Efficient rate control for JPEG2000 image coding
JPEG2000 is the new image coding standard which can provide superior rate-distortion performance over the old JPEG standard. However, the conventional post-compression rate-distortion (PCRD) optimization scheme in JPEG2000 is not efficient. It requires entropy encoding all available data even though a large portion of them will not be included in the final output. In this paper, three rate control methods are proposed to efficiently reduce both the computational complexity and memory usage over the conventional PCRD method. The first method, called successive bit-plane rate allocation (SBRA), allocates the bit rate by using the currently available rate-distortion information only. The second method, called priority scanning rate allocation (PSRA), allocates bits according to certain prioritized ordering. The third method uses PSRA to achieve optimal truncation as PCRD without encoding of all the image details and is called priority scanning with optimal truncation (PSOT). Simulation results suggest that the three proposed methods provide different tradeoff among visual quality, computational complexity, coding delay and working memory size. SBRA is memoryless and causal and requires the least computational complexity, lowest coding delay and achieves good visual quality. PSRA achieves higher PSNR than SBRA at the expense of larger working memory size and longer coding delay. PSOT gives the best PSNR but requires even more computation, delay and memory.