Abstract: The present invention divides a video frame into a series of smaller and smaller quadrants until reaching a single pixel size. By issuing a series of commands, a logical cursor moves within the quadrants to evaluate the frame for changes from the previous frame. Upon detecting a color change, the exact location (identified by a level and a quadrant thereof) is encoded along with a value for the change. As a result of the novel approach disclosed herein, there may be significant storage savings over the prior art.

Abstract: A method for update writing in an array of DASDs in a reduced number of DASD track cycles. The method involves distributing data and parity blocks for each parity group across the array in failure independent form and reserving unused space. During a first cycle, the old data and parity blocks are read. The new parity is calculated and shadow written into reserved unused space located before the old parity block recurs. The amended data is either written in place during a second cycle or shadow written into reserved space during a subsequent portion of the first cycle.