Gian Antonio Mian

Lossless compression of video using temporal information

In this paper, we consider the problem of lossless compression of video by taking into account temporal information. Video lossless compression is an interesting possibility in the line of production and contribution. We propose a compression technique which is based on motion compensation, optimal three-dimensional (3-D) linear prediction and context based Golomb-Rice entropy coding. The proposed technique is compared with 3-D extensions of the JPEG-LS standard for still image compression. A compression gain of about 0.8 bit/pel with respect to static JPEG-LS, applied on a frame-by-frame basis, is achievable at a reasonable computational complexity.

Accuracy analysis for correlation-based image registration algorithms

The behavior of two image registration techniques (the cross-correlation and the phase-correlation algorithms) for input signals corrupted by additive white noise is studied in the frequency domain. Useful expressions of the displacement measurement error variance are presented, which allows for the analysis of the accuracy of both methods. Both methods are more sensitive to noise for low-pass inputs (blurred images) than they are for high-pass inputs (textured, sharp images). The phase-correlation technique is more sensitive to noise than direct cross-correlation both for low-pass and high-pass inputs.<<ETX>>

Effects of quantization in second-order fixed-point digital filters with two's complement truncation quantizers

Second-order direct-form digital filters with two twos-complement truncation quantizers are analyzed. The regions of the parameter plane where limit cycles of period one and two exist are first determined, and their locations are related to the possible cycle values. The global asymptotic stability (GAS) of the filter is then investigated in the region where no such limit cycles are possible within the stability triangle of the associated linear filter. The GAS is proved for a fairly large area by an analytical procedure. The GAS area is then extended using an exact exhaustive search. >

Multistage sampling structure conversion of video signals

The work extends multistage implementation of sampling structure conversion to the multidimensional (M-D) case. The issues arising in this task are usefully addressed on the basis of lattice theory. Numerical data supporting the advantages of multistage sampling conversion are presented, and the case of format conversion from the 4/3 to the 16/9 aspect ratio is examined as a study case. The main indication of the present work is that multistage implementation, in the case of systems for sampling structure conversion of video signals, may improve the system characteristics and visual rendition. >

An H.264/AVC Video Coder Based on a Multiple Description Scalar Quantizer

Transmission of encoded video sequences over unreliable networks usually requires the adoption of protection techniques to guarantee good reconstruction quality at the receiver side. Multiple description coding (MDC) strategies add reliability to real-time video applications, where retransmission is not possible and packet losses afflict several frames degrading the overall quality. This paper presents a novel MDC scheme based on the H.264/AVC standard and a multiple description scalar quantizer which encodes the residual information into two descriptions. Finally, objective and visual performances are presented.

An Accurate Low-Complexity Rate Control Algorithm Based on

The standard H.264/AVC defines an efficient coding architecture both for coding applications where bandwidth or storage capacity is limited (e.g., video telephony or video conferencing over mobile channels and devices) and for applications that require high reconstruction quality and bit rate (e.g., HDTV). Since its main applications concern video communication over time-varying bandwidth channels, the bit rate has to be controlled with scalable algorithms that can be implemented on low resource devices. The paper describes a rate control algorithm that needs reduced memory area and complexity compared to other ones. The number of coded bits for each frame is accurately predicted through the percentage of null quantized transform coefficients, which is related to the quantization step via the energy of the quantized signal. It is possible to design a rate control algorithm based on this model that provides a good compression performance at a low computational cost.

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Granular camera noise is per se objectionable in high-quality TV and it is a source of bothersome visual artifacts with digitally coded video sequences. The first and second order statistical characteristics of this noise are investigated in this work. The results quantify intuitively expected notions, such as the relative unimportance of chrominance noise with respect to the luminance noise and the spatially colored nature of the noise. Noise reduction techniques can use, as general guidance rules, the indications of the presented analysis. >

-Domain

Examines the distinctive features of 2D diamond-shaped filters, a class of filters quite important for video interpolation/decimation. The geometrical interpretation of linear programming is proposed as an easy tool for understanding the characteristics of M-D FIR filters minimax optimal and the effects of the constraints most common in video application. The relationships between minimax error, filter orders and bandwidth of diamond-shaped FIR filters are investigated, extending results typical of 1D minimax filter design. The effect of constraining one of the filter orders to a pre-assigned value (provision quite useful if the filter order under consideration determines the number of frame-stores) is studied extensively. In light of the reported characteristics of the diamond-shaped FIR filters their multistage implementation becomes extremely attractive. The advantages and the potential of multi-stage implementation of diamond-shaped filters are discussed. >

Statistical characteristics of granular camera noise

We present some results on audio restoration obtained with an algorithm that solves the problems of broadband noise filtering, signal parameters tracking, and impulsive noise removal by using the Extended Kalman Filter (EKF) theory. We show that, to achieve maximum performance, it is essential to optimize the EKF implementation. To this purpose, having to cope with the nonstationarity of the audio signal, we use two properly combined EKF filters (forward and backward), and introduce a bootstrapping procedure for model tracking. The careful combination of the proposed techniques and an accurate choice of some critical parameters, allows to improve the performance of the EKF algorithm. The presented procedure is validated by listening tests.

Characteristics of minimax FIR filters for video interpolation/decimation

We develop an adaptive scheme for quantization of subband or transform coded frames in a typical video sequence coder. Using a generalized Gaussian model for the subband or transform coefficients, we present a procedure to determine the optimum dead-zone quantizer for a given entropy of the quantizer output symbols. We find that, at low bit rates, the dead-zone quantizer offers better performance than the uniform quantizer. The model is used to develop an adaptive procedure to update the quantizer parameters on the basis of the state of a channel buffer with constant output rate and variable input rate. We compare the accuracy of the generalized Gaussian model in predicting the actual bit rate to that achievable using the simpler and more common Laplacian model. Experimental results show that the generalized Gaussian model has superior performance than the Laplacian model, and that it can be effectively used in a practical scheme for buffer control.