Fast algorithms for newest H.264 video coding standard

Abstract

Variable Block Size (VBS) is one of the newest techniques proposed in H.264 video coding standard for inter frame motion estimation. The main reason for using VBS, ranging from 4x4 to 16x16, is to represent the motion more accurately. In VBS, seven block sizes that include 16x16, 16x8, 8x16, 8x8, 8x4, 4x8, and 4x4 are tried before the best one is selected from RD optimization (RDO). The best selection after all trials is optimal in terms of bit rate reduction and quality preservation. However, this feature results in computational complexity and consuming time especially when the brute force full-search algorithm is employed. In order to improve computation time, “Progressive Inter Mode Selection Algorithm” (PIMSA) is proposed in this report for selecting some candidate inter block based on stationarity property. Stationarity refers to the “stillness” between adjacent frames temporally such as background and non-moving objects. Computation can be save by better estimation of stillness blocks possess such stationarity property. In additional, two innovative methods are included in PIMSA. The first one is one-bit transform for improving selection accuracy by removing redundancy information. The second one is “Inter Block Mode Predictor” (IBMP) for selecting possible blocks modes and attempting to predict direct mode.