EE Seminar: Combating Packet Loss in Image Coding using Oversampling and Irregular Interpolation
Speaker: Mor Goren
M.Sc. student under the supervision of Prof. Ram Zamir
Wednesday, January 2th, 2018 at 15:00
Room 011, Kitot Bldg., Faculty of Engineering
Combating Packet Loss in Image Coding using Oversampling and Irregular Interpolation
Abstract
In the age of the Internet, where communication lies deeply on networks that suffer from packet loss, there is a great need in a system that can provide a reliable communication of information in presence of erasures and quantization noise (an outcome of compression). Using source channel separation principle, we suffer of cliff phenomenon, with no improvement in case the channel behaves better than the usual.
Diversity "multiple description" (MD) source coding promises graceful degradation in the presence of an unknown number of erasures in the channel. A simple solution in the case of two descriptions consists of oversampling the source by a factor of two and delta-sigma quantization. This approach was applied successfully to JPEG-based image coding over a lossy packet network, where the interpolation into two packets is done in the discrete cosine transform (DCT) domain.
The extension to a larger number of descriptions, however, suffers from noise amplification whenever the received descriptions form a nonuniform sampling pattern. Previous work shows that using frames for oversampling, irregular spectrum is the best possibility for nonuniform sampling pattern, among tested frames, in a way that it minimizes the excess rate.
In this work we show how noise amplification can be reduced by optimizing the interpolation filter. We propose two interpolation methods which, for a given total coding rate, minimize the average distortion over all (K out of N) patterns of received packets, known as side receivers in the MD literature. We provide experimental results comparing low-pass (LP) and irregular interpolation filters for the side receivers, and examine the effect of noise shaping on the trade-off between the all-N central receiver and the side receivers.
