Benjamin Gadat

A simple Multiple Description Coding scheme for improved peer-to-peer video distribution over mobile links

This paper presents an adaptation of peer-to-peer diffusion strategies of video over mobile links based on the use of multiple description coding. The system architecture, including the used overlay algorithm (the unstructured GIA algorithm) and video coding with multiple description coding (MDC), are presented as well as their interest in this context. Simulation results illustrate the approach, showing the interest of using MDC vs. a single description coding solution. The proposed simulation framework involves an H.264/AVC video codec with two descriptions and a simple adaptation of the overlay algorithm.

Data supervision for adaptively transcoded video surveillance over wireless links

This paper describes a solution for on-the-fly adapting the parameters of a video surveillance streams to system varying conditions, both in terms of data to be transmitted (number of streams to be sent) and of transmission conditions (quality of the available wireless link). This solution has been inserted in the system architecture of the EUREKA CELTIC BOSS project for enhancing the security of passengers inside commuter trains. The dynamic adaptation solution proposed allows to offer better Quality of Service (QoS) for critical streams, as well as enhanced robustness to channel conditions variations. Simulation results as well as integration of this feature in the BOSS project demonstrator are presented to illustrate the gains this approach can offer.

Blind frame synchronization of reed-solomon codes: Non-binary VS. binary approach

We consider in this paper the problem of blind frame synchronization of systems using Reed-Solomon (RS) codes and other related families. We present first of all three techniques of blind frame synchronization based on the non-binary parity check matrix of RS codes. While the first two techniques involve the calculation of hard and soft values of the syndrome elements respectively, the third one perform an adaptation step of the parity check matrix before applying the soft criterion. Although RS codes are constructed from non-binary symbols, we show in this paper that it is also possible to synchronize them using the binary image expansion of their parity check matrix. Simulation results show that the synchronization algorithm based on the adaptation of the binary parity check matrix of RS codes has the best synchronization performance among all other techniques. Furthermore, the Frame Error Rate (FER) curves obtained after synchronization and decoding are very close to the perfect synchronization curves.

Application control for fast adaptive error resilient H.264/AVC streaming over IP wireless networks

Following the joint source and channel coding paradigm, we propose in this article an application controlling strategy to allow fast adaptation of multimedia transmission to the impairments of an IP wireless network. To this purpose, a semi-analytical prediction algorithm of the video stream perceived quality of service (PQoS) expressed as the end-to-end distortion (EED) is introduced, that takes into account the distortions due to the diverse treatments of compression, transmission and decoding for a group of pictures (GOP) subject to an imperfect communication channel. This algorithm allows to define the parameters providing the best perceived quality at the receiver side in terms both of compression and optionally of error correcting redundancy insertion to minimise the error impact with a GOP adaptation rate, as demonstrated by the results presented for H.264/AVC streams transmitted in various channel configurations.

Embedding Protection Inside H.264/AVC and SVC Streams

A backward compatible error-protection mechanism embedded into the H.264 (AVC or SVC) syntax is described. It consists of the addition into the H.264 bitstream of supplementary network abstraction layer (NAL) units that contain forward error-correction (FEC) data generated by a block error-correction code. The proposed mechanism allows to leave the original information bits and NAL units intact and does not rely on any side information or extra signalling coming from lower layers, ensuring backward compatibility with the standard syntax. Simulation results obtained with Reed-Solomon and Low-density parity check error-correcting codes show significant improvements for both erroneous and lossy transmission channel configurations.

End-to-End Application Control of Video Streaming: Implementation and Performance Evaluation

This paper presents a solution for multimedia streaming adaptation to the conditions of the network. Since video content contains intrinsically redundant information, different degrees of compression can be applied. At the same time, if several errors and losses affect the communication, the transmission can be protected by correcting codes. The FP7 ICT OPTIMIX project aims at optimising the transmission of a video stream to a single user or to a group of clients, connected to the internet with a portable wireless device. In this context, a controlling process, coupling video compression to Forward Error Correction and exploiting feedback information coming from the clients, has been proposed in [1]. This paper presents the system architecture proposed for the use of this controller and evaluates the performance of the proposed scheme for both point to point and point to multi-point transmissions.