INRIA Rennes--Bretagne-Atlantique

This paper presents a traitor tracing method dedicated to video content distribution. It is based on a probabilistic traitor tracing code and an orthogonal zero-bit informed watermark. We use the well-known Tardos fingerprinting tracing function to reduce the search space of suspicious users. Their guiltiness is then confirmed by detecting the presence of a personal watermark embedded with a personal key. To prevent watermarking key storage at the distributor side, we use a part of the user probabilistic fingerprinting sequence as a personal embedding key. This method ensures a global lower false alarm probability compared to original probabilistic codes. Indeed, we combine the false alarm probability of the code with the false alarm probability of the watermarking scheme. However the efficiency of this algorithm strongly depends on the number of colluders at the watermarking side. To increase the robustness, we present an additive correlation method based on successive watermarked images, we then study its limitation under different sizes of collusion.

A popular and effective method to protect professional content against illegal distribution is to use watermarking, which inserts a robust and imperceptible fingerprint in the data using complex information hiding techniques. Video DNA watermarking is a state-of-the-art technique which enables shifting of the computational complexity to the server side. Despite the high level of protection it provides, this technique comes at a price in terms of storage space, as several versions of the same content have to be stored on the server. It is possible to limit the impact in terms of bitrate by slightly decreasing the quality of the final video. In this paper, we evaluate the impact of using Video DNA watermarking on the perceived quality by presenting the results of a standardized subjective experiment. We study various strategies to minimize the impact on the quality while maintaining the same overall bitrate, acting on the spatial resolution of the videos and bitrate repartition schemes.

This paper presents a new decoder for probabilistic binary traitor tracing codes under the marking assumption. It is based on a binary hypothesis testing rule which integrates a collusion channel relaxation so as to obtain numerical and simple accusation functions. This decoder is blind as no estimation of the collusion channel prior to the accusation is required. Experimentations show that using the proposed decoder gives better performance than the well-known symmetric version of the Tardos decoder for common attack channels.

This paper presents a traitor tracing method dedicated to video content distribution. It is based on a two-level approach with probabilistic traitor tracing codes. Codes are concatenated and decoded successively, the first one is used to decrease the decoding complexity and the second to accuse users. We use the well-known Tardos fingerprinting code for the accusation process and a Boneh Shaw code with replication scheme to reduce the search space of users. This method ensures to reduce the computational time compared to classical Tardos codes decoding. We present different methods to select suspect groups of users and compare them to a more complex two-level Tardos code which fallows the same construction.

This paper presents a traitor tracing method dedicated to video content distribution. It is based on a probabilistic traitor tracing code and an orthogonal zero-bit informed watermark. We use the well-known Tardos fingerprinting tracing function to reduce the search space of suspicious users. Their guiltiness is then confirmed by detecting the presence of a personal watermark embedded with a personal key. To prevent watermarking key storage at the distributor side, we use a part of the user probabilistic fingerprinting sequence as a personal embedding key. This method ensures a global lower false alarm probability compared to original probabilistic codes. Indeed, we combine the false alarm probability of the code with the false alarm probability of the watermarking scheme. However the efficiency of this algorithm strongly depends on the number of colluders at the watermarking side. To increase the robustness, we present an additive correlation method based on successive watermarked images, we then study its limitation under different sizes of collusion.

This paper addresses the issue of robust transmission of Variable Length Codes (VLCs) encoded sources over error-prone channels. A new class of codes, called self-multiplexed codes, is introduced. Their performance in terms of compression is the same as the one of classical VLCs (e.g. Huffman codes). Their property in terms of energy distribution on respective transitions of the codetree allows to confine error propagation to transitions bearing low reconstruction energy. Simulation results reveal high performances in terms of signal to noise ratio.

We consider the problem of sending two correlated random sources over a Gaussian multiple-access channel. The sources are assumed to be temporally memoryless. The performance criterion is the MSE and we seek linear transceivers that minimize it. When the bandwidth expansion factor is unity, it is shown that uncoded transmission is the best linear code for any SNR. When the bandwidth expansion factor is two, we present a scheme that involves uncoded transmission of one source with appropriate power adaptation and uncoded transmission of the other source and its negative with appropriate power adaptation. This scheme is shown to strictly ourperform coding strategies based on TDMA.

