New Light Field Image Dataset

Recently, an emerging light field imaging technology, which enables capturing full light information in a scene, has gained a lot of interest. To design, develop, implement, and test novel algorithms in light field image processing and compression, the availability of suitable light field image datasets is essential. In this paper, a publicly available light field image dataset is introduced and described in details. The proposed dataset contains 118 light field images captured by using a Lytro Illum light field camera. Based on their content, acquired light field images were classified into ten different categories with various features covering wide range of potential usage, such as image compression and quality evaluation

COMPARISON OF 3D PORTABLE DISPLAY RESTITUTION TECHNIQUES BASED ON STEREO AND MOTION PARALLAX

Currently, the large majority of 3D display solutions rely on binocular perception phenomena. Furthermore, while 3D display technologies are already widely available for cinema and home or corporate use, only a few portable devices currently feature 3D display capabilities. In this paper, we study the alternative methods for restitution of 3D images on displays of commercially available portable devices and analyse their respective performance. This particularly includes the restitution method which uses multiscopic image data-set and which relies on motion parallax as an additional depth cue. The goal of this paper is to compare three different commercially available 3D display techniques, the auto-stereoscopic and anaglyph method which provide binocular depth cues and a method based on motion parallax. The subsequently conducted subjective quality tests show that the motion parallax based approach to present 3D images on consumer portable screen is an equivalent and quite competitive way in comparison to the above mentioned stereopsis based methods

Comparison of compression efficiency between HEVC/H.265 and VP9 based on subjective assessments

Current increasing effort of broadcast providers to transmit UHD (Ultra High Definition) content is likely to increase demand for ultra high definition televisions (UHDTVs). To compress UHDTV content, several alter- native encoding mechanisms exist. In addition to internationally recognized standards, open access proprietary options, such as VP9 video encoding scheme, have recently appeared and are gaining popularity. One of the main goals of these encoders is to efficiently compress video sequences beyond HDTV resolution for various scenarios, such as broadcasting or internet streaming. In this paper, a broadcast scenario rate-distortion performance analysis and mutual comparison of one of the latest video coding standards H.265/HEVC with recently released proprietary video coding scheme VP9 is presented. Also, currently one of the most popular and widely spread encoder H.264/AVC has been included into the evaluation to serve as a comparison baseline. The comparison is performed by means of subjective evaluations showing actual differences between encoding algorithms in terms of perceived quality. The results indicate a dominance of HEVC based encoding algorithm in comparison to other alternatives if a wide range of bit-rates from very low to high bit-rates corresponding to low quality up to transparent quality when compared to original and uncompressed video is considered. In addition, VP9 shows competitive results for synthetic content and bit-rates that correspond to operating points for transparent or close to transparent quality video

On the performance of objective metrics for omnidirectional visual content

Omnidirectional image and video have gained popularity thanks to availability of capture and display devices for this type of content. Recent studies have assessed performance of objective metrics in predicting visual quality of omnidirectional content. These metrics, however, have not been rigorously validated by comparing their prediction results with ground-truth subjective scores. In this paper, we present a set of 360-degree images along with their subjective quality ratings. The set is composed of four contents represented in two geometric projections and compressed with three different codecs at four different bitrates. A range of objective quality metrics for each stimulus is then computed and compared to subjective scores. Statistical analysis is performed in order to assess performance of each objective quality metric in predicting subjective visual quality as perceived by human observers. Results show the estimated performance of the state-of-the-art objective metrics for omnidirectional visual content. Objective metrics specifically designed for 360-degree content do not outperform conventional methods designed for 2D images

JPEG backward compatible coding of omnidirectional images

Omnidirectional image and video, also known as 360 image and 360 video, are gaining in popularity with the recent growth in availability of cameras and displays that can cope with such type of content. As omnidirectional visual content represents a larger set of information about the scene, it typically requires a much larger volume of information. Efficient compression of such content is therefore important. In this paper, we review the state of the art in compression of omnidirectional visual content, and propose a novel approach to encode omnidirectional images in such a way that they are still viewable on legacy JPEG decoders

