Recursive Temporal Filtering and Frame Rate Reduction for Image Coding

The effect of temporal recursive filtering and frame rate reduction on a sequence of moving images is investigated. Following a well-known first-order Markov model for the temporal domain data, the effect of filtering and frame rate reduction on the values of variance, correlation coefficient, filtering distortion, and interframe prediction error are mathematically derived. The validity of these derivations is verified by the experimental results using a CCITT standard sequence which closely follows the first-order Markov model. The effect of temporal filtering and frame rate reduction to the coding rate is examined by encoding the CCITT standard sequence using a combined interframe and intraframe Scene Adaptive Coding system. At a frame rate of 30 frames per second, a 2:1 reduction in coding rate is obtained with a filtering coefficient of 0.5. At a frame rate of 10 frames per second, an additional reduction factor of nearly 2 is obtained using the same filtering coefficient. Selected images are presented to demonstrate the subjective effect.