Encoding Of Subband Images Using Adaptive Vector DPCM
K. S. Thyagarajan, Hasan Gadjali, Sanjiv Bhatt · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1988
This paper describes an adaptive vector differential pulse code modulation (VDPCM) for the encoding of subband images. These subband images are obtained by splitting an image into subbands, using quadrature mirror filter (QMF) banks, followed by a 2:1 decimation. Linear phase FIR filters are used for the QMF filter bank. In this work, only one level of splitting, four bands partition, is performed. The subband images are encoded using adaptive VDPCM to a achieve bit rate of 0.5 bit per pixel. Each of the subband images is divided into small blocks of size M by M, at the encoder, and K-dimensional vectors are formed from subblocks of k by 1. Linear block prediction is then performed along the rows and the prediction error is quantized using a matrix quantizer within the VDPCM loop. As the energy distribution among the subband images is not even each of the subbands are encoded at different rates. Since the low low (LP LP) band has the highest energy and carries all the essential details of the original image in a compressed form, it is encoded at a higher rate as compared to the other bands.