Impact of interactivity on the assessment of quality of experience for light field content

The recent advances in light field imaging are changing the way in which visual content is captured, processed and consumed. Storage and delivery systems for light field images rely on efficient compression algorithms. Such algorithms must additionally take into account the feature-rich rendering for light field content. Therefore, a proper evaluation of visual quality is essential to design and improve coding solutions for light field content. Consequently, the design of subjective tests should also reflect the light field rendering process. This paper aims at presenting and comparing two methodologies to assess the quality of experience in light field imaging. The first methodology uses an interactive approach, allowing subjects to engage with the light field content when assessing it. The second, on the other hand, is completely passive to ensure all the subjects will have the same experience. Advantages and drawbacks of each approach are compared by relying on statistical analysis of results and conclusions are drawn. The obtained results provide useful insights for future design of evaluation techniques for light field content

A new approach to subjectively assess quality of plenoptic content

Plenoptic content is becoming increasingly popular thanks to the availability of acquisition and display devices. Thanks to image-based rendering techniques, a plenoptic content can be rendered in real time in an interactive manner allowing virtual navigation through the captured scenes. This way of content consumption enables new experiences, and therefore introduces several challenges in terms of plenoptic data processing, transmission and consequently visual quality evaluation. In this paper, we propose a new methodology to subjectively assess the visual quality of plenoptic content. We also introduce a prototype software to perform subjective quality assessment according to the proposed methodology. The proposed methodology is further applied to assess the visual quality of a light field compression algorithm. Results show that this methodology can be successfully used to assess the visual quality of plenoptic content

Subjective and objective evaluation of HDR video compression

Recent efforts by MPEG and research community to standardize high dynamic range (HDR) video compression require efficient objective metrics. This paper investigates how well the currently available metrics measure perceptual quality of HDR video. For this purpose, subjective tests were conducted using SIM2 HDR monitor and several video sequences provided by MPEG. The sequences were compressed with HEVC encoder in YCbCr420 10bit and YCbCr444 12bit formats. The results of subjective tests were correlated with objective metrics to identify suitable metrics to use for the objective evaluations of different HDR video coding solutions. A few variants of PSNR, as well as SSIM, MSE, VIFP, and especially HDR-VDP-2 metric, have high correlation with the subjective scores

JPEG backward compatible format for 3D content representation

Different formats and compression algorithms have been proposed for 3D video content, but 3D images are still mostly represented as a stereo pair only. However, for enhanced 3D rendering capabilities, such as depth perception adjustment or display size adaptation, additional depth data is necessary. To facilitate the standardization process of a common 3D format, backward compatibility with legacy technologies is necessary. In this paper, we propose to extend the JPEG file format, as the most popular image format, in a backward compatible manner to represent a stereo pair and additional depth data. We propose an architecture to achieve such backward compatibility with JPEG. The coding efficiency of a simple implementation of the proposed architecture is compared to the state of the art stereoscopic 3D image compression and storage formats

Quality Evaluation of HEVC and VP9 Video Compression in Real-Time Applications

Video consumption over Internet has increased significantly over the recent years and occupies the majority of the overall data traffic. To decrease the load on the Internet infrastructure and reduce bandwidth taken by video, higher efficiency video codecs, such as H.265/HEVC and VP9, have been developed. The availability of these two new competing video coding formats raises the question of which is more efficient in terms of rate-distortion and by how much they outperform the current state-of-the-art coding standard, H.264/AVC. This paper provides an answer to this difficult question for low-delay video applications, e.g., real-time video streaming/conferencing or video surveillance. The benchmarking of HEVC and VP9 video compression was conducted by means of subjective evaluations, assuming web browser playback, an uncontrolled environment, and HD video content. Considering a wide range of bit rates from very low to high bit rates, corresponding to low quality up to transparent quality (when compared to the original video), results show a clear advantage of HEVC with average bit rate savings of 59.5% when compared to AVC and 42.4% when compared to VP9