SUBJECTIVE QUALITY ASSESSMENT OF SCALABLE VIDEO CODING: A SURVEY
Jong-Seok Lee, Francesca De Simone, Touradj Ebrahimi
Multimedia Signal Processing Group (MMSPG)
Ecole Polytechnique F´ ed´ erale de Lausanne (EPFL)
CH-1015 Lausanne, Switzerland
{jong-seok.lee, francesca.desimone, touradj.ebrahimi}@epfl.ch
ABSTRACT
Scalable video coding is a promising solution for efficient
video content distribution to users having heterogeneous net-
work and terminal capabilities. Thanks to its inherent multi-
dimensional adaptability, a scalable bit stream can be used to
simultaneously transmit multiple video sequences having dif-
ferent bit rates to corresponding target users, without neces-
sity of re-encoding or transcoding. In order to exploit such an
advantage effectively, it is crucial to understand the effects of
multidimensional scalability options on the perceived quality
and the trade-off between the scalability dimensions through
subjective quality assessment. This paper reviews existing
studies aiming at achieving this goal in order to summarize
their results and common findings.
Index Terms— Scalable video coding, subjective quality
assessment, quality of experience
1. INTRODUCTION
Nowadays, applications of video content delivery are very
popular thanks to the advances of hardware and software tech-
nologies for video production and processing. Usually, a con-
tent, e.g. a video clip on a video sharing web site, is consumed
by many users. This brings an important research issue: how
to efficiently deliver video content to consumers having di-
verse communication environments. Network resources (e.g.
bandwidth) available for different users may be quite different
and time-varying. In addition, the characteristics of users’ ter-
minals may vary significantly in terms of display resolution,
processing power, etc. Therefore, the same content needs to
be delivered at the same time in different formats according
to these variables.
Scalable video coding is a useful concept that can deal
with such difficulty in multimedia content delivery. A scal-
The research leading to these results has received funding from the Euro-
pean Communitys Seventh Framework Programme (FP7/2007-2011) under
grant agreement no. 216444 (PetaMedia), the Swiss National Foundation
for Scientific Research in the framework of the NCCR Interactive Multi-
modal Information Management (IM2), and the COST Action IC1003 Euro-
pean Network on Quality of Experience in Multimedia Systems and Services
(Qualinet).
Fig. 1. Three-dimensional video scalability.
able video bit stream is composed of various layers, which
can be adapted to a given bit rate constraint through trunca-
tion of parts of the bit stream. In general, the video scalability
is realized in the following three dimensions (Fig. 1):
• Spatial scalability, i.e. possibility of reducing the frame
size;
• Temporal scalability, i.e. possibility of reducing the
frame rate;
• Signal-to-noise ratio (SNR) scalability (or quality scal-
ability), i.e. possibility of reducing the frame quality.
Having the three different scalability dimensions, video
transmission using scalable video coding schemes requires
an adaptive strategy to determine which scalability options
to be used for given resource constraints. When a bit rate
limitation is given, the three dimensions have trade-off rela-
tionship, e.g. increasing the spatial resolution can be done
only at the cost of the decreased temporal resolution and/or
frame quality. The ultimate goal of such a strategy is to max-
imize end-users’ quality of experience for the delivered con-
tent. Therefore, it is important to understand the impact of
different scalability options and their combinations on human
2011 Third International Workshop on Quality of Multimedia Experience
978-1-4577-1335-4/11/$26.00 ©2011 IEEE 25