All-Zero Blocks Detection And Its Applications In H.264/AVC Video Encoding

H.264/AVC is the latest video encoding standard established by JVT between ITU-T VCEG and ISO/IEC MPEG. It has a significant performance benefit comparing with older standards in compression performance. However, it also has a considerable increase in encoder complexity, which limits the application it can be used for. Therefore, reducing the computations of the encoder is vital for this standard.Three efficient algorithms for early detect AZBs (all-zero blocks) are proposed, which is on the basis of theoretical analyzes for the integer DCT (discrete cosine transform) and quantization in H.264/AVC. The process of DCT, quantization, inverse quantization and IDCT (inverse discrete cosine transform) can be omitted and large computations can be reduced if AZBs are detected early. Morever, all-zero blocks detection is used in prediction.mode decision and motion estimation to greatly reduce the computational complexity of H.264/AVC encoding. The main results are as follows:Based on the current methods, a more presise threshold which can be used to detect more AZBs with fewer overheads is deduced for H.264/AVC encoding. And an enhanced 3-step AZBs detection method is proposed in order to computing the threshold everytime. The experimental results show that the proposed algorithm can early detect plenty of AZBs and omit consideralble DCT and quantization operations without any video quality degration.By studying the properties of DCT coefficient distribution in lots of test video sequences, a fast algorithm for all-zero bocks detection is proposed in the paper. This algortithm cost little ovevheads and greatly improve the AZBs detection ratio with negligible video quality degradation.A general Gaussian distribution based model is applied to study the residual coefficients and DCT coefficients in H.264/AVC encoding. And a hybrid algorithm for all-zero block detection is proposed. The experimental results show that the proposed algorithm can early detect four kinds of 4 X 4 blocks including AZBs and reduce large redundant computations required in the process of DCT and quantization with receivable video quality.A fast mode decision algorithm is proposed for H.264/AVC encoding, which is on the basis of the application of all-zero blocks detection. By skipping some prediction mode after some comparions, the algorithm can greatly reduce the computations when RDO (Rate-Distortion Optimization) is used.A fast motion estimation algorithm based on the application of all-zero blocks detection is proposed for H.264/AVC encoding, in which a distortion preventive is adopted to keep search veracity. The experimental results show that the proposed algorithm can speed up the motion estimation search. In a word, all-zero detection and its applications provide some new methods for H.264/AVC encoding optimization.