Date of this Version
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfilment of requirements for the degree of Master of Science
Major: Electrical Engineering
Under the supervision of Professor Khalid Sayood
Lincoln, Nebraska, December 2023
A new lossless video compression technique, Match, is investigated. Match uses the similarity between the frames of a video or the slices of medical images to find a prediction for the current pixel. A portion of the previous frame is searched to find a matching context, which is the pixels surrounding the current pixel, within some distance centered on the current location. The best distance to use for each dataset is found experimentally. The matching context refers to the neighborhood of w, nw, n, and ne, where the pixel in the previous frame with the closest matching context becomes the prediction. w, nw, n, and ne stand for west, northwest, north, and northeast respectively. Using these directions, w is the pixel to the left of the current one, nw is the pixel to the left and up one row, n is the pixel directly above the current one and ne refers to the pixel up one row and to the right one column. From the prediction, the error is then calculated, remapped and encoded using adaptive arithmetic encoding. Match's resulting compression ratio is then compared to that of CALIC's, where the larger the compression ratio the more efficient the method. CALIC is a context-bases adaptive lossless image compression technique that is regarded as one of the best lossless image compression techniques. Match was evaluated for twenty-two video datasets of varying resolutions as well as 65 C.T. scans and 17 M.R.I. scans. Some common differences amongst videos are resolution and frame rate. Therefore, Match was used to compress four videos with varying resolution to see how Match is affected by resolution and Match was examined on one dataset that had varying frame rate. There were times when Match outperformed CALIC; however, there were also times where CALIC outperformed Match and other times where the two methods resulted in nearly identical compression ratios. Therefore, as a preprocessing step, the structural similarity was examined as well as the edge quality measurements to predict which method, Match or CALIC, results in the best compression.
Advisor: Khalid Sayood