Prediction of zero quantized DCT coefficients in H.264/AVC using Hadamard transformed information

This paper presents an efficient approach for detecting zero quantized discrete cosine transform (ZQDCT) coefficients using the sum of absolute transformed difference (SATD). Previously, all the ZQDCT prediction approaches employ the sum of absolute difference (SAD) available ahead of DCT and quantization (Q) for early detection. However, when the Hadamard transform is enabled for H.264/AVC encoding, only the SATD instead of SAD is available before DCT and Q, and all the prediction approaches can not be directly applied. To solve this problem, the Gaussian distribution is applied to study the integer 4 x 4 DCT coefficients in H.264/AVC and hence an adaptive scheme with multiple thresholds against SATD is derived to realize different types of DCT and Q implementations. In addition, another two SATD based sufficient conditions are proposed for early detecting zero quantized DC coefficients for the luma components encoded with the intra16 x 16 mode and the chroma components. The experimental results demonstrate that the proposed approach can greatly reduce the DCT and Q computations and obtain almost the same rate-distortion performance as the original encoder.