Objectification of perceptual image quality for mobile video

최근 국내 지상파 다채널 방송의 도입이 재 논의되고 있다. 본 연구에서는 지상파 다채널방송 도입으로 기존 방송 채널의 화질 열화에 대해 객관적 화질평가와 주관적 화질 평가를 통해 검증하였다. 객관적 화질 평가에서는 다채널 방송용 시스템이 기존 방송보다 높은 PSNR을 보였다. 주관적 화질평가 결과도 MMS 시스템의 화질 열화를 인지하기 어려운 것으로 나타났다. 특히 시사 다큐멘터리와 연예 오락 분야에서는 다채널 방송에서 화질이 더 개선될 것으로 나타나고 있다. 따라서 2006년과 2008년 연구 결과와 비교할 때, 방송 기술의 발전으로 다채널 방송 도입에 따른 화질열화 우려가 해소됨에 따라 다채널 서비스 도입에 필요한 정책마련이 시급히 요구된다. Currently, The terrestrial MMS(Multi Mode Service) is considering to be adapted in the Korea. The objective and subjective video quality test was carried out to verify the current TV channel's video quality degradation by the MMS. In the objective assessment, MMS system showed better PSNR than current system. In the subjective assesment result, It's hard to find the perceive video quality degradation at overall assesment. Even though, The MMS's video quality will be improved at the documentary and entertainment genre. Comparing with the previous research at 2006 and 2008, It's the time to give the benefit of broadcasting technology to the people.

The Video Quality Experts Group (VQEG) is preparing a programme of subjective multimedia quality tests. The results from these tests will be used to evaluate the performance of competing objective multimedia quality metrics. The reliability of the subjective test data is of great importance for VQEG's task. This paper provides an overview of VQEG's multimedia ad-hoc group. The work of this group will require subjective tests to be performed by laboratories located in Europe, Asia and North America. For VQEG's multimedia work to be successful, the subjective assessment methodology must be precisely defined and produce reliable and repeatable subjective quality data. Although international standards covering multimedia quality assessment methods are in force, there remains some uncertainty regarding the most effective approach to assessing the subjective quality of multimedia. A review of existing methods is provided. Two experiments are presented investigating the suitability of alternative subjective assessment methods (single-stimulus ACR and SAMVIQ). The results of these experiments are discussed within the context of the VQEG multimedia testing programme.

In this paper some possibilities of using the GPGPU programming techniques for a fast estimation of the recently proposed combined video quality metric are discussed. Such metric consists of three state-of-the-art image quality assessment metrics applied using frame-by-frame analysis with appropriate weighting coefficients. Since this combined metric is better correlated with subjective quality scores than each of its components, especially for the contaminations typical for the wireless transmission of compressed video data, the next step is related to its efficient implementation useful for real-time applications. In the paper an efficient implementation of the estimated combined metric is presented together with the verification of its linear correlation with subjective video quality evaluations performed using the LIVE Wireless Video Quality Assessment Database containing 160 video files with four types of distortions and their Differential Mean Opinion Score (DMOS) values.

The purpose of this study was to examine the impact of the desirability of content on viewers' ratings of subjective video quality. Most subjective video quality studies use short-duration clips that are specially designed to exercise the encoding algorithms and do not consider the desirability of the content as a variable. In four studies, we employed a total of 100 participants and 180 movie clips encoded at nine levels from 550 kbps up to DVD quality. Participants viewed clips that were 2 min in length and then were asked about video quality of the clips and desirability of the movie content. The results of these studies show that there is a strong correlation between the desirability of movie content and subjective ratings of video quality. This strong relationship holds across a wide range of encoding levels and movie content when that content is viewed under longer, more naturalistic viewing conditions. The effects of content should be considered when evaluating the subjective quality of encoded video content, as these effects can be as large as those seen between low- and high-quality encodings. Researchers and practitioners trying to determine acceptable levels of video quality for actual consumption by consumers may find that the results and methods described here allow for a more accurate assessment of levels of video quality that are acceptable in a fielded service.

