To decode encoded video using a computer with a central processing unit and a graphics processing unit as a coprocessor, parameters applied to blocks of intermediate image data are transferred from the central processing unit to the graphics processing unit. When the operation being performed applies to a small portion of the blocks of intermediate image data, then the central processing unit can transfer to the graphics processing unit the parameters for only those blocks to which the operation applies. In particular, the central processing unit can transfer a set of parameters for a limited number of blocks of intermediate image data, with an indication of the block to which each set of parameters applies, which both can improve speed of operation and can reduce power consumption.