We propose a source-rate control scheme for streaming video over a wireless channel. The scheme is designed to maximize the quality of the decoded video as perceived at the user-side by resorting on a reduced-reference video-quality estimation approach. The advantage is that the measured video quality, which drives the rate-control algorithm, is obtained after channel errors and error concealment. The rate control algorithm works adjusting the rate on a per-window basis to compensate low-throughput periods with high-throughput periods so as to avoid the “saw” effect that is typically observed in frame-based rate control.

A simple image scrambling method for image-based authentication (IBA) is proposed and evaluated. The devised scheme may be embedded into any wavelet-based IBA framework to provide mutual authentication with challenge-response architecture. The severe constraints on security, data transmission capability and user friendliness are addressed by the complete system, especially in the wireless environment. Data and application scalability is provided through the JPEG2000 standard and JPIP framework

A novel framework for image-based authentication (IBA) is proposed and evaluated. The proposed system relies on data and application scalability in order to optimize its performance in several environments, from wired applications to mobile authentication. Data scalability is exploited through the JPEG2000 standard and JPIP framework. The wireless environment, in particular, imposes severe constraints on data transmission capability and user friendliness, which are satisfied by the devised system

Transmission errors in JPEG2000 can be grouped into three main classes, depending on the affected area: LL, high frequencies at the lower decomposition levels, and high frequencies at the higher decomposition levels. The first type of errors are the most annoying but can be concealed exploiting the signal spatial correlation like in a number of techniques proposed in the past; the second are less annoying but more difficult to address; the latter are often imperceptible. In this paper, we address the problem of concealing the second class or errors when high bit-planes are damaged by proposing a new approach based on the theory of projections onto convex sets. Accordingly, the error effects are masked by iteratively applying two procedures: low-pass (LP) filtering in the spatial domain and restoration of the uncorrupted wavelet coefficients in the transform domain. It has been observed that a uniform LP filtering brought to some undesired side effects that negatively compensated the advantages. This problem has been overcome by applying an adaptive solution, which exploits an edge map to choose the optimal filter mask size. Simulation results demonstrated the efficiency of the proposed approach.

A new coding scheme for lossy to lossless compression of volumetric data using a three-dimensional packet wavelet transform is presented. The need of a unitary transform via the integer lifting scheme and the performance comparison of different integer filter kernels is discussed. A state-of-the-art coder, set partitioning in hierarchical trees (SPIHT), is considered and modified in order to adapt its tree-structure to the 3D packet wavelet structure defined. The algorithm is extensively tested and shows very good performance, both for lossy and lossless coding.

In this paper, we address the problem of concealing high-frequencies errors at the lower decomposition levels in JPEG2000, by proposing a new approach based on the theory of projections onto convex sets. The error effects are masked by iteratively applying two important procedures: low-pass (LP) filtering in the spatial domain and restoration of the uncorrupted wavelet coefficients in the transform domain. It has been observed that a uniform LP filtering brought to some undesired side-effects that negatively compensated the advantages. This problem has been overcome by applying an adaptive solution exploiting an edge map to choose the optimal filter mask dimension. Simulation results demonstrated the efficiency of the proposed approach.