Information Technology Reference
In-Depth Information
1 Introduction
Networked three-dimensional (3D) media services are becoming increasingly fea-
sible through the evolution of digital media, entertainment, and visual communica-
tion. Three-dimensional television (3DTV), one of the popular media services, can
provide a dramatic enhancement in user experience, compared with the traditional
black-and-white and color television. Although David Brewster introduced the
stereoscope, a device that could take photographic pictures in 3D, in 1844, it was
not until 1980s that experimental 3DTV was presented to a large audience in
Europe. However, although various recent technological developments combined
with an enhanced understanding of 3D perception have been achieved, many im-
portant topics related to 3D technology are almost unexplored [1]. A networked
3DTV service consists of an entire chain from content production and coding
schemes for transmitting through communication channels to adequate displays
presenting high quality 3D pictures. During this chain, the quality of a 3D presen-
tation may be degraded at each stage. In this chapter, we will focus on perceptual
quality assessment of visual experience for stereoscopic images. Human factors as
well as typical artefacts in 3D presentations that may affect the quality of visual
experience will be reviewed, and we will mainly focus on coding and transmission
artefacts. To study the relationship between perceived quality and distortion
parameters for stereoscopic images, a subjective quality assessment has been con-
ducted. Furthermore, accurate metrics which can predict stereoscopic image qual-
ity will be proposed based on two-dimensional (2D) image quality metrics and
disparity information.
Before going to the detailed discussions on quality assessment at each stage in
the chain, understanding the human factors that can affect the quality of visual ex-
perience is necessary. The relationship among some psycho-visual factors, such as
sensation of depth, perceived sharpness, subjective image quality, and relative
preference for stereoscopic over non-stereoscopic images, was investigated in [2].
The main finding is that viewers usually prefer a stereoscopic version rather than a
non-stereoscopic version of image sequences, given that the image sequences do
not contain noticeable stereo distortions, such as exaggerated disparity. Perceived
depth is rated greater for stereoscopic sequences than that for non-stereoscopic
ones, whereas perceived sharpness of stereoscopic sequences is rated same or
lower compared to non-stereoscopic sequences. Subjective rating on stereoscopic
image quality is influenced primarily by apparent sharpness of image sequences,
whereas the influence of perceived depth is not evident. As early as in 1993, tech-
nological requirements for comfortable viewing in 3D display were studied [3]. To
reduce visible image distortion and visual strain, a basic requirement (image size),
visual noise requirements (disparity range, disparity resolution), and motion paral-
lax (viewpoint sampling, brightness constancy, registration tolerance, and perspec-
tive interpolation) are required. Stelmach et al. [4] found that the sensation of
depth, image quality and sharpness are affected differently by different spatial
resolutions and temporally filtering schemes. The overall sensation of depth is not
affected by low-pass filtering, and larger spatial resolutions usually make more
contribution to the rating of quality and sharpness. Field averaging and
Search WWH ::




Custom Search