Intermode Decision with Varied Computational Complexity Variable block size motion compensation significantly improves the ratedistortion performance of video coding at the cost of high computational complexity. Currently, fast intermode decision algorithms only improve the speed of intermode decision (MD) but do not provide a flexible computational complexity control to adapt to different hardware platforms with optimized ratedistortion (RD) performance. Instead of speeding up intermode decision merely, we attempt to propose a complexity adjustable intermode decision algorithm to attain optimized coding performance under different computational complexity constraints herein. Our algorithm predicts the Lagrangian cost and complexity slope (JC slope) of MD for each macroblock (MB) by exploiting their temporal and spatial correlations. MD is applied on the MBs with larger JC slope to provide the better prediction performance with less computational cost. Adjustable complexity is obtained by preset the number of MBs on which MD is applied for each frame. According to our experiments, the algorithm can both freely adjust the computational complexity and provides an improved RD performance under different computational constraints.

A fast inter mode decision algorithm in H.264AVC for IPTV broadcasting services The new video coding standard H.264AVC employs the ratedistortion optimization (RDO) method for choosing the best coding mode. However, since it increases the encoder complexity tremendously, it is not suitable for realtime applications, such as IPTV broadcasting services. Therefore we need a fast mode decision algorithm to reduce its encoding time. In this paper, we propose a fast mode decision algorithm considering quantization parameter (QP) because we have noticed that the frequency of best modes depends on QP. In order to consider these characteristics, we use the coded block pattern (CBP) that has 0 value when all quantized discrete cosine transform (DCT) coefficients are zero. We also use both the early SKIP mode and early 16x16 mode decisions. Experimental results show that the proposed algorithm reduces the encoding time by 74.6% for the baseline profile and 72.8% for the main profile, compared to the H.264AVC reference software.