Optimized Pre-Compensating Compression

Abstract

In imaging systems, following acquisition, an image/ video is transmitted or stored and eventually presented to human observers using different and often imperfect display devices. While the resulting quality of the output image may severely be affected by the display, this degradation is usually ignored in the preceding compression. In this paper we model the sub-optimality of the display device as a known degradation operator applied on the decompressed image/video. We assume the use of a standard compression path, and augment it with a suitable pre-processing procedure, providing a compressed signal intended to compensate the degradation without any post-filtering. Our approach originates from an intricate rate-distortion problem, optimizing the modifications to the input image/video for reaching best end-to-end performance. We address this seemingly computationally intractable problem using the alternating direction method of multipliers (ADMM) approach, leading to a procedure in which a standard compression technique is iteratively applied. We demonstrate the proposed method for adjusting HEVC image/video compression to compensate post-decompression visual effects due to a common type of displays. Particularly, we use our method to reduce motion-blur perceived while viewing video on LCD devices. The experiments establish our method as a leading approach for preprocessing high bit-rate compression to counterbalance a postdecompression degradation.

Compression for Multiple Reconstructions

“…The EPLL implementation used here is with respect to a fidelity term corresponding to (2) and suitable parameter settings. The third competing method is our pre-compensating compression from [1], optimized only for a single display (corresponding to the highest probability). The implementation of the proposed method (Algorithm 1) uses aβ value based on the HEVC quality parameter (thẽ β value here is 10 times the value formulated in [1]).…”

“…We recently [1] proposed an optimization methodology to adjust standard image/video compression to a known type of display presenting the decompressed signal to the viewer. Our framework essentially pre-compensates the display degradation from the compression standpoint in a rate-distortion optimized manner.…”

“…Our framework essentially pre-compensates the display degradation from the compression standpoint in a rate-distortion optimized manner. Here we extend the problem settings of [1] to optimize the compression with respect to a set of display devices, described by several linear rendering models and their probabilities to be in use by consumers. One can interpret the display models and their usage probabilities as a characterization of a multimedia distribution network.…”

“…the displayed signal. Similar to our previous works [1], [2], we address the computationally hard optimization using the alternating direction method of multipliers (ADMM) [3] translating the task to sequentially applying standard compressions (that are network independent!) and 2 -constrained deconvolutions expressing the network structure.…”

“…We demonstrate our general approach for image compression using the state-of-the-art HEVC standard coupled with various simplified display models in the form of linear blur operators following the decompression. While another recent method [7] optimizes image rendering with respect to a perceptual quality metric, we present here (and in [1]) a method to globally optimize the flow of compression, decompression and rendering. Since our optimization goal and the distortion type differ from those in [7], the two methods cannot be quantitatively compared.…”