We consider distributed linear transceivers for sending a secondorder wide-sense stationary process observed by two noisy sensors over a Gaussian multiple-access channel (MAC). We derive the minimum mean-square error (MSE) distributed linear transceiver. The optimal linear transmitter exploits bandwidth expansion by repeating transmission and the transmitters at the two sensors are the same except for a constant factor. When the source is white, uncoded transmission is the best linear code for any SNR. But for a colored source, whitening transmit filter is sub-optimal. In high SNR regime, the magnitude response of the optimal transmission filter is inversely proportional to fourth-root of the power spectrum of the process (while that for the whitening filter is inversely proportional to the square-root of the spectrum). In the special case of a single sensor with Gaussian source, we also quantify the performance loss of linear source-channel codes with respect to the Shannon limit.

The development of 'Beyond 3G'-B3G-or '4G' networks and applications, with all-IP based ubiquitous and seamless service provisioning across heterogeneous infrastructures, presents a number of challenges beyond existing capabilities conceived so far by the IETF for Mobile IP and by the ITU for Third Generation networks. Management, signaling and transport functions must evolve from different link layer technologies, uniformly and end-to-end, to the packet switched IP-network layer. Global mobility throughout all network types requires capability for seamless handover between different administrative and technology domains, extending at the same time the present edge mobility concept to ad-hoc networks and to mobile networks. Having at least identified, if not solved, these important problems, the technical key challenge for this B3G or '4G' world remains to provide IP-based audio and video communications at the same or at least comparable 'carrier class' and bandwidth efficiency as the corresponding circuit-switched subsystems of 3G and 2G. In the IETF, some elements to achieve this goal have been identified and are under discussion: situated between link and IP layers, the Robust Header Compression (ROHC) framework addresses the problems of spectrum and bandwidth scarcity and of bit errors characterizing wireless links. The fact that, for some applications, erroneous packet payloads can be valuable and better to cope with than lost ones, has inspired the introduction of the UDP-lite transport protocol. Assuming ROHC, UDP-lite and an appropriate inter-or cross-layer signaling mechanism in action, this paper is going to elaborate and incorporate the joint source and channel coding-JSCC-paradigm into a complete QoS framework for 4G mobile wireless multimedia communications. q

Overcomplete frame expansions have been introduced recently as signal representations resilient to erasures on packet networks such as the Internet and wireless networks. This paper is dedicated to a broad analysis of a class of frames derived from the generator matrices of DFT codes. In contrast to earlier presentations, which focused on the analysis of only low-pass DFT codes, this analysis aims at comparing the performance of all BCH codes and MDS negacyclic codes derived from the DFT codes. It is proven that all BCH codes, and MDS negacyclic codes derived from the BCH codes, are equivalent in the sense that they produce the same mean square error averaged over all erasure patterns of a given length under the same quantization error model. On the way to this result, the special property of the frames associated with the BCH codes, and the reconstruction equivalence between the frame-theoretic approach and the coding-theoretic approach, are proved in general settings. The paper also discusses optimal packetization of BCH codevectors and the performance of non-BCH codes that have the same erasure recovery capacity as BCH codes.  2004 Elsevier Inc. All rights reserved.

This paper addresses the issue of robust and progressive transmission of signals (e.g., images, video) encoded with variable length codes (VLCs) over error-prone channels. This paper first describes bitstream construction methods offering good properties in terms of error resilience and progressivity. In contrast with related algorithms described in the literature, all proposed methods have a linear complexity as the sequence length increases. The applicability of soft-input soft-output (SISO) and turbo decoding principles to resulting bitstream structures is investigated. In addition to error resilience, the amenability of the bitstream construction methods to progressive decoding is considered. The problem of code design for achieving good performance in terms of error resilience and progressive decoding with these transmission strategies is then addressed. The VLC code has to be such that the symbol energy is mainly concentrated on the first bits of the symbol representation (i.e., on the first transitions of the corresponding codetree). Simulation results reveal high performance in terms of symbol error rate (SER) and mean-square reconstruction error (MSE). These error-resilience and progressivity properties are obtained without any penalty in compression efficiency. Codes with such properties are of strong interest for the binarization of M-ary sources in state-of-the-art image, and video coding systems making use of, for example, the EBCOT or CABAC algorithms. A prior statistical analysis of the signal allows the construction of the appropriate binarization code.

This paper introduces source-channel adaptive rate control (SARC), a new congestion control algorithm for layered video transmission in large multicast groups. In order to solve the well-known feedback implosion problem in large multicast groups, we first present a mechanism for filtering RTCP receiver reports sent from receivers to the whole session. The proposed filtering mechanism provides a classification of receivers according to a predefined similarity measure. An end-to-end source and FEC rate control based on this distributed feedback aggregation mechanism coupled with a video layered coding system is then described. The number of layers, their rate, and their levels of protection are adapted dynamically to aggregated feedbacks. The algorithms have been validated with the NS2 network simulator.