Perceptual Impact Research Articles

A Psychophysical Evaluation of Texture Compression Masking Effects

Lossy texture compression is increasingly used to reduce GPU memory and bandwidth consumption. However, as raised by recent studies, evaluating the quality of compressed textures is a difficult problem. Indeed using Peak Signal-to-Noise Ratio (PSNR) on texture images, like done in most applications, may not be a correct way to proceed. In particular, there is evidence that masking effects apply when the texture image is mapped on a surface and combined with other textures (e.g., affecting geometry or normal). These masking effects have to be taken into account when compressing a set of texture maps, in order to have a real understanding of the visual impact of the compression artifacts on the rendered images. In this work, we present the first psychophysical experiment investigating the perceptual impact of texture compression on rendered images. We explore the influence of compression bit rate, light direction, and diffuse and normal map content on the visual impact of artifacts. The collected data reveal huge masking effects from normal map to diffuse map artifacts and vice versa, and reveal the weakness of PSNR applied on individual textures for evaluating compression quality. The results allow us to also analyze the performance and failures of image quality metrics for predicting the visibility of these artifacts. We finally provide some recommendations for evaluating the quality of texture compression and show a practical application to approximating the distortion measured on a rendered 3D shape.

Single-Cell Stimulation in Barrel Cortex Influences Psychophysical Detection Performance.

A single whisker stimulus elicits action potentials in a sparse subset of neurons in somatosensory cortex. The precise contribution of these neurons to the animal's perception of a whisker stimulus is unknown. Here we show that single-cell stimulation in rat barrel cortex of both sexes influences the psychophysical detection of a near-threshold whisker stimulus in a cell type-dependent manner, without affecting false alarm rate. Counterintuitively, stimulation of single fast-spiking putative inhibitory neurons increased detection performance. Single-cell stimulation of putative excitatory neurons failed to change detection performance, except for a small subset of deep-layer neurons that were highly sensitive to whisker stimulation and that had an unexpectedly strong impact on detection performance. These findings indicate that the perceptual impact of excitatory barrel cortical neurons relates to their firing response to whisker stimulation and that strong activity in a single highly sensitive neuron in barrel cortex can already enhance sensory detection. Our data suggest that sensory detection is based on a decoding mechanism that lends a disproportionally large weight to interneurons and to deep-layer neurons showing a strong response to sensory stimulation.SIGNIFICANCE STATEMENT Rat whisker somatosensory cortex contains a variety of neuronal cell types with distinct anatomical and physiological characteristics. How each of these different cell types contribute to the animal's perception of whisker stimuli is unknown. We explored this question by using a powerful electrophysiological stimulation technique that allowed us to target and stimulate single neurons with different sensory response types in whisker cortex. In awake, behaving animals, trained to detect whisker stimulation, only costimulation of single fast-spiking inhibitory neurons or single deep-layer excitatory neurons with strong responses to whisker stimulation enhanced detection performance. Our data demonstrate that single cortical neurons can have measurable impact on the detection of sensory stimuli and suggest a decoding mechanism based on select cell types.

A Detail-Based Method for Linear Full Reference Image Quality Prediction.

In this paper, a novel full Reference method is proposed for image quality assessment, using the combination of two separate metrics to measure the perceptually distinct impact of detail losses and of spurious details. To this purpose, the gradient of the impaired image is locally decomposed as a predicted version of the original gradient, plus a gradient residual. It is assumed that the detail attenuation identifies the detail loss, whereas the gradient residuals describe the spurious details. It turns out that the perceptual impact of detail losses is roughly linear with the loss of the positional Fisher information, while the perceptual impact of the spurious details is roughly proportional to a logarithmic measure of the signal to residual ratio. The affine combination of these two metrics forms a new index strongly correlated with the empirical differential mean opinion score (DMOS) for a significant class of image impairments, as verified for three independent popular databases. The method allowed alignment and merging of DMOS data coming from these different databases to a common DMOS scale by affine transformations. Unexpectedly, the DMOS scale setting is possible by the analysis of a single image affected by additive noise.

