Adaptive Method for Early Detecting Zero Quantized DCT Coefficients in H.264/AVC Video Encoding

In H.264/AVC video encoding, zero quantized discrete cosine transform (DCT) coefficients are quite common in low bit-rate video application. The computations of DCT and quantization can be remarkably reduced if zero quantized DCT coefficients are detected prior to DCT and quantization. Many methods have been applied to early detect most zero quantized DCT coefficients. But the detection ratios of zero quantized DCT coefficients need to be improved when quantization parameter (QP) is small. We present an adaptive method to detect zero quantized DCT coefficients. When QP exceeds a certain value, a new threshold is derived to efficiently detect the all-zero blocks (AZBs) without any video degradation. Otherwise, a concept of fourteen-zeros block (FZB), which means only two coefficients are non-zero in 16 DCT coefficients of a 4 times 4 block, is proposed. An innovative method to process FZBs is proposed to reduce the redundant computations. Experimental results show that the proposed adaptive method achieves approximately 8%-20% computational savings, compared with that of the existing methods.