François-Olivier Devaux

A Flexible Hardware JPEG 2000 Decoder for Digital Cinema

The image compression standard JPEG 2000 proposes a large set of features that is useful for todays multimedia applications. Unfortunately, it is much more complex than older standards. Real-time applications, such as digital cinema, require a specific, secure, and scalable hardware implementation. In this paper, a decoding scheme is proposed with two main characteristics. First, the complete scheme takes place in a field-programmable gate array without accessing any external memory, allowing integration in a secured system. Second, a customizable level of parallelization allows to satisfy a broad range of constraints, depending on the signal resolution. The resulting architecture is therefore ready to meet upcoming digital cinema specifications

Secure and Low Cost Selective Encryption for JPEG2000

Selective encryption is a new trend in content protection. It aims at reducing the amount of data to encrypt while achieving a sufficient and inexpensive security. This approach is particularly desirable in constrained communication (real time networking with delay constraints, mobile communication with limited computational power...). In this paper we introduce selective encryption from information theory point of view. We define a set of evaluation criteria for selective encryption algorithms and propose a novel selective encryption algorithm for JPEG2000 compressed images satisfying all these criteria. The main contribution of this proposal consists of reaching the minimum amount of data to encrypt regarding a given level of security and target application requirements. For this purpose, we exploit the R-D optimization performed by JPEG2000 EBCOT algorithm.

A Flexible Video Transmission System Based on JPEG 2000 Conditional Replenishment with Multiple References

The image compression standard JPEG 2000 offers a high compression efficiency as well as a great flexibility in the way it accesses the content in terms of spatial location, quality level, and resolution. This paper explores how transmission systems conveying video surveillance sequences can benefit from this flexibility. Rather than transmitting each frame independently as it is generally done in the literature for JPEG 2000 based systems, we adopt a conditional replenishment scheme to exploit the temporal correlation of the video sequence. As a first contribution, we propose a rate-distortion optimal strategy to select the most profitable packets to transmit. As a second contribution, we provide the client with two references, the previous reconstructed frame and an estimation of the current scene background, which improves the transmission system performances.

Remote Interactive Browsing of Video Surveillance Content Based on JPEG 2000

In video surveillance applications, pre-stored images are likely to be accessed remotely and interactively upon user request. In such a context, the JPEG 2000 still image compression format is attractive because it supports flexible and progressive access to each individual image of the pre-stored content, in terms of spatial location, quality level, as well as resolution. However, when the client wants to play consecutive frames of the video sequence, the purely INTRA nature of JPEG 2000 dramatically penalizes the transmission efficiency. To mitigate this drawback, conditional replenishment mechanisms are envisioned. They convey arbitrary spatio-temporal segments of the initial video sequence directly through sporadic and rate-distortion (RD) optimized refresh of JPEG 2000 packets. Hence, they preserve JPEG 2000 compliance, while saving transmission resources. The replenishment algorithms proposed in this paper are original in two main aspects. First, they exploit the specificities of the JPEG 2000 codestream structure to balance the accuracy (in terms of bit-planes) of the replenishment across image subbands in a (RD)-optimal way. Second, they take into account the still background nature of video surveillance content by maintaining two reference images at the receiver. One reference is the last reconstructed frame, as proposed in the original replenishment framework. The other is a dynamically computed estimate of the scene background, which helps to recover the background after a moving object has left the scene. As an additional contribution, we demonstrate that the embedded nature of the JPEG 2000 codestream easily supports prioritization of semantically relevant regions of interest while browsing video content. An interesting aspect of this JPEG 2000-based prioritization is that it can be regulated a posteriori, after the codestream generation, based on the interest expressed by the user at browsing time. Simulation results demonstrate the efficiency and flexibility of the approach compared to INTER-based solutions.

