Fast PCRD-Opt computation in JPEG2000

In this paper, an integer-based post-compression rate-distortion optimization (PCRD-Opt) algorithm for JPEG2000 rate control is presented. The distortion estimation described in the JPEG2000 standard requires non-integer processing, and the overwhelming computational burden on JPEG2000 is the distortion calculation, which is calculated for every bit of the uncompressed image. In this paper, an integer-based approach for distortion calculation is proposed. The proposed method reduces the computational requirements for PCRD-Opt within the Tier I encoder, as well as provides a more straightforward algorithm for embedded processing, requiring no distortion look-up tables (LUTs) for proper distortion computation. The proposed integer-based method improves upon the PCRD-Opt method described in the standard. Specifically, the proposed method reduces the Tier-I processing time from an offline implementation of PDRD-Opt utilizing LUTs by approximately 18% on average, and reduces the overall JPEG2000 processing by 15%. The proposed integer-based distortion estimation provides an equivalent rate-distortion (RD) curve as both the offline PCRD method described in the standard.