This paper investigates the performance and proposes modifications to earlier methods for image authentication
using distributed source coding. This approach works well on images that have undergone affine geometric
transformations such as rotation and resizing and intensity transformations such as contrast and brightness
adjustment. The results show that the improvements proposed here can be used to make the original scheme for
image authentication robust to affine geometric and intensity transformations. The modifications are of much
lesser computational complexity when compared with other schemes for estimation of channel parameters.
In contrast to conventional video coding, Wyner-Ziv video coders
perform simple intra-frame encoding and complex inter-frame decoding using
side information. An important process in Wyner-Ziv decoding
is the reconstruction process. So far, two main reconstructions have
been used: the Maximum a Posteriori (MAP) reconstruction and the Minimum
Mean Square Error (MMSE) reconstruction. In this paper, we study the
MAP and MMSE reconstructions for both Pixel-Domain and Transform-Domain
Wyner-Ziv video coders.
We also present a new reconstruction function for Pixel-Domain Wyner-Ziv video coders
that adapts to the local accuracy of the side information.
Experimental results show that our adaptive reconstruction provides
improvements over both the MAP and the MMSE reconstructions.
Wyner-Ziv video coders perform simple intra-frame encoding and complex inter-frame decoding. This feature makes this type of coder suitable for applications that require low-complexity encoders. Video coding algorithms provide coding modes and parameters so that encoders can fulfill rate constraints and improve the coding
efficiency. However, in most Wyner-Ziv video coders, no algorithm is used to optimally choose the coding modes and parameters. In this paper, we present a rate control algorithm for pixel-domain Wyner-Ziv video coders. Our algorithm predicts the rate and distortion of each video frame as a function of the coding mode and the quantization parameter. In this way, our algorithm can properly select the best mode and quantization for each video frame. We show experimentally that, even though the rate and distortion cannot be accurately predicted in Wyner-Ziv video encoders, rate constraints are approximately fulfilled and good coding efficiency is obtained
by using our algorithm.