Vol.7 No.3 September 6, 2011
Research Articles
The Value of Relative Quality in Video Delivery
(0151-162)
Vlado
Menkovski, Georgios Exarchakos, and Antonio Liotta
Estimating perceived quality of video
is typically done by gauging the user’s response on an absolute scale of
ratings (excellent, good, fair, poor and bad). However, the internal
representation of these adjectives to the stimuli varies significantly
in different people. Even though the goal is to make an absolute
estimate of the perceived quality, these questions reveal merely
relative tendencies due the incorporated bias and variability in the
responses. We present results from quality assessment based on estimates
of relative quality distances between samples, by asking the question in
the form or comparison rather than rating. This, two-alternative forced
choice method scales the differences in a form of psychometric function,
which presents the utility of the perceived quality on a measurable
objective value. We argue that this relativistic mapping with low
variance is more useful in video delivery because it offers an accurate
way to optimize the resources.
A Method for Distance Estimation Using Intra-frame Optical Flow with an
Interlace Camera
(0163-176)
Tsutomu Terada,
Yuhki Suzuki, and Masahiko Tsukamoto
Recently, there are many researches on location estimation using optical
flow, which is a well-known distance estimation method without any
infrastructure. However, since the calculation of optical flow needs
high computational power, it cannot adapt to high-speed movement.
Therefore, in this paper, we propose {\em intra-frame optical flow},
which is a new distance estimation method using an interlace camera. It
can estimate the high speed moving objects accurately because it uses
two successive images with a very short scanning interval extracted from
one image captured by an interlace camera. The evaluation result
confirmed the effectiveness of our method.
Adaptive Broadband Wideo Streaming for IPTV Wireless Access
(177-193)
Salah S. Majeed
and Martin Fleury
Broadband wireless access supports mobile
applications, which may soon extend to Internet Protocol TV (IPTV). IPTV
streaming from a localized server is likely to be across a wired path
through a metro network before crossing the wireless link. In this
scenario, the paper proposes Broadband Video Streaming (BVS), which
enhances UDP transport with a single, negatively acknowledged, lost
packet retransmission. Taking IEEE 802.16e access as an example, results
demonstrate that BVS is sufficiently able to compensate for packet
losses without overly increasing delay and without the overhead of
application forward error correction, whereas unembellished UDP, and two
alternative congestion controllers (single- and multi-connection
versions of TCP-Friendly Rate Control (TFRC)) are unable to both reduce
packet loss and streaming delay. The paper exposes asymmetrical
streaming behavior between downlink and uplink streaming and finds that,
for downlink streaming, packet reordering by video picture-type packet
is sensible. The paper then extends the classic BVS scheme with an
adaptive scheme that takes into account whether packet losses are from
congestion or wireless channel conditions or a mixture of both. To cope
with this adaptive BVS adopts differentiated lost packet retransmission
according to the picture type of a lost packet. It is found that for
greater packet loss, adaptive BVS achieves equivalent objective video
quality to BVS but with reduced delay and bandwidth consumption
Realization of 3D Virtual World Platform for the Basic Education of
Adult Illiterates
(194-215)
Tassawar Iqbal,
Klaus Hammermüller, and A. Min Tjoa
Illiteracy is a dilemma, around more than 700
million adults in the world are illiterate. Along with the traditional
approaches, technology has been used for last three decades for literacy
programs. These techno-literacy solutions exploited two-dimensional (2D)
spaces with multimodal interfaces to augment learning for illiterates.
These multimodal interfaces offer audio and visual features, recommended
in learning theories. However many other features such as self-presence,
social-presence, situated-learning, embodied environment etc suggested
in these learning theories are yet to be included in these
techno-literacy solutions to further their learning. In present era,
emerging three-dimensional (3D) Virtual Worlds (VW) have potential to
provide these lacking features and many others. These 3D VWs have
already proved their importance in other disciplines such as higher
education and business; however never been investigated for Adult Basic
Education (ABE). In this paper, we explore how the benefits of 3D
emergent technologies like Second Life (SL) are exploited in coherence
with traditional theories for ABE. We present an immersive learning
platform based on Multiple Intelligences (MI) Theory. We design and
discuss an adaptive learning scenario for ABE in the SL. Finally we
scrutinize the proposed platform to get an overview of the strengths and
weaknesses in the intended area of application.
Resilient Video Stream Switching for Mobile Wireless Channels
(216-235)
Mohammad Altaf,
Martin Fleury, and Mohammad Ghanbari
In this paper, several error-resiliency
techniques are combined with the H.264/AVC (Advanced Video Coding)
codec’s switching frames to adaptively switch between video streams,
depending on wireless channel conditions. Switching frames are a feature
of H.264/AVC that allows smooth transitions between streams without the
overhead of periodic intra-coded I-frames. Because video streaming over
bandwidth-limited mobile networks requires higher compression ratios,
when ‘lossy’ channel conditions occur it is advisable to provide error
resiliency at the application layer in order to avoid degradation of
video quality at the receiver. In the scheme introduced in this paper,
when a change in channel conditions occurs, protection to the video
stream is provided by switching to an alternative stream with error
resiliency protection. To accomplish stream switching to an
error-resilient video stream, minimal feedback is necessary. In this
way, robust streaming is confined to periods of poor channel quality,
which results in up to 3-4 dB increase in video quality (PSNR) compared
to using a single robust scheme over the entire session irrespective of
channel conditions. In particular, this scheme appears suited to
conditions of slow fading, caused by changes in the environment as a
mobile device user moves from one location to another. In the paper, the
response of different error resiliency techniques to error patterns
(isolated or ‘bursty’) is determined in order to adapt in a suitable way
to channel conditions. Constant Bit Rate switching frames are also
implemented in this paper. Compared to the usual Variable Bit Rate
switching frames, CBR frames allow low-latency and low-bandwidth video
services to be supported by H.264/AVC switching frames. The robust
switching stream scheme can be potentially combined with adaptive stream
bitrate switching. However, the main gain at low bitrates comes not from
the reduced overhead of embedded switching frames but the increase in
error robustness.
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