Statistically cycle optimized bounding box for high definition video decoding
A method for conserving memory accesses in motion compensation of compressed video gathers a plurality of motion compensation data accesses into a single bounding box for direct memory access data transfer. The method places the motion compensation data of a current macroblock into a current bounding box until placing the motion compensation data into the current bounding box causes the ratio of motion compensation data to bounding box data to fall below a predetermined memory utilization threshold.
1. A method for motion compensation of compressed video comprising the steps of for each macroblock in a video frame:
updating the coordinates of a bounding box encompassing a plurality of macroblocks assuming the current macroblock is to be included in the current bounding box;
calculating the area of the current bounding box as expanded to encompass the current macroblock;
determining if the area of the current bounding box exceeds a maximum bounding box area;
if the area of the current bounding box exceeds a maximum bounding box area, closing the current bounding box with dimensions before said updating coordinates and opening a new bounding box encompassing the current macroblock;
calculating a bounding box memory utilization by a ratio of motion compensation data to bounding box data;
if the bounding box memory utilization is less than a predetermined memory utilization threshold, closing the current bounding box with dimensions before said updating coordinates and opening a new bounding box encompassing the current macroblock; and
upon consideration of a plurality of macroblocks for a portion of a video frame, transferring motion compensation data for the plurality of macroblocks via direct memory access data transfer of the bounding boxes.
2. The method of claim 1 , further comprising the steps of:
performing the method on a digital signal processor having a data cache of a predetermined size; and
selecting said maximum bounding box area corresponding to said predetermined size of said data cache.
3. The method of claim 1 , further comprising the steps of:
before said step of updating the coordinates of the bounding box
comparing a current macroblock count assuming the current macroblock is to be included in the current bounding box to a maximum macroblock count, and
if the current macroblock count is greater than the maximum macroblock count, closing the current bounding box with dimensions before said updating coordinates and opening a new bounding box encompassing the current macroblock.