Optimal JPWL forward error correction rate allocation for robust JPEG 2000 images and video streaming over mobile ad hoc networks

Based on the analysis of real mobile ad hoc network (MANET) traces, we derive in this paper an optimal wireless JPEG 2000 compliant forward error correction (FEC) rate allocation scheme for a robust streaming of images and videos over MANET. The packet-based proposed scheme has a low complexity and is compliant to JPWL, the 11th part of the JPEG 2000 standard. The effectiveness of the proposed method is evaluated using a wireless Motion JPEG 2000 client/server application; and the ability of the optimal scheme to guarantee quality of service (QoS) to wireless clients is demonstrated.

Dynamic channel coding for efficient motion JPEG2000 video streaming over mobile ad-hoc networks

In this work, we present a dynamic channel coding scheme for robust transmission of JPEG2000 codestreams over Mobile Ad-hoc Networks (MANET). The proposed system, based on dynamic Forward Error Correction (FEC) rate allocation allied to layered Unequal Error Protection (UEP), is implemented according to the main recommendations of Wireless JPEG2000 standard final draft. We demonstrate that dynamic FEC rate allocation outperforms a priori FEC rate allocation. Going straightforward we validate the proposed scheme by deriving interesting results from Motion JPEG2000 video streaming over real MANET data traces. This application, developed within the European IST WCAM project, validates wireless JPEG2000 standards recommendations and is a step toward guaranteeing Quality of Service (QoS) in wireless JPEG2000 based data streaming systems.

Parity bit replenishment for JPEG 2000-based video streaming

This paper envisions coding with side information to design a highly scalable video codec. To achieve fine-grained scalability in terms of resolution, quality, and spatial access as well as temporal access to individual frames, the JPEG 2000 coding algorithm has been considered as the reference algorithm to encode INTRA information, and coding with side information has been envisioned to refresh the blocks that change between two consecutive images of a video sequence. One advantage of coding with side information compared to conventional closed-loop hybrid video coding schemes lies in the fact that parity bits are designed to correct stochastic errors and not to encode deterministic prediction errors. This enables the codec to support some desynchronization between the encoder and the decoder, which is particularly helpful to adapt on the fly pre-encoded content to fluctuating network resources and/or user preferences in terms of regions of interest. Regarding the coding scheme itself, to preserve both quality scalability and compliance to the JPEG 2000 wavelet representation, a particular attention has been devoted to the definition of a practical coding framework able to exploit not only the temporal but also spatial correlation among wavelet subbands coefficients, while computing the parity bits on subsets of wavelet bit-planes. Simulations have shown that compared to pure INTRA-based conditional replenishment solutions, the addition of the parity bits option decreases the transmission cost in terms of bandwidth, while preserving access flexibility.

HVS-based quantization steps for validation of digital cinema extended bitrates

In Digital Cinema, the video compression must be as transparent as possible to provide the best image quality to the audience. The goal of compression is to simplify transport, storing, distribution and projection of films. For all those tasks, equipments need to be developed. It is thus mandatory to reduce the complexity of the equipments by imposing limitations in the specifications. In this sense, the DCI has fixed the maximum bitrate for a compressed stream to 250 Mbps independently from the input format (4K/24fps, 2K/48fps or 2K/24fps). The work described in this paper This parameter is discussed in this paper because it is not consistent to double/quadruple the input rate without increasing the output rate. The work presented in this paper is intended to define quantization steps ensuring the visually lossless compression. Two steps are followed first to evaluate the effect of each subband separately and then to fin the scaling ratio. The obtained results show that it is necessary to increase the bitrate limit for cinema material in order to achieve the visually lossless.

A flexible video server based on a low complex post-compression rate allocation

This paper proposes a highly flexible streaming video server that is particularly well suited for video-surveillance content. To achieve the required flexibility, the sequences are encoded with the JPEG 2000 coding scheme. To preserve compression efficiency, the temporal redundancy is exploited by a conditional replenishment technique. The main novelty of this paper consists in a post-compression rate allocation, which enables the server to adapt in real-time the content forwarded to heterogeneous clients using a single pre-compressed version of the sequence. An index is pre-calculated offline to reduce the computational load at the server while scheduling the packets in real-time, according to the needs and resources of the clients.