Modelling of spatio–temporal interaction for video quality assessment

Video services have appeared in the recent years due to advances in video coding and convergence to IP networks. As these emerging services mature, the ability to deliver adequate quality to end-users becomes increasingly important. However, the transmission of digital video over error-prone and bandwidth-limited networks may produce spatial and temporal visual distortions in the decoded video. Both types of impairments affect the perceived video quality. In this paper, we examine the impact of spatio–temporal artefacts in video and especially how both types of errors interact to affect the overall perceived video quality. We show that the impact of the spatial quality on overall video quality is dependent on the temporal quality and vice-versa. We observe that the introduction of a degradation in one modality affects the quality perception in the other modality, and this change is larger for high-quality conditions than for low-quality conditions. The contribution of the spatial quality to the overall quality is found to be greater than the contribution of the temporal quality. Our results also indicate that low-motion talking-head content can be more negatively affected by temporal frame freezing artefacts than other general type of content with higher motion. Based on the results of a subjective experiment, we propose an objective model to predict overall video quality by integrating the contributions of a spatial quality and a temporal quality. The non-linear model shows a very high linear correlation with subjective data.     

Analytical Solution of Thermo-elastic Stresses and Deformation of Functionally Graded Rotating Hollow Discs with Radially Varying Thermo-mechanical Properties under Internal Pressure

Exact analytical solution for functionally graded hollow discs under internal pressure, thermal load and rotation are provided in this paper. Material properties of discs, i.e. elastic modulus, density and thermal expansion coefficient are assumed to vary in radial direction. Two power functions are assumed for property dependency to study various types of functional grading of materials in the discs. Assuming small deformations, a differential equation is obtained and solved for the Airy stress function. The effects of various grading functions on the stress and deformation distribution are studied and an optimum value for the power is obtained.     

Fuzzy logic congestion control for broadband wireless IPTV

All-IP broadband networks are being created with multimedia bandwidth requirements in mind. A unicast IPTV service forming a pipe or sub-channel on the converged network may need to negotiate a broadband wireless link. Where there is a need for multiple variable bit rate video streams to share the same pipe a problem of link utilisation arises [1], requiring congestion control at the server bank. Conventional controllers such as TCP-friendly rate control (TFRC) [2] and TCP emulation at receivers (TEAR) [3], originating in a TCP-dominated internet, will stream video up to the capacity of the pipe, but reacting to feedback may overestimate the capacity, resulting in packet loss, which leads to reduced video quality. In this Letter, fuzzy logic control (FLC) is shown to outperform conventional control in such a network by changing the quantisation parameter for live video or through a bit rate transcoder for pre-encoded video. Moreover, compared to prior use of traditional (type-1) fuzzy logic for similar purposes [4], interval type-2 (IT2) FLC has been employed, as this is robust to feedback measurement uncertainties.     

Synthesis,characterization and TL properties of SrSO_4:Dy,Tb nanocrystalline phosphor

SrSO4:Dy,Tb nanocrystalline with crystalline size in the range of 44–54 nm was prepared by co-precipitation method followed by thermal treatment and characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDX) and UV-visible spectrometry. Our results provided direct evidence of incorporation of impurities into nanocrystalline SrSO4. The thermoluminescence(TL) properties of SrSO4:Dy,Tb nanocrystalline pellets irradiated with gamma rays at different doses were studied. The TL glow curve of SrSO4:Dy,Tb nanocrystalline pellets had a prominent peak at around 490 K and a small peak at around 430 K. The major peak in the TL glow curve was almost resolved from other peaks, which was analyzed using Chen's peak shape method to determine the TL kinetic parameters such as activation energy, E and kinetic order, b. The intensity of main dosimetric peak of SrSO4:Dy,Tb nanocrystalline pellets at around 490 K increased linearly with the increase in gamma dose. The TL response was linear in the range of 0.1–7 kGy. These properties made it a candidate as a dosimeter to be used for estimating the high dose of gamma rays.     

Digital demodulation by a non-coherent differential PSK modem

A DPSK demodulator which uses a digital delay line is presented. By digitising the demodulation process, the hardware design for the receiver is simplified. This also gives a greater flexibility to demodulate different carrier frequencies and data bit rates with the same receiver. The performance of the digital demodulator is compared with the theoretical values, for a range of error rates.<>