DCT-domain coder for digital video applications

Recent home networking services such as next generation game consoles, video-on-demand, HDTV, etc. require faster video encoders and transcoders that avoid over-complicated transformations. In most popular digital video coding standards such as MPEG-X or H.26x, discrete cosine transform (DCT), inverse DCT (IDCT) transform, and block matching algorithms are essential elements in the coding process. The transforms between the pixel and DCT domains, are taking place during the operations and being only intermediate calculations, which complicate the encoding process. Thus, it is advantageous to reduce the number of transform operations between the spatial and frequency domains in order to simplify the overall encoder structure. In this paper we propose a DCT domain video encoder for reducing processing time. This is achieved by excluding the intermediate DCT and IDCT transforms from the conventional hybrid encoder. This is achieved by calculating the motion estimation and motion compensation via a spatial relationship between the DCT coefficients of a specific block and its sub-blocks. Experimental results of this method were compared to those of the conventional hybrid video encoder in the sense of visual quality and computational complexity. The comparison shows that the computational complexity of the proposed encoder is lower by 12.5% in comparison to conventional hybrid video coder for the same visual quality.