Modeling of 3-D DCT coefficients for fast video encoding

The discrete cosine transform (DCT) plays a key role in image/video coding due to its powerful energy concentration ability. On the other hand, since many DCT coefficients will be quantized to zeros, a huge number of redundant computations are introduced. This paper proposes an analytical model to predict the zero-quantized DCT (ZQDCT) coefficients for fast 3- D DCT based video encoding. The theoretical analysis is first performed to study the sufficient condition under which each DCT coefficient becomes zero. Then, the threshold for each ZQDCT coefficient is mathematically determined. Finally the transform and quantization operations of the predicted ZQDCT coefficients are omitted. We show, by the experimental results, that the proposed model can significantly reduce the redundant computations and achieve better real-time performance than the original encoder without any quality degradation. Computational reduction also implies longer battery lifetime and energy economy for digital applications.