Optimal Bit Allocation in Subband Loop Coding for Multimedia Processing ANDREJA SAMCOVIC, ZORAN BOJKOVIC, DRAGORAD MILOVANOVIC Faculty of Traffic and Transport Engineering University of Belgrade Vojvode Stepe 305 YUGOSLAVIA Abstract: - Subband signal decomposition has been successfully applied to multimedia applications. Closed-loop coding, where quantization noise feedback at the encoder is included, and open-loop coding are investigated. Closed-loop coding has several advantages. The Gaussian rate-distortion models are presented, and analytical solutions of the optimal bit allocation problem are derived. Key-Words: - Subband coding, signal decomposition, loop coding, multimedia, bit allocation, compression, rate-distortion 1 Introduction The goal of classical signal compression is to achieve the highest possible compression ratio. The compression and transmission aspects have generally been treated as separable issues. The first problem with this approach is that the resulting compression algorithms usually do not address the needs of networked transmission. The second difficulty in separately designing the compression and transmission components is caused by the fact that a successful compression algorithm removes all the redundancy and hence the compressed data must be delivered error free. The challenge of multimedia processing is to provide services that integrate text, sound, image and video information. To achieve this goal, there are a number of technological problems that must be considered, including compression, coding and transmission of miltimedia signals. During the last decade, subband coding (SBC) has become a popular method for signal compression. A broad range of schemes for coding of the subband signals have been proposed. Often, bit allocation is performed among the subbands, and even within the subbands, to maximize the coding gain and exploit variations in the local image statistics. There are various methods for bit allocation. Two of the most popular algorithms, producing an overall fixed rate, were proposed by Shoham and Gersho [1] and Westerink et al [2]. These “equal-slope”