The bit rate for a given level of perceptual distortion is minimized.
An alternative approach has been devised for encoding image data in compliance with JPEG 2000, the most recent still-image data- compression standard of the Joint Photographic Experts Group. Heretofore, JPEG 2000 encoding has been implemented by several related schemes classified as rate-based distortion-minimization encoding. In each of these schemes, the end user specifies a desired bit rate and the encoding algorithm strives to attain that rate while minimizing a mean squared error (MSE). While rate-based distortion minimization is appropriate for transmitting data over a limited-bandwidth channel, it is not the best approach for applications in which the perceptual quality of reconstructed images is a major consideration. A better approach for such applications is the present alternative one, denoted perceptual distortion control, in which the encoding algorithm strives to compress data to the lowest bit rate that yields at least a specified level of perceptual image quality.
In tier-2 coding, the results of those coding passes for each coding block that have not been discarded are organized into an output compressed bit stream. With a carefully optimized implementation of a discrete wavelength transform, the embedded block coding tends to dominate the whole encoding time; consequently, prior JPEG 2000 encoding algorithms waste computational power and memory on those coding passes that are eventually discarded. This concludes the background information.