Scan order and quantization for 3D-DCT coding

Two types of coders dominate the field of video compression research today: well-established hybrid coders, that are in the core of all MPEG and H.26X standards, and emerging three-dimensional (3D) subband coders, largely inspired by the success of wavelet-based still image compression. However, there are surprisingly few results reported on 3D transform coding based on the discrete cosine transform (DCT). Even while exploiting all the beneficial properties of the DCT itself (forward/inverse symmetry, fast separable implementation, and excellent energy compaction), these coders under-perform when compared to competing hybrid coders primarily due to inefficient quantization, scanning and entropy coding used. In this paper, we study means of improving 3D-DCT coding by proposing adaptive scanning order and quantization of coefficients that are better matched to 3DDCT spectrum of a motion sequence. Our results show significant improvement in performance over previously reported techniques.