We introduce a new video quality database that models video distortions in heavily-trafficked wireless networks and that contains measurements of human subjective impressions of the quality of videos. The new LIVE Mobile Video Quality Assessment (VQA) database consists of 200 distorted videos created from 10 RAW HD reference videos, obtained using a RED ONE digital cinematographic camera. While the LIVE Mobile VQA database includes distortions that have been previously studied such as compression and wireless packet-loss, it also incorporates dynamically varying distortions that change as a function of time, such as frame-freezes and temporally varying compression rates. In this article, we describe the construction of the database and detail the human study that was performed on mobile phones and tablets in order to gauge the human perception of quality on mobile devices. The subjective study portion of the database includes both the differential mean opinion scores (DMOS) computed from the ratings that the subjects provided at the end of each video clip, as well as the continuous temporal scores that the subjects recorded as they viewed the video. The study involved over 50 subjects and resulted in 5,300 summary subjective scores and time-sampled subjective traces of quality. In the behavioral portion of the article we analyze human opinion using statistical techniques, and also study a variety of models of temporal pooling that may reflect strategies that the subjects used to make the final decision on video quality. Further, we compare the quality ratings obtained from the tablet and the mobile phone studies in order to study the impact of these different display modes on quality. We also evaluate several objective image and video quality assessment (IQA/VQA) algorithms with regards to their efficacy in predicting visual quality. A detailed correlation analysis and statistical hypothesis testing is carried out. Our general conclusion is that existing VQA algorithms are not well-equipped to handle distortions that vary over time. The LIVE Mobile VQA database, along with the subject DMOS and the continuous temporal scores is being made available to researchers in the field of VQA at no cost in order to further research in the area of video quality assessment.

Today in many homes big TV screens and hifi systems are common. But is the perception of subjective video quality under professional test conditions the same as at home? Therefore we examined two things: How large is the influence of the presentation device but also the influence of the soundtrack, both in HDTV (1080p50). Previous work has shown that a difference is noticeable, but there have not been studies with consumer devices, yet. It was also shown that there is an influence of the soundtrack, but only in SDTV or lower resolutions. Therefore we conducted subjective video tests: One test with different devices, a 23-inch-reference monitor, a high quality 56-inch-LCD-TV and an HD-projector, and one test in which we presented a soundtrack on a 7.1-channel hifi system in addition to the HD-projector. The results show two things: First the test subjects had a higher quality of experience with the consumer devices than with the reference monitor, although the video quality of the reference monitor itself was rated better in an additional questionnaire and the mean opinion score (MOS). The second result is that there is no significant difference in the MOS between showing the videos on the projector with or without sound.

Subjective quality feedback by actual human viewers is crucial for reliable evaluation of various solutions and configurations for video processing or encoding. However, it is generally a time consuming and expensive process. Therefore, in many cases evaluation of video quality is done using objective measures, which may be poorly correlated with actual subjective results. In order to address this issue, we have developed VISTA (VIsual Subjective Testing Application), an easy to use application for visually comparing pairs of video sequences played synchronously side by side, and a user interface for indicating the relative subjective quality of the two video sequences. In addition, we developed a system for automating the evaluation process called Auto-VISTA. The system receives as input guidelines for the required testing session, prepares the content to be compared, launches the app in a crowdsourcing Internet marketplace (such as Amazon Mechanical Turk), and performs collection and analysis of the results. Thus, obtaining large scale subjective feedback becomes cheap and accessible, which in turn allows for fast and reliable evaluation cycles of different video encoding and processing solutions, or tuning various configurations and settings for a given solution.

To perform Quality of Service (QoS) control of video communication more efficiently, it is necessary to develop an objective quality evaluation method for coded video. Many proposed conventional methods to obtain video quality require the availability of both reference and processed video sequence. However, in case of re-encoding the coded video stream at the receiver side where reference video sequence is not present, it is impossible to do such a full-reference evaluation. Therefore, we have developed a video quality evaluation model by using reduced reference for evaluated value obtained by SSCQE method. In this approach, we use some features extracted from reference video. It is called reduced-reference method by VQEG. Transmitting these features with coded video, the proposed model can estimate the video quality, even in the absent of the full original video in the decoder side. The video quality rating obtained from the proposed model shows good agreement with subjective quality.

Most of candidate methods for compression of mobile stereo video apply block-transform based compression based on the H-264 standard with quantization of transform coefficients driven by quantization parameter (QP). The compression ratio and the resulting bit rate are directly determined by the QP level and high compression is achieved for the price of visually noticeable blocking artifacts. Previous studies on perceived quality of mobile stereo video have revealed that blocking artifacts are the most annoying and most influential in the acceptance/rejection of mobile stereo video and can even completely cancel the 3D effect and the corresponding quality added value. In this work, we address the problem of deblocking of mobile stereo video. We modify a powerful non-local transform-domain collaborative filtering method originally developed for denoising of images and video. The method employs grouping of similar block patches residing in spatial and temporal vicinity of a reference block in filtering them collaboratively in a suitable transform domain. We study the most suitable way of finding similar patches in both channels of stereo video and suggest a hybrid four-dimensional transform to process the collected synchronized (stereo) volumes of grouped blocks. The results benefit from the additional correlation available between the left and right channel of the stereo video. Furthermore, addition sharpening is applied through an embedded alpha-rooting in transform domain, which improve the visual appearance of the deblocked frames.

