System and method for generating decoded digital video image data

Abstract

Methods and systems are disclosed for decoding image data including I-picture, P-picture, and B-picture encoded data. A method includes receiving encoded image data and selectively performing a modified inverse discrete cosine transform (IDCT) process to generate output pixel array blocks at a lower resolution than the resolution of the received image data. The image data can be 8×8 pixel array blocks, which are used to produce lower resolution pixel array blocks such as, for example, 4×8 or 4×4 pixel array blocks. In certain instances, after the IDCT process is performed, the resulting pixel data is up-sampled before motion compensation is performed. Furthermore, in certain instances, the resulting pixel data is subjected to motion compensation and scaled to display size prior to display.

1 - 25 . (canceled) 
     
     
         26 . A method for displaying an image on a portion of a display having a lower resolution than the rest of the display, the method performed by a processor, and the method comprising:
 receiving encoded image data comprising I-picture, P-picture, and B-picture data;   performing inverse discrete cosine transform (IDCT) decoding on I-picture and P-picture data at a first resolution and on B-picture data at a second resolution, the second resolution being lower than the first resolution;   performing motion compensation processing on the decoded P-picture and B-picture data;   scaling the decoded and motion-compensated image data based on the size of the portion of the display; and   displaying the scaled image data on the lower resolution portion of the display.   
     
     
         27 . The method as recited in  claim 26 , wherein the first resolution comprises full vertical resolution and one-half horizontal resolution. 
     
     
         28 . The method as recited in  claim 26 , wherein the second resolution comprises one-half vertical resolution and one-half horizontal resolution. 
     
     
         29 . The method as recited in  claim 26 , wherein performing motion compensation processing comprises:
 obtaining motion vector data;   determining if the motion vector data specifies a pixel position that does not have a corresponding pixel within the picture data;   if the motion vector data has a missing pixel, up-sampling the picture data from its scaled resolution to compute a replacement pixel; and   down-sampling the picture data with the replacement pixel to its scaled resolution.   
     
     
         30 . A method for displaying an image on a portion of a display having a lower resolution than the rest of the display, the method comprising:
 receiving an array of discrete cosine transform (“DCT”) coefficients representing a block of image data of one of a plurality of types of pictures;   performing IDCT on a sub-portion of the DCT coefficients to obtain a block of pixel data equal in size to the sub-portion if the block of image data represents a first type of picture;   performing motion compensation on the block of pixel data to obtain a second block of pixel data;   scaling the second block of pixel data based on a size of the portion of the display; and   displaying the scaled pixel data on the portion of the display.   
     
     
         31 . The method of  claim 30 , wherein the first type of picture includes a bi-directionally predictive-coded picture. 
     
     
         32 . The method of  claim 30 , wherein the array of DCT coefficients is 8×8 in size and the sub-portion of the DCT coefficients is 4×8 in size. 
     
     
         33 . The method of  claim 30 , wherein the array of DCT coefficients is 8×8 in size and the sub-portion of the DCT coefficients is 4×4 in size. 
     
     
         34 . A method for decoding image data, the method performed by a processor, and comprising:
 receiving encoded image data comprising I-picture, P-picture, and B-picture data;   performing IDCT decoding on I-picture data at a first resolution;   scaling the decoded I-picture data based on a display size, and outputting the scaled I-picture data for display;   performing IDCT decoding on P-picture data at the first resolution;   performing motion compensation processing on the decoded P-picture data;   scaling the motion-compensated P-picture data based on the display size, and outputting the scaled P-picture data for display;   performing IDCT decoding on B-picture data at a second resolution, the second resolution being lower than the first resolution;   performing motion compensation processing on the decoded B-picture data; and   scaling the motion-compensated B-picture data to the display size; and   outputting the scaled B-picture data for display.   
     
     
         35 . A method for decoding image data performed by a processor, the method comprising:
 receiving encoded image data comprising I-picture, P-picture, and B-picture data;   performing IDCT decoding on I-picture and P-picture data at a first resolution and on B-picture data at a second resolution, the second resolution being lower than the first resolution;   performing motion compensation processing on the decoded P-picture and B-picture data;   scaling the decoded and motion-compensated image data based on a display size; and   outputting the scaled image data for display.