By combining four different open standards belonging to the ISO/IEC JTC1/SC29 WG11 (a.k.a. MPEG) and W3C, this paper advances an architecture for mobile, medical oriented virtual collaborative environments. The various users are represented according to MPEG-UD (MPEG User Description) while the security issues are dealt with by deploying the WebID principles. On the server side, irrespective of their elementary types (text, image, video, 3D, …), the medical data are aggregated into hierarchical, interactive multimedia scenes which are alternatively represented into MPEG-4 BiFS or HTML5 standards. This way, each type of content can be optimally encoded according to its particular constraints (semantic, medical practice, network conditions, etc.). The mobile device should ensure only the displaying of the content (inside an MPEG player or an HTML5 browser) and the capturing of the user interaction. The overall architecture is implemented and tested under the framework of the MEDUSA European project, in partnership with medical institutions. The testbed considers a server emulated by a PC and heterogeneous user devices (tablets, smartphones, laptops) running under iOS, Android and Windows operating systems. The connection between the users and the server is alternatively ensured by WiFi and 3G/4G networks.
KEYWORDS: Video, Image quality, Molybdenum, Visualization, Digital watermarking, Statistical analysis, 3D displays, Principal component analysis, Color vision, 3D image reconstruction
This paper investigates three key issues related to full reference subjective quality evaluation tests for stereoscopic
video, namely, the number of quality levels on the grading scale, the number of observers in the evaluation panel,
and the inter-gender variability. It is theoretically demonstrated that the scores assigned by the observers on a
continuous grading scale can be a posteriori mapped to any discrete grading scale, with controlled statistical
accuracy. The experiments, performed in laboratory conditions, consider image quality, depth perception and visual
comfort. The original content (i.e. the full reference) is represented by the 3DLive corpus, composed of 2 hours 11
minutes of HD 3DTV content. The modified content (i.e. the content to be evaluated) is obtained by watermarking
this corpus with four methods. A panel of 60 observers (32 males and 28 females) was established from which
further randomly selected sub-panels of 30 and 15 observers were also subsequently extracted. In order to simulate a
continuous scale, the subjective evaluation was carried out on 100 quality levels, which are a posteriori mapped to
discrete scales of q quality levels, with q between 2 and 9. The statistical investigation focused on the Mean Opinion
Score and considered three types of statistical inferences: outliers detection, confidence limits, and paired t-tests.
KEYWORDS: Image quality, Video, Digital watermarking, Visualization, 3D displays, Televisions, 3D image processing, 3D image reconstruction, Reconstruction algorithms, Transparency
By reconsidering some two-dimensional video inherited approaches and by adapting them to the stereoscopic video content and to the human visual system peculiarities, a new disparity map is designed. First, the inner relation between the left and the right views is modeled by some weights discriminating between the horizontal and vertical disparities. Second, the block matching operation is achieved by considering a visual related measure (normalized cross correlation) instead of the traditional pixel differences (mean squared error or sum of absolute differences). The advanced three-dimensional (3-D) video-new three step search (3DV-NTSS) disparity map (3-D Video-New Three Step Search) is benchmarked against two state-of-the-art algorithms, namely NTSS and full-search MPEG (FS-MPEG), by successively considering two corpora. The first corpus was organized during the 3DLive French national project and regroups 20 min of stereoscopic video sequences. The second one, with similar size, is provided by the MPEG community. The experimental results demonstrate the effectiveness of 3DV-NTSS in both reconstructed image quality (average gains between 3% and 7% in both PSNR and structural similarity, with a singular exception) and computational cost (search operation number reduced by average factors between 1.3 and 13). The 3DV-NTSS was finally validated by designing a watermarking method for high definition 3-D TV content protection.
Watermarking already imposed itself as an effective and reliable solution for conventional multimedia content
protection (image/video/audio/3D). By persistently (robustly) and imperceptibly (transparently) inserting some extra
data into the original content, the illegitimate use of data can be detected without imposing any annoying constraint
to a legal user. The present paper deals with stereoscopic image protection by means of watermarking techniques.
That is, we first investigate the peculiarities of the visual stereoscopic content from the transparency and robustness
point of view. Then, we advance a new watermarking scheme designed so as to reach the trade-off between
transparency and robustness while ensuring a prescribed quantity of inserted information. Finally, this method is
evaluated on two stereoscopic image corpora (natural image and medical data).
The watermarking state of the art exhibits the hybrid methods combining spread spectrum and side information principles.
The present study is focussed on speeding up such an algorithm (jointly patented by SFR - Vodafone Group and Institut
Telecom). The dead lock on the reference method is first identified: the embedding module accounts for 90% of the whole
watermarking chain and that more than 99% of this time is spent on applying an attack procedure (required in order to grant
a good robustness to this method). The main issue of the present study is to deploy Monte Carlo generators accurately
representing the watermarking attacks. In this respect, two difficulties should be overcome. First, accurate statistical models
for the watermarking attacks should be obtained. Secondly, efficient Monte Carlo simulators should be deployed for these
models. The last part of the study was devoted to the experimental validations. The mark is inserted in the (9,7) DWT
representation of video sequence. Several types of attacks have been considered (linear and non-linear filters, geometrical
transformations, ...). The quantitative results proved that the data payload, transparency and robustness properties have
been inherited from the reference method. However, the watermarking speed was increased by a factor of 80.
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