With the development of image compress technology, video is used more and more often. For the complexity of the subjective video quality estimation, many researchers are pay attention to the objective video quality assessment. In this paper, we proposed a color video quality assessment based on edge-color distortion. First, the edge and the color distortion models are introduced. Then, the response functions of HVS to the two models are given by analyzing relation between predicted value of the two models and the subjective quality estimation. Finally, the functions are integrated into an equation which is used to measure the color video quality by using multiple linear regression analysis. The proposed method is tested on the video quality experts group (VQEG) Phase I FR-TV test data set. Experiments show that it has good correlation with perceived video quality.

Arrow’s Impossibility Theorem inspired subjective image quality assessment approach

Well-performed Video quality assessment (VQA) method should be consistent with human visual systems for better prediction accuracy. In this paper, we propose a VQA method using motion-compensated temporal filtering (MCTF) and manifold feature similarity. To be more specific, a group of frames (GoF) is first decomposed into a temporal high-pass component (HPC) and a temporal low-pass component (LPC) by MCTF. Following this, manifold feature learning (MFL) and phase congruency (PC) are used to predict the quality of temporal LPC and temporal HPC respectively. The quality measures of the LPC and the HPC are then combined as GoF quality. A temporal pooling strategy is subsequently used to integrate GoF qualities into an overall video quality. The proposed VQA method appropriately processes temporal information in video by MCTF and temporal pooling strategy, and simulate human visual perception by MFL. Experiments on publicly available video quality database showed that in comparison with several state-of-the-art VQA methods, the proposed VQA method achieves better consistency with subjective video quality and can predict video quality more accurately.

Block effect is one of the most annoying artifacts in digital video processing and is especially visible in low-bitrate applications, such as mobile video. To alleviate this problem, we propose an adaptive quantization method for inter frames that can reduce visible block effect in DCT-based video coding. In the proposed method, a set of quantization matrices are constructed before processing the video data. Matrices are constructed by exploiting the temporal frequency limitations of human visual system. The method is adaptive to motion information and is able to select an appropriate quantization matrix for each inter-coded block. Based on the experimental results, the proposed scheme can achieve better subjective video quality compared to conventional flat quantization especially at low-bitrate application. Moreover, it does not introduce extra computational cost in software implementation. This method does not change standard bitstream syntax, so it can be directly applied to many DCT-based video codecs. A potential application could be for mobile phone and other digital devices with low-bitrate requirement.

There is a significant increase in mobile internet usage resulting in demand for traffic volume, frequency efficiency and energy and cost reduction, for which small cell networks are expected to play a key role. Due to high bandwidth requirement, mobile health applications (m-health) and medical video streaming in particular will benefit from small cell networks in terms of Quality of Service (QoS) and Quality of Experience (QoE) enhancements. This paper presents content-aware and device-aware medical Quality of Experience evaluations in terms of subjective (e.g. MOS) and objective (e.g. PSNR and SSIM) quality metrics obtained over small cell networks. Furthermore, we address the following two main research questions: (1) How significant is ultrasound video content type in determining medical QoE? (2) How much of a role does the display device play in medical experts’ diagnostic experience? The former is answered through the content classification of ultrasound video sequences based on their spatio-temporal features and validating their significance through medical experts’ subjective ratings. The latter is answered by conducting a subjective experiment of the ultrasound video sequences across multiple devices, ranging in screen size and resolution.

Video quality can be measured using both subjective and objective assessment methods. Subjective experiments are crucially important as they constitute a benchmark for evaluating the performance of objective quality metrics. Subjective quality assessment of television pictures has received extensive attention from experts over the past decades. On the other hand, emerging applications such as PC-based video streaming and mobile video streaming require new subjective test methodologies. Although some recent studies have compared different test methodologies and procedures, most concerned television pictures. No studies for multimedia-type video really validated the repeatability and reliability of the assessment method and the experimental procedure. This paper outlines a methodology for conducting subjective evaluation of video quality for multimedia applications in a repeatable and reliable manner across different laboratories. Using video material at low-resolution, low-bit rate and low-frame rate, the same experiment was conducted by two different laboratories, i.e. test material was identical in both experiments. Laboratory set-up was different, i.e. different computers and display panels were used, and viewing distance was not fixed. Results show that quality ratings obtained in both experiments are statistically identical. This is an important validation step for the Video Quality Experts Group, which will conduct an ambitious campaign of subjective experiments using many different test laboratories.