An original blurriness assessment method for video frames is presented. In the first place two measurements
are performed uniformly on the whole frame. The first quantifies the perceptive contrast experienced by the
human eye, the second uses anisotropic diffusion to estimate a possible detail loss due to blurriness. Secondarily
two further indices are devised, each one suitable to a particular sort of image content. The first is dedicated
to main, uniform objects, where smoothed borders are deemed to be the main source of blurriness perception.
First, a technique is devised to extract all edges, including the smoothest ones. Then the width of such edges
is measured, and more weight is given to long than to short ones. The second index measures the activity of
textured areas, trying to detect blurriness inside the base texture elements. The four devised indices enable
automatic quantification of the strength of blurriness and some hints at its origin. In particular, some new
results have been achieved in the ability to automatically distinguish natural blurriness, present in the image
content, from undesired one, introduced during encoding and processing.
A method is presented to measure the intensity of the blocking artefact in compressed pictures or video frames.
First, a way is devised to artificially introduce pure blocking, which closely resembles the real one subsequent
to JPEG compression. Then a modified no-reference measurement is proposed that requires less computations
than other formerly presented methods, permits to take into account the whole image or frame area, and is
not affected by interlaced video. Some first experiments indicate that the measured values relate closely to the
introduced blockiness effect. The robustness of the metric to the influence of other typical JPEG artefacts is
also checked. Further, the effect on blockiness of some enhancement strategies is measured. Pictures enhanced
with methods introducing the most severe blockiness are found to have the highest value of the proposed metric.
Finally the problem of blockiness measurement in video sequences is addressed. In this case the blocking grid is
no longer regular. In fact, blocks of different size could be used in encoding, and single blocks could be shifted
in referenced (P and B) frames due to motion compensation. A method is devised for grid detection.