Simone Croci

Temporally coherent local tone mapping of HDR video

Recent subjective studies showed that current tone mapping operators either produce disturbing temporal artifacts, or are limited in their local contrast reproduction capability. We address both of these issues and present an HDR video tone mapping operator that can greatly reduce the input dynamic range, while at the same time preserving scene details without causing significant visual artifacts. To achieve this, we revisit the commonly used spatial base-detail layer decomposition and extend it to the temporal domain. We achieve high quality spatiotemporal edge-aware filtering efficiently by using a mathematically justified iterative approach that approximates a global solution. Comparison with the state-of-the-art, both qualitatively, and quantitatively through a controlled subjective experiment, clearly shows our methods advantages over previous work. We present local tone mapping results on challenging high resolution scenes with complex motion and varying illumination. We also demonstrate our methods capability of preserving scene details at user adjustable scales, and its advantages for low light video sequences with significant camera noise.

Lighting and Occlusion in a Wave‐Based Framework

We present novel methods to enhance Computer Generated Holography (CGH) by introducing a complex‐valued wave‐based occlusion handling method. This offers a very intuitive and efficient interface to introduce optical elements featuring physically‐based light interaction exhibiting depth‐of‐field, diffraction, and glare effects. Fur‐thermore, an efficient and flexible evaluation of lit objects on a full‐parallax hologram leads to more convincing images. Previous illumination methods for CGH are not able to change the illumination settings of rendered holo‐grams. In this paper we propose a novel method for real‐time lighting of rendered holograms in order to change the appearance of a previously captured holographic scene. These functionalities are features of a bigger wave‐based rendering framework which can be combined with 2D framebuffer graphics. We present an algorithm which uses graphics hardware to accelerate the rendering.

Saliency-Based Sharpness Mismatch Detection For Stereoscopic Omnidirectional Images

In this paper, we present a novel sharpness mismatch detection (SMD) approach for stereoscopic omnidirectional images (ODI) for quality control within the post-production workflow, which is the main contribution. In particular, we applied a state of the art SMD approach, which was originally developed for traditional HD images, and extended it to stereoscopic ODIs. A new efficient method for patch extraction from ODIs was developed based on the spherical Voronoi diagram of evenly distributed points on the sphere. The subdivision of the ODI into patches allows an accurate detection and localization of regions with sharpness mismatch. A second contribution of the paper is the integration of saliency into our SMD approach. In this context, we introduce a novel method for the estimation of saliency maps from viewport data of head-mounted displays (HMD). Finally, we demonstrate the performance of our SMD approach with data collected from a subjective test with 17 participants.

Real-time temporally coherent local HDR tone mapping

Subjective studies showed that most HDR video tone mapping operators either produce disturbing temporal artifacts, or are limited in their local contrast reproduction capability. Recently, both these issues have been addressed by a novel temporally coherent local HDR tone mapping method, which has been shown, both qualitatively and through a subjective study, to be advantageous compared to previous methods. However, this methods high-quality results came at the cost of a computationally expensive workflow that could only be executed offline. In this paper, we present a modified algorithm which builds upon the previous work by redesigning key components to achieve real-time performance. We accomplish this by replacing the optical flow based per-pixel temporal coherency with a tone-curve-space alternative. This way we eliminate the main computational burden of the original method with little sacrifice in visual quality.

Robust calibration of broadcast cameras based on ellipse and line contours

Professional TV studio footage often poses specific challenges to camera calibration due to lack of features and complex camera operation. As available algorithms often fail, we propose a novel approach based on robust tracking of ellipse and line features of a predefined logo. We further devise a predictive and iterative estimation algorithm, which incorporates confidence measures and filtering. Our results validate accuracy and reliability of our approach, demonstrated with challenging professional footage.

Scanners Test Report

For the digital restoration of a film the digitalization of it plays an important role. The color information present in the film and represented by the densities of the dyes must be transferred to the pixels of the scan preferably without loss. This report tries to understand how different scanners transfer this information for some film materials commonly used in the past.

Art-directable Continuous Dynamic Range video

We present a novel, end-to-end workflow for content creation and distribution to a multitude of displays that have different dynamic ranges. The emergence of new, consumer level HDR displays with various peak luminances expected in 2015 gives rise to two new research questions: (i) how can the raw source content be graded for a diverse set of displays both efficiently and without restricting artistic freedom, and (ii) how can an arbitrary number of graded video streams be represented and encoded in an efficient way. In this work we propose a new editing paradigm which we call dynamic range mapping to obtain a novel Continuous Dynamic Range (CDR) video representation, where the luminance of the video content, instead of being a scalar value, is defined as a continuous function of the display dynamic range. We present an interactive interface where CDR videos can be efficiently created while providing full artistic control. In addition, we discuss the efficient approximation of CDR video using a polynomial series approximation, and its encoding and distribution to an arbitrary set of target displays. We validate our workflow in a subjective study, which suggests that a visually lossless CDR video representation can be achieved with little bandwidth overhead. Our solution can be implemented easily in the current distribution infrastructure and consists of transmitting two gradings and an additional meta-data stream, which occupies less than 13% current standard video distribution bandwidth. Graphical abstractDisplay Omitted HighlightsA pipeline for creation and distribution of HDR content for a variety of displays.We allow the creation of Continuous Dynamic Range video with full artistic control.An efficient representation of CDR video using a series approximation.We present a demonstration of efficient encoding of Continuous Dynamic Range video.