deletions | additions       diff --git a/section_Objective_measures_of_quality__.tex b/section_Objective_measures_of_quality__.tex  index 218d95c..645a66d 100644  --- a/section_Objective_measures_of_quality__.tex  +++ b/section_Objective_measures_of_quality__.tex 
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Currently there is an increasing need for objective measures of the quality of navigation but not so many solutions have been devised so far. Preliminary studies have analyzed the behavior of state-of-the-art 2D full reference metrics (e.g. PSNR, SSIM) applied to FVV content. As expected, these metrics are not able to predict the MOS basically due to the presence of artifacts that are typical of this kind of content as previously explained.  A detailed study of this issue is presented by the authors in [1]. In this paper the correlation between the DMOS collected by subjective experiments and the one predicted by 2D image quality metrics is analyzed. The performed analysis has highlighted that none of the considered 2D image quality metrics is able to reliably predict the MOS and that this correlation slightly increases if content characteristics are taken into account.   A similar conclusion is reached in the studies carried out in [4]. In this case, the impact of the synthesis process is evaluated in stereoscopic conditions…. conditions and the comparison with the monoscopic case is also addressed.  The work presented by the authors in [3] includes some guidelines to be used for defining new quality metrics for 3D synthesized view assessment. In particular, an analysis of the performances of twelve 2D image quality metrics is performed on a database created by three multiview sequences processed with seven DIBR algorithms to create new viewpoints. Subjective experiments have been carried out on 43 observers in order to efficiently evaluate the ability of these metrics to predict the MOS. Also in this case the correlation is poor and the results are dependent on the sequence content. Based on the achieved results, the authors propose some improvements that could be taken into account for the design of new quality metrics. In particular the attention is focused on the location of the artifacts that are created by the synthesis process. In fact, the humans are more sensible to disocclusions especially because they appear along contours. A first attempt to apply these findings to SSIM reveals an increased correlation with the MOS.   For this reason the research community started moving towards the definition of quality metrics able to take into account the characteristics of the FVV content.  In [1] an image quality metric, 3DswIM, is presented for 3D synthesized views. This is a full-reference metric that takes into account DIBR-specific distortions. It is based on the analysis of statistical features extracted from the wavelet decomposition of the synthesized and original images. The performed experiments show improved performances with respect to 2D image quality metrics.