Single Stimulus Continuous Quality Evaluation Research Articles

Quality perception of specific chromatic impairments

This work was motivated by previous studies on the perceptual influence of chromatic impairments, where was observed that specific chromatic impairments might have a different influence, related to the represented content. Hence, in this study, chromatic impairments were applied to specific color clusters and the resulting perceptual influence was analyzed. The applied chromatic impairments influence on the images naturalness was assessed using a Single Stimulus Continuous Quality Evaluation (SSCQE) and the Mean Opinion Score (MOS) was calculated. Furthermore, during the image assessment, the eye movements were registered using an eye tracking device and the Relative Fixation Time (RFT) was computed. It was concluded that the induced chromatic impairments, lead to lower MOS values than the original images, revealing a perception of quality loss. Furthermore, when nature colors are changed, subjects revealed a larger perception of the impairment, resulting in smaller MOS and producing evident changes in the RFT’s. The comparative analysis between the MOS and the RFT’s reveals high Pearson Correlation Coefficient (PCC) results (p = 0.79 ± 0.14).

Implementation of Multimodal Interactive Continuous Scoring for 3D Quality of Experience

When watching videos in 3D space, viewers perceive dynamic levels of quality of experience accompanied by visual immersion. To measure these dynamics, a reliable methodology is needed to gauge subjective viewer experience. This paper proposes a new methodology called multimodal interactive continuous scoring of quality (MICSQ). MICSQ is comprised of device interaction processes between the 3D display and tablet assessment tool and human interaction processes between the subject and tablet. When MICSQ device interaction takes place over wireless network protocols, such as TCP/IP or Bluetooth, it efficiently handles the diverse viewing environment. Therefore, there is a high degree of freedom to perform subjective assessment in certain viewing environments in terms of multimodal cues (aural and tactile senses), diverse illumination conditions including darkness, handheld portability over wireless networks, and real-time recording. Moreover, it is also possible for multiple subjects to simultaneously perform assessments in a large space, such as a movie theater. For the simulations, the server application in the 3D display was developed in Java, and the tablet device client application was developed with a mobile software development kit and functions optimally in commercial tablets. The experimental results demonstrate that MICSQ shows a higher reliability than the conventional single stimulus continuous quality evaluation method through the proposed implementation on a commercial tablet PC.

Multimodal Interactive Continuous Scoring of Subjective 3D Video Quality of Experience

People experience a variety of 3D visual programs, such as 3D cinema, 3D TV and 3D games, making it necessary to deploy reliable methodologies for predicting each viewer's subjective experience. We propose a new methodology that we call multimodal interactive continuous scoring of quality (MICSQ). MICSQ is composed of a device interaction process between the 3D display and a separate device (PC, tablet, etc.) used as an assessment tool, and a human interaction process between the subject(s) and the separate device. The scoring process is multimodal, using aural and tactile cues to help engage and focus the subject(s) on their tasks by enhancing neuroplasticity. Recorded human responses to 3D visualizations obtained via MICSQ correlate highly with measurements of spatial and temporal activity in the 3D video content. We have also found that 3D quality of experience (QoE) assessment results obtained using MICSQ are more reliable over a wide dynamic range of content than obtained by the conventional single stimulus continuous quality evaluation (SSCQE) protocol. Moreover, the wireless device interaction process makes it possible for multiple subjects to assess 3D QoE simultaneously in a large space such as a movie theater, at different viewing angles and distances. We conducted a series of interesting 3D experiments showing the accuracy and versatility of the new system, while yielding new findings on visual comfort in terms of disparity, motion and an interesting relation between the naturalness and depth of field (DOF) of a stereo camera.

A Convolutional Neural Network Approach for Objective Video Quality Assessment

This paper describes an application of neural networks in the field of objective measurement method designed to automatically assess the perceived quality of digital videos. This challenging issue aims to emulate human judgment and to replace very complex and time consuming subjective quality assessment. Several metrics have been proposed in literature to tackle this issue. They are based on a general framework that combines different stages, each of them addressing complex problems. The ambition of this paper is not to present a global perfect quality metric but rather to focus on an original way to use neural networks in such a framework in the context of reduced reference (RR) quality metric. Especially, we point out the interest of such a tool for combining features and pooling them in order to compute quality scores. The proposed approach solves some problems inherent to objective metrics that should predict subjective quality score obtained using the single stimulus continuous quality evaluation (SSCQE) method. This latter has been adopted by video quality expert group (VQEG) in its recently finalized reduced referenced and no reference (RRNR-TV) test plan. The originality of such approach compared to previous attempts to use neural networks for quality assessment, relies on the use of a convolutional neural network (CNN) that allows a continuous time scoring of the video. Objective features are extracted on a frame-by-frame basis on both the reference and the distorted sequences; they are derived from a perceptual-based representation and integrated along the temporal axis using a time-delay neural network (TDNN). Experiments conducted on different MPEG-2 videos, with bit rates ranging 2-6 Mb/s, show the effectiveness of the proposed approach to get a plausible model of temporal pooling from the human vision system (HVS) point of view. More specifically, a linear correlation criteria, between objective and subjective scoring, up to 0.92 has been obtained on a set of typical TV videos.

A metric for continuous quality evaluation of compressed video with severe distortions

An objective quality metric that generates continuous estimates of perceived quality for low bit rate video is introduced. The metric is based on a multichannel model of the human visual system. The vision model is initially parameterized to threshold data and then further optimized using video frames containing severe distortions. The proposed metric also discards processing of the finest scales to reduce computational complexity, which also results in an improvement in the accuracy of prediction for the sequences under consideration. A temporal pooling method suited to modeling continuous time waveforms is also introduced. The metric is parameterized and evaluated using the results of a Single Stimulus Continuous Quality Evaluation test conducted for CIF video at rates from 100 to 800 kbps . The proposed metric exceeds the performance of a similar metric based on the Mean Squared Error.

A calibration method for continuous video quality (SSCQE) measurements

It is shown that single stimulus continuous quality evaluation (SSCQE) measurements can be calibrated against a standard reference, even though they relate to long video sequences of up to 25 min duration. This can be accomplished by projecting chosen percentiles in the histogram of continuous quality judgements onto the SSCQE graph, so identifying appropriate representative sections for use in DSCQS tests. Three different algorithms were tested for detailed selection of the 10 s sections, with a modal quality criterion giving the best results. Calibration using both linear and non-linear mapping between SSCQE and MDS scores has been satisfactorily accomplished.

Time Sensitive Evaluation of the Quality of Digitally Coded Sequences

The authors have developed an experimental device suitable for verifying whether assessors can subjectively evaluate temporal variations in picture quality. They also developed a technique suitable for processing opinion scores obtained by means of their device. This new method, the single-stimulus temporally continuous evaluation (SSTCE) method, can solve some problems associated with the single-stimulus continuous quality evaluation (SSCQE) method recommended by the ITU-R, and is more effective for evaluating the time-varying quality of television sequences.

Continuous quality assessment of digitally-coded television pictures

Experimental tests are reported of the use of the ITU-R single-stimulus continuous quality evaluation (SSCQE) method to measure the quality of long (24 min) sequences of digitally coded constant bit-rate video, with and without audio. The results indicate that the method is reliable and free from drift and fatigue effects. The relationship between continuously-judged quality and overall quality judgements, made at the end of the sequences, is shown to be disproportionately influenced by negative SSCQE peaks and relatively little by their duration. The implication of these results for digital television coding and transmission is considered.