Integer-based, post-compression rate-distortion optimization computation in JPEG2000 compression

Abstract

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 noninteger processing, and the overwhelming computational burden on JPEG2000 is the distortion calculation, which is calculated for every bit of the uncompressed image. 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 lookup 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 a direct implementation of PCRD-Opt by approximately 39% on average and reduces the overall JPEG2000 processing by 34%. The proposed method reduces the Tier I processing time from an offline implementation of PDRD-Opt utilizing LUTs by approximately 21% on average, and reduces the overall JPEG2000 processing by 19%. The proposed integer-based distortion estimation provides a rate-distortion curve equivalent to both the direct and offline PCRD methods described in the standard.