First international round robin on auralization: Results of the perceptual evaluation

The round robin on auralization aimed at a systematic evaluation of room acoustic modeling software by means of comparing simulated and measured impulse responses. While a physical evaluation by means room acoustical parameters and spectro-temporal comparisons is addressed in an accompanying talk, here, we focus on an evaluation of perceptual differences arising in complex room acoustical scenarios. In these cases, a mere physical evaluation might not be able to predict the perceptual impact of the manifold interaction of different sound propagation phenomena in enclosed spaces such as reflection, scattering, diffraction, or modal behavior. For this purpose, dynamic auralizations of binaural room impulse responses that were simulated with different room acoustical modeling softwares were evaluated against their measured counterparts. For this purpose, listening tests were conducted using “plausibility” and “authenticity” as overall quality criteria and the Spatial Audio and Quality Inventory (SAQI) for a differential diagnosis of the remaining differences.

Evaluation of the effects of transmission impairments on perceived video quality by exploiting ReTRiEVED dataset

The robust design and adaptation of multimedia networks relies on the study of the influence of potential network impairments on the perceived quality. Video quality may be affected by network impairments, such as delay, jitter, packet loss, and bandwidth, and the perceptual impact of these impairments may vary according to the video content. The effects of packet loss and encoding artifacts on the perceived quality have been widely addressed in the literature. However, the relationship between video content and network impairments on the perceived video quality has not been deeply investigated. A detailed analysis of ReTRiEVED test video dataset, designed by considering a set of potential network impairments, is presented, and the effects of transmission impairments on perceived quality are analyzed. Furthermore, the impact on the perceived quality of the video content in the presence of transmission impairments is studied by using video content descriptors. Finally, the performances of well-known quality metrics are tested on the proposed dataset.

A Study of User Perception of the Quality of Video Content Rendered Inside a 3-D Virtual Environment

This paper reports on the result of a user study to assess the impact of resolution and frame rate of video on the quality of experience of the users, when the video is rendered inside a 3-D virtual space, and consequently viewed from arbitrary perspectives. A mathematical model for video rate is presented that expresses the total rate as the product of separate functions of spatial and temporal resolutions. Results from the user study are combined with the model to predict the rate parameters which will result in perceptually acceptable quality using the 3-D features of the virtual environment. The results show that by exploiting the insensitivity of users to controlled quality degradation, the downstream network load for the client can be significantly reduced with little or no perceptual impact on the clients.

Data Hiding Robust to Mobile Communication Vocoders

The swift growth of cellular mobile networks in recent years has made voice channels almost accessible everywhere. Besides, data hiding has recently attracted significant attention due to its ability to imperceptibly embed side information that can be used for signal enhancement, security improvement, and two-way authentication purposes. In this regard, we aim at proposing efficient schemes for hiding data in the widespread voice channel of cellular networks. To this aim, our first contribution is to model the channel accurately by considering a linear filter plus a nonlinear scaling function. This model is validated through experiments with true speech signals. Then we leverage on this model to propose two additive and multiplicative data hiding methods based on the spread spectrum techniques. In addition, inspired by the concept of M-ary biorthogonal codes, we develop novel schemes that significantly outperform the previous ones. The performance of all the methods that we present is assessed mathematically and cross-validated with simulations. These are later extended to true speech signals where the results evidence an excellent performance as predicted by the theory. Finally, we assess the imperceptibility by means of both subjective and objective benchmarks and show that the perceptual impact of our watermarks is acceptable.

