Enhanced Quality Scalability for JPEG2000 Code-Streams by the Characterization of the Rate-Distortion Slope

Quality scalability is a fundamental feature of JPEG2000, achieved through the use of quality layers. Two points, related with the use of quality layers, may need to be addressed when dealing with JPEG-2000 code-streams: 1) the lack of quality scalability of single quality layer code-streams, and 2) the non rate-distortion optimality of windows of interest transmission. This paper introduces a new rate control method that can be applied to already encoded code-streams, addressing these two points. Its main key-feature is a novel characterization that can fairly estimate the rate-distortion slope of the coding passes of code-blocks without using any measure based on the original image or related with the encoding process. Experimental results suggest that the proposed method is able to supply quality scalability to already encoded code-streams achieving a near-optimal coding performance. The low computational costs of the method makes it suitable for use in interactive transmissions.