coefficient for the image data block based on at least one neighboring image data block in the plurality of image data blocks; 
 computing a residual low-frequency coefficient based on the predicted low-frequency coefficient and the low-frequency coefficient; 
 quantizing the plurality of high-frequency coefficients; and 
 entropy coding the residual low-frequency coefficient and the quantized high-frequency coefficients. 
   
     
     
         2 . The method of  claim 1 , further comprising:
 selecting a quantization parameter and an entropy coding parameter using rate control, wherein the rate control guarantees a predetermined compression rate.   
     
     
         3 . The method of  claim 2 , wherein the rate control allocates an extra initial bit-rate to an initial image data block and gradually reduces the extra initial bit-rate for subsequent image data blocks to guarantee the predetermined compression rate. 
     
     
         4 . The method of  claim 1 , wherein transforming image data comprises:
 performing a two-dimensional integer wavelet transform on the image data block, wherein a sufficient number of lifting steps are performed to convert the image data into the low-frequency coefficient and the plurality of high-frequency coefficients.   
     
     
         5 . The method of  claim 1 , wherein computing a predicted low-frequency coefficient comprises computing the predicted low-frequency coefficient based on a left neighboring image data block, a top neighboring image data block, and a top-left neighboring image data block. 
     
     
         6 . The method of  claim 1 , wherein the digital image data is a reference frame. 
     
     
         7 . A system for compressing digital image data, the system comprising:
 a transform component configured to transform image data in an image data block of a plurality of image data blocks in the digital image data to convert the image data to a low-frequency coefficient and a plurality of high-frequency coefficients;   a prediction component configured to determine a predicted low-frequency coefficient for the image data block based on at least one neighboring image data block in the digital image data;   a combiner configured to subtract the predicted low-frequency coefficient from the low-frequency coefficient to generate a residual low-frequency coefficient;   a quantizer configured to quantize the plurality of high-frequency coefficients; and   an entropy coding component configured to entropy code the residual low-frequency coefficient and the quantized high-frequency coefficients.   
     
     
         8 . The system of  claim 7 , further comprising:
 a rate control component configured to determine a quantization parameter for the image data block wherein a predetermined compression rate is guaranteed; and   a parameter selection component configured to interact with the rate control component to select a quantization parameter and an entropy coding parameter for the image data block.   
     
     
         9 . The system of  claim 8 , wherein the rate control component allocates an extra initial bit-rate to an initial image data block and gradually reduces the extra initial bit-rate for subsequent image data blocks to guarantee the predetermined compression rate. 
     
     
         10 . The system of  claim 7 , wherein the transform component is configured to perform a two-dimensional integer wavelet transform on the image data block, wherein a sufficient number of lifting steps are performed to convert the image data into the low-frequency coefficient and the plurality of high-frequency coefficients. 
     
     
         11 . The system of  claim 7 , wherein the prediction component is configured to determine the predicted low-frequency transform coefficient based on a left neighboring image data block, a top neighboring image data block, and a top-left neighboring image data block. 
     
     
         12 . The system of  claim 7 , wherein the digital image data is a reference frame.