Quantization of 3D-DCT Coefficients and Scan Order for Video Compression

This paper proposes a technique for generating the quantization values for 3D-DCT coefficients. The distribution of AC coefficients inside a transform cube is characterized by two regions, theshifted complement hyperboloidand theshifted hyperboloid,which capture the dominant and the less significant coefficients, respectively. An exponential function is used to determine the appropriate quantization values for the two regions. A quantization volume for the 3D-DCT is generated by using the function. The paper also describes a novel procedure for deriving the scan order for the quantized 3D-DCT coefficients. The proposed quantization volume has been tested on various standard test video sequences. The experiments show that the 3D-DCT video compression using the proposed quantization values produce high compression ratios with good visual quality for the reconstructed video frames. If desired, the parameter settings of the function can be further tuned for better visual quality. The proposed scan order was also found to be superior, in terms of compression ratio, to the 3D zig zag approach, which is an extension of the traditional 2D zig zag.