3 research outputs found
Dynamic adaptation of streamed real-time E-learning videos over the internet
Even though the e-learning is becoming increasingly popular in the academic environment,
the quality of synchronous e-learning video is still substandard and significant work needs to be
done to improve it. The improvements have to be brought about taking into considerations both:
the network requirements and the psycho- physical aspects of the human visual system.
One of the problems of the synchronous e-learning video is that the head-and-shoulder video
of the instructor is mostly transmitted. This video presentation can be made more interesting by
transmitting shots from different angles and zooms. Unfortunately, the transmission of such
multi-shot videos will increase packet delay, jitter and other artifacts caused by frequent
changes of the scenes. To some extent these problems may be reduced by controlled reduction
of the quality of video so as to minimise uncontrolled corruption of the stream. Hence, there is a
need for controlled streaming of a multi-shot e-learning video in response to the changing
availability of the bandwidth, while utilising the available bandwidth to the maximum.
The quality of transmitted video can be improved by removing the redundant background
data and utilising the available bandwidth for sending high-resolution foreground information.
While a number of schemes exist to identify and remove the background from the foreground,
very few studies exist on the identification and separation of the two based on the understanding
of the human visual system. Research has been carried out to define foreground and background
in the context of e-learning video on the basis of human psychology. The results have been
utilised to propose methods for improving the transmission of e-learning videos.
In order to transmit the video sequence efficiently this research proposes the use of Feed-
Forward Controllers that dynamically characterise the ongoing scene and adjust the streaming
of video based on the availability of the bandwidth. In order to satisfy a number of receivers
connected by varied bandwidth links in a heterogeneous environment, the use of Multi-Layer
Feed-Forward Controller has been researched. This controller dynamically characterises the
complexity (number of Macroblocks per frame) of the ongoing video sequence and combines it
with the knowledge of availability of the bandwidth to various receivers to divide the video
sequence into layers in an optimal way before transmitting it into network.
The Single-layer Feed-Forward Controller inputs the complexity (Spatial Information and
Temporal Information) of the on-going video sequence along with the availability of bandwidth
to a receiver and adjusts the resolution and frame rate of individual scenes to transmit the
sequence optimised to give the most acceptable perceptual quality within the bandwidth
constraints.
The performance of the Feed-Forward Controllers have been evaluated under simulated
conditions and have been found to effectively regulate the streaming of real-time e-learning
videos in order to provide perceptually improved video quality within the constraints of the
available bandwidth
Quality-oriented adaptation scheme for multimedia streaming in local broadband multi-service IP networks
The research reported in this thesis proposes, designs and tests the Quality-Oriented Adaptation Scheme (QOAS), an application-level adaptive scheme that offers high quality
multimedia services to home residences and business premises via local broadband IP-networks in the presence of other traffic of different types. QOAS uses a novel client-located grading scheme that maps some network-related parametersā values, variations and variation patterns (e.g. delay, jitter, loss rate) to application-level scores that describe the quality of delivery. This grading scheme
also involves an objective metric that estimates the end-user perceived quality, increasing its effectiveness. A server-located arbiter takes content and rate adaptation decisions based on these quality scores, which is the only information sent via feedback by the clients.
QOAS has been modelled, implemented and tested through simulations and an instantiation of it has been realized in a prototype system. The performance was assessed in terms of estimated end-user perceived quality, network utilisation, loss rate and number of customers served by a fixed infrastructure. The influence of variations in the parameters used by QOAS and of the networkrelated
characteristics was studied. The schemeās adaptive reaction was tested with background traffic of different type, size and variation patterns and in the presence of concurrent multimedia streaming processes subject to user-interactions. The results show that the performance of QOAS
was very close to that of an ideal adaptive scheme. In comparison with other adaptive schemes QOAS allows for a significant increase in the number of simultaneous users while maintaining a good end-user perceived quality. These results are verified by a set of subjective tests that have been performed on viewers using a prototype system
Efficient Passive Clustering and Gateways selection MANETs
Passive clustering does not employ control packets to collect topological information in ad hoc networks. In our proposal, we avoid making frequent changes in cluster architecture due to repeated election and re-election of cluster heads and gateways. Our primary objective has been to make Passive Clustering more practical by employing optimal number of gateways and reduce the number of rebroadcast packets