Subjective quality of video sequences rendered on LCD with local backlight dimming at different lighting conditions

Abstract

This paper focuses on the inuence of ambient light on the perceived quality of videos displayed on Liquid Crystal Display (LCD) with local backlight dimming. A subjective test assessing the quality of videos with two backlight dimming methods and three lighting conditions, i.e. no light, low light level (5 lux) and higher light level (60 lux) was organized to collect subjective data. Results show that participants prefer the method exploiting local dimming possibilities to the conventional full backlight but that this preference varies depending on the ambient light level. The clear preference for one method at the low light conditions decreases at the high ambient light, conrming that the ambient light signicantly attenuates the perception of the leakage defect (light leaking through dark pixels). Results are also highly dependent on the content of the sequence, which can modulate the eect of the ambient light from having an important inuence on the quality grades to no inuence at all.

Modeling the Quality of Videos Displayed With Local Dimming Backlight at Different Peak White and Ambient Light Levels

“…The influence of ambient light and peak white over the perception of images can be approached in two different ways: by the performance for a specific task [14], [15] or by studying the observer preference [6], [7], [16]. This paper focuses on the latter aspect.…”

“…In [6], Guterman et al report little effect of both ambient light and peak white on the observer preference. However a significant interaction of the ambient light is noted in [7] with the LBD method. Moreover, in [16] the authors show that observers' preference increases with higher peak white for High Dynamic Range (HDR) images when two contents are displayed side by side.…”

“…This was done in [7] where the authors tried two pre-processing methods: adding the reflected luminance to the image luminance and using the function developed in [15]. The latter function from [15] provided promising results.…”

“…The data collected through those two different tests are presented and analyzed in this paper. In the first test, the independent factors were the source sequence (Sequence), the backlight dimming method (Method) and the Ambient light [7]. In the second test an additional factor was added: the Peak white of the screen (i.e.…”

“…Both are part of the general viewing conditions and impact the visual perception [5], [6]. In regard to LBD, they are both tightly linked to the leakage artifact [7], [8]. Indeed as the leakage practically results in an increase of the minimum black level, the perception of it is highly influenced by the amount of light that is reflected by the display and by the luminance adaptation level of the observer's eye.…”