This paper presents a Learning System (LS) which offers Greek Sign Language videos in correspondence to every text in the learning environment. The system is designed notably for deaf adults for the purpose of their lifelong vocational and educational training. In the LS, the special needs of Deaf learners are satisfied, e.g. bilingual information (text and sign language), high level of visualization, interactive and explorative learning, and the potential of learning in peer groups via video conferencing. In this environment, for the first time, Greek signers are able to learn in their own language, the sign language. In addressing the above context, the LS is adapted to the specific learning problems of the target group, i.e. deaf adolescents and young adults. The provided content is bilingual. Bilingual experiments (spoken and signed language) in schools of the deaf and hearing impaired have shown that the use of sign language in the classroom enhance reading competence significantly. The basic objective of the present e-learning environment is the support of the equal rights of Deaf people for their access and real attendance in the vocational and educational training. The development of LS and this paper has been supported by Leonardo Da Vinci Framework Program, "DELFE" project, of European Union.
We propose methods for selecting the modelling parameters of H.263-quantized video traffic under two different encoding scenarios. For videos encoded with a constant quantization step (unconstrained), we conclude that a two-parameter power relation holds between the exhibited video bit rate and the quantizer value and that the autocorrelation decay rate remains constant for all cases. On the basis of these results, we propose a generic method for estimating the modelling parameters of unconstrained traffic by means of measuring the statistics of the single "raw" video trace. For rate-controlled video (constrained), we propose an approximate method based on the adjustment of the "shape" parameter of the counterpart-with respect to rate-unconstrained video trace. The convergence of the constructed models is assessed via q-q plots and queuing simulations. On the assumption that the popular MPEG-4 encoders like XVID, DIVX usually employ identical H.263 quantization and rate control schemes, it is expected that the results of this paper also hold for the MPEG-4 part 2 family.
is paper presents modelling results for H.26x video traffic generated by popular videoconference soware applications. e analysis of videoconference data, that were measured during realistic point-point videoconference sessions, led us to the general conclusion that the traffic can be distinguished into two categories: unconstrained and constrained. In the unconstrained traffic, there is a direct relation between the encoder and the form of the frequency histogram of the frame-size sequence. Moreover, for this type of traffic, strong correlations between successive video frames can be found. On the other hand, where bandwidth constraints are imposed during the encoding process, the generated traffic appears to exhibit similar characteristics for all the examined encoders with the very low autocorrelation values being the most notable one. On the basis of these results, this study proposes methods to calculate the parameters of a widely adopted autoregressive model for both types of traffic.
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