CDP Trancoding Indian Institute of Technology KharagpurCDP转码克勒格布尔印度科技学院.pptVIP

Image Transcoding in the block DCT Space Jayanta Mukhopadhyay Department of Computer Science Engineering Indian Institute of Technology, Kharagpur, 721302, India jay@cse.iitkgp.ernet.in 2-D DWT 1D DWT applied to vertical and horizontal direction. For Multilevel DWT:- The LL band is recursively decomposed, vertically and horizontally. Filtering is performed in time domain. DCT domain Upsampling with Zero Insertion A typical conversion matrix4x4 block to 8x8 upsampled type-II DCT Computation of upsampled DCT Wavelet synthesis in the DCT domain Result is transcoded type-II DCT coefficients. Operation is equivalent to IDWT + DCT. Transcoding in the DCT domain Wavelet to DCT Transcoding (WDT) WDT computes DCT blocks of larger size. By decomposing, 8x8 blocks are obtained. Cost of transcoding increases. To reduce the cost, smaller blocks are to be considered. WBDT: * Three blocks of NxN size are used in a wavelet subband of size WxW. * Blocks are Upsampled, composed, filtered and decomposed. * The transcoded blocks of size 2Nx2N. Note:- N=4 for JPEG based applications. WBDT computes DCT blocks of size 8x8, Uses composing and decomposing of DCT blocks. Requires Type-I DCT of filter and Type-II DCT of data. Linear Filtering in the DCT domain: Requires only Type-II DCT. Blocks are processed separately and added together. The WBDTL, * Three adjacent NxN size subband blocks are used. * Upsampled blocks filtered separately and the results are added. * Computes the transcoded blocks of size 2Nx2N. Note:- For JPEG based applications, N=4. Transcoding with Multilevel DWT JPEG2000 9/7 wavelet filters Analysis Filters Synthesis Filters Wavelet filters and responses Wavelet filters and responses Results Results: Quantization of wavelet subbands Observations The proposed new algorithms for transcoding the DCT coefficients from wavelet coefficients are computationally efficient. Both the approaches (WBDT and WBTL) are found to