Objective image quality measure for block-based DCT coding

Abstract

The block-based discrete cosine transform (DCT) coding has been widely adopted in image or video compression standards, such as R E G and MPEG. Such type of coding will produce a noticeable artifalct known as the blocking effect at very low bit rate applications. In the literature, there have been various postprocessing methods proposed to reduce the blocking effect. However, there is no suitable objective criterion evaluating the effectiveness of these various methods. This paper presents a new objective measure evaluating the postprocessing methods. The proposed measure also provides an analytical result on the underlying sources of artifacts.

No-reference image-quality metric based on blur radius and visual blockiness

“…In the proposed method, the blur radius was estimated from edge blocks in a reblurred image while the global radius estimation method 26 used two reblurred versions. The proposed blocking metric was also designed to take into account diagonal blockiness visibility as well as horizontal and vertical blockiness, while the existing blocking metrics [10][11][12]14,15 considered only horizontal and vertical directions. Sections 2 and 3 describe the proposed blur and blocking metrics.…”

“…[10][11][12][13][14][15][16][17] In these methods, the amount of blockiness has been estimated by taking into account the characteristics of each compression standard ͑e.g., MPEG, JPEG͒ in the spatial and frequency domains. For instance, certain blocking artifacts have been detected and evaluated using the weighted difference along block boundaries.…”

“…For instance, certain blocking artifacts have been detected and evaluated using the weighted difference along block boundaries. [10][11][12] They have also been measured by the power of the blocky signal, the visibility, and activity in the DCT domain. 13 This has been done by modeling two-dimensional step functions in the shifted blocks and calculating the blocking visibility and activity.…”