Context-Based Rate Distortion Estimation and Its Application to Wavelet Image Coding

Embedded image coding in wavelet domain has drawn a lot of attention. Among noteworthy algorithms is the embedded block coding with optimized truncation (EBCOT) algorithm, which has been adopted by the JPEG2000 standard. EBCOT is a two-tier algorithm. Tier-1 is composed of bit-plane coding followed by entropy coding. Tier-2 performs the so-called post compression rate distortion optimization (PCRD), which requires a large memory space for storing all the code streams of code blocks; however, some code blocks of less importance might not be needed for the optimal decoded image at a bit rate. To avoid waste of computational power and memory space, a simple context based rate distortion estimation (CBRDE) is thus proposed to arrange the scanning order of code blocks in an adaptive manner. The CBRDE algorithm is based on the MQ table of JPEG2000, which is available at both encoder and decoder. As a result, there is no need to store and transmit the rate distortion information of code blocks. Experimental results show that the rate distortion curves are almost convex; this demonstrates the potential of CBRDE for embedded wavelet image coding. Key-Words: embedded image coding; wavelet transform; JPEG2000; EBCOT; PCRD; CBRDE The National Science Council of Taiwan, under Grant 97-2221-E-239-031-MY2 supported this work.