Recently, the popularity and utility of video transmission
over bandwidth constrained, error-prone networks has
increased dramatically. This is due to the growing demand for
various multimedia applications. It is therefore important
to develop an error-resilient, low-complexity video coder
that is capable of achieving a desired quality of service (QoS).
The objectives of this study are the following :
1. Improve the performance of a low-complexity, gracefully degrading error-resilient entropy coder (FEREC). Methods to exploit the unequal error protection property of FEREC and other error protection codes to protect against packet loss for transmission over heterogeneous networks will be explored.
2. New adaptive rate control algorithms based on low-complexity, on-line stochastic optimization algorithms that improve the QoS will be studied. Experiments to compute the optimal parameter values of the rate controller such as the quantization step size, adaptation rate etc.
3. Perform various software-based experiments that study the error-resilience of layered coding based on MPEG, H.263 and the wavelet transform. Initial results can be found here
In this project, an empirically optimized channel-matched quantizer, and
a joint rate controller and channel
estimator for a H.261 based video
encoder is proposed. The theory and
experimentation behind the empirical optimization of the
channel matched quantizer is discussed.
The rate controller adaptively chooses the optimal
channel matched quantizer using a stochastic learning
automaton. The automaton learns the channel characteristics based
on a one bit feedback from the decoder.
The rate control algorithm is shown to converge
to the optimal choice of the quantizer very quickly for various
channel bit error probabilities and for different video sequences.
The peak signal to noise
ratio of the received video signal is seen to improve using
the proposed approach. The proposed method reduces the delay and
bandwidth incurred in using pilot symbol aided channel estimation
and transmission techniques.
