Reconstruction cohérente de l'entrée d'un banc de filtres suréchantillonnés à partir de sa sortie bruitée

International audienceIn this paper we introduce a reconstruction approach for the input signal of an oversampled filter bank (OFB) when the subbands generated at its output are quantized and transmitted over a noisy channel. We exploit the redundancy introduced by the OFB and the bounded quantization noise in order to construct a consistent estimator that corrects transmission errors. A maximum-likelihood estimation of the quantization indexes transmitted over the channel is evaluated, which only considers the vectors of quantization indexes corresponding to subband signals that could have been generated by the OFB and that are compliant with the quantization errors. Neither hypothesis tests nor specific parameters need to be set or computed in advance as is the case in approaches presented in \cite{Redinbo00,LabeauChiang2004}. When considering an OFB with oversampling ratio $3/2$, a BPSK modulation of the quantized subbands and a transmission over an AWGN channel, compared to a classical decoder, the gain is about $8$ dB in terms of reconstructed signal SNR for a channel SNR of $7$ dB

Joint source-channel coding/decoding of 3D-ESCOT bitstreams

International audienceJoint source-channel decoding (JSCD) exploits residual redundancy in compressed bitstreams to improve the robustness to transmission errors of multimedia coding schemes. This paper proposes an architecture to introduce some additional side information in compressed streams to help JSCD. This architecture exploits a reference decoder already present or introduced at the encoder side. An application to the robust decoding of 3D-ESCOT encoded bitstreams generated within the Vidwav video coder is presented. The layered bitstream generated by this encoder allows SNR scalability, and moreover, when processed by a JSCD, provides increased robustness to transmission errors compared with a single layered bitstream

Consistent Reconstruction of the Input of an Oversampled Filter Bank From Noisy Subbands

This paper introduces a reconstruction approach for the input signal of an oversampled filter bank (OFB) when the sub-bands generated at its output are quantized and transmitted over a noisy channel. This approach exploits the redundancy introduced by the OFB and the fact that the quantization noise is bounded. A maximum-likelihood estimate of the input signal is evaluated, which only considers the vectors of quantization indexes corresponding to subband signals that could have been generated by the OFB and that are compliant with the quantization errors. When considering an OFB with an oversampling ratio of 3/2 and a transmission of quantized subbands on an AWGN channel, compared to a classical decoder, the performance gains are up to 9 dB in terms of SNR for the reconstructed signal, and 3 dB in terms of channel SNR.Comment: European Signal Processing Conference (2011

MAP estimation of the input of an oversampled filter bank from noisy subbands by belief propagation

International audienceOversampled filter banks perform simultaneously subband decomposition and redundancy introduction. This redundancy has been shown to be useful to combat channel impairments, when the subbands are transmitted over a wireless channel, as well as quantization noise. This paper describes an implementation of the maximum \emph{a posteriori} and the minimum mean-square error (MMSE) estimators of the input signal from the noisy quantized subbands obtained at the output of some transmission channel. The relations between the input samples and the noisy subband samples are described using a factor graph. Belief propagation is then applied to get the posterior marginals of the input samples. The experimental results show that when the channel is clear, a linear MMSE estimate is satisfying. But, the proposed approaches perform significantly better than a reconstruction using the linear MMSE estimator when the channel is noisy: a gain in terms of channel SNR of more than $2$~dB is observed

ROBUST DECODING OF A 3D-ESCOT BITSTREAM TRANSMITTED OVER A NOISY CHANNEL

International audienceIn this paper, we propose a joint source-channel (JSC) decoding scheme for 3D ESCOT-based video coders, such as Vidwav. The embedded bitstream generated by such coders is very sensitive to transmission errors unavoidable on wireless channels. The proposed JSC decoder employs the residual redundancy left in the bitstream by the source coder combined with bit reliability information provided by the channel or channel decoder to correct transmission errors. When considering an AWGN channel, the performance gains are in average 4 dB in terms of PSNR of the reconstructed frames, and 0.7 dB in terms of channel SNR. When considering individual frames, the obtained gain is up to 15 dB in PSNR

Evaluation of Multicasting Schemes based on Joint Multiple Description and Network Coding

International audienceThis paper considers a multicast scenario and compares the average reception quality obtained when combining multiple description coding (MDC) and network coding (NC). Plain (single description) network coding (NC-SDC) serves as reference. In the considered scenario, a single source is multicast to several receivers with various channel conditions. Contrary to a NC-SDC scheme, unable to recover the coded packets when not enough combinations of packets have been received, NC of MDC packets allows a more progressive quality improvement with the number of received packets, and a reduction of the effect of the quantization noise when MDC is performed via frame expansion before quantization. Considering a probability distribution for the bit transition probability during transmission to any user in the multicast group, the expected signal-to-noise ratio is evaluated. Performance comparisons are made for various error distributions, field sizes, and MDC methods (via frame expansion and correlating transform)

Pathogenesis of Junonia coenia densovirus in Spodoptera frugiperda: A route of infection that leads to hypoxia

AbstractTo evaluate densovirus potential against lepidopteran pests and their capacity to invade new hosts, we have characterised in vivo the infection and pathogenesis of the Junonia coenia densovirus (JcDNV) in the noctuid pest Spodoptera frugiperda. Here we show that infection starts with the ingestion of viral particles that cross the midgut epithelium without replicating. By quantitative PCR we established the kinetic and the route of infection, from virus ingestion to replication in visceral tracheae and hemocytes. JcDNV has a high particle-to-infection ratio mostly due to the barrier function of the midgut. Pathology and cytopathology suggested that infection of tracheal cells impairs oxygen delivery to demanding tissues leading to cytopathic effects in all the tissues. Finally, larval death results from several physiological shocks, including molting arrest and anoxia

A review guide in public health based on the content online of the National Board Examination of Optometry

This review guide in public health follows the content outline of the public health and clinicolegal sections of part II of the NBEO examination. As such it will be of value to students preparing for National Board exams

Stroke care in Brazil and France : national policies and healthcare indicators comparison

Objective: To identify the commonalities and discrepancies between national health policies to combat stroke in France and Brazil. Justification: Both healthcare systems were structured as universal access and comprehensive care attention, hierarchized by the level of care, politically and administratively decentralized. France is an industrialized, high-income country, with health care involving copayment and reimbursement of expenses, and spontaneous demand for services. Brazil is a member of the BRICs, of upper middle income with totally free health care, with an active search for hypertension and diabetes in the general population. Methods: Data regarding policies, risk factors, and health indicators about stroke care, from 2010 to 2017, were obtained from both countries (publicly accessible information or on request) from the respective Ministries of Health or international agencies. Results: About acute stroke hospitalizations, on average, Brazil has 0.75 per 1000 annual population hospitalizations versus 1.54 per 1000 in France. Brazil has 0.21 per 1000 population deaths per year versus 0.40 per 1000 in France. The in-hospital mortality rate in Brazil has 139 per 1000 hospitalized people versus 263 in France. The average length of stay of acute hospitalizations was 7.6 days in Brazil versus 12.6 in France. The prevalence of strokes by age group shows from 0 to 39 years old (this rate is stable); 40–59 years (it is increasing in both countries); and 60–79 and 80+ years (this rate has been increasing in France and decreasing in Brazil). Conclusion: No major differences were found about the health policies and the National Health Plans related to stroke. However, the data directly linked to the period of hospitalization differed substantially between countries. Subsequent studies can be implemented to identify the explanatory factors, notably among the risk factors and actions in primary care, and the moments after hospital care, such as secondary prevention and palliative care