JMM Abstracts 

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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