Perceptual Annoyance Models for Videos With Combinations of Spatial and Temporal Artifacts

Understanding the perceptual impact of compression artifacts in video is one of the keys for designing better coding schemes and appropriate visual quality control chains. Although compression and transmission artifacts, such as blockiness, blurriness, and packet-loss, appear simultaneously in digital videos, traditionally they have been studied in isolation. In this paper, we report the results of three subjective quality assessment experiments aimed at studying perceptual characteristics of a set of artifacts common in digital videos. With this goal, first, we study the annoyance of each of three artifacts (blockiness, blurriness, and packet-loss) in isolation and then in combination. Based on the subjective evaluations, we design several models of the annoyance caused by the joint presence of these three artifacts on digital video.

Perceptual attributes for the comparison of head-related transfer functions.

The benefit of using individual head-related transfer functions (HRTFs) in binaural audio is well documented with regards to improving localization precision. However, with the increased use of binaural audio in more complex scene renderings, cognitive studies, and virtual and augmented reality simulations, the perceptual impact of HRTF selection may go beyond simple localization. In this study, the authors develop a list of attributes which qualify the perceived differences between HRTFs, providing a qualitative understanding of the perceptual variance of non-individual binaural renderings. The list of attributes was designed using a Consensus Vocabulary Protocol elicitation method. Participants followed an Individual Vocabulary Protocol elicitation procedure, describing the perceived differences between binaural stimuli based on binauralized extracts of multichannel productions. This was followed by an automated lexical reduction and a series of consensus group meetings during which participants agreed on a list of relevant attributes. Finally, the proposed list of attributes was then evaluated through a listening test, leading to eight valid perceptual attributes for describing the perceptual dimensions affected by HRTF set variations.

Desarrollo de comunidades forestales sustentables en Chihuahua, México

Esta investigación fue enfocada sobre la planeación estratégica participativa para el desarrollo sustentable de comunidades forestales en Chihuahua, México, específicamente en dos ejidos forestales localizados en la Sierra Tarahumara: Basihuare y Cusárare del municipio de Guachochi, Chih. Los objetivos fueron: 1) valorar el manejo actual de los recursos forestales en ambas comunidades, 2) conducir la metodología de la planeación estratégica participativa denominada Conferencia de Búsqueda (CB) para lograr un mejor conocimiento de las necesidades de desarrollo futuro, un cambio positivo de actitud y percepciones y diseñar un plan de acción estratégico para el desarrollo sustentable de la comunidad, y 3) valorar el impacto en las actitudes y percepciones de la gente local en relación con la intervención realizada (CB) para el desarrollo de su comunidad. Los resultados mostraron que: 1) entrevistas etnográficas fueron un complemento fundamental para valorar el enfoque participativo y obtener las opiniones de los miembros de la comunidad sobre el manejo de los recursos forestales y, 2) los residentes de Basihuare, a través de la CB, lograron un mayor conocimiento y conciencia de las necesidades de su desarrollo futuro y se crearon mas cambios positivos en percepciones y actitudes acerca del desarrollo de su comunidad comparado con la gente de Cusárare quien no participó en este proceso de la CB. La CB ayudó a la comunidad de Basihuare a diseñar su propio plan de acción estratégico para lograr un desarrollo sustentable en el futuro y además, debido al proceso democrático y participativo que usaron, ellos llegaron a ser una comunidad planificadora. Finalmente, los resultados sugieren que el estudio puede servir como un modelo para la aplicación del enfoque de sistemas abiertos al desarrollo de comunidades forestales sustentables en la Sierra Tarahumara y en otros lugares más a nivel regional, nacional e internacional.

High Oxygen Delivery to Preserve Exercise Capacity in Patients with Idiopathic Pulmonary Fibrosis Treated with Nintedanib. Methodology of the HOPE-IPF Study.

Pulmonary rehabilitation improves dyspnea and exercise capacity in idiopathic pulmonary fibrosis (IPF); however, it is unknown whether breathing high amounts of oxygen during exercise training leads to further benefits. Herein, we describe the design of the High Oxygen Delivery to Preserve Exercise Capacity in IPF Patients Treated with Nintedanib study (the HOPE-IPF study). The primary objective of this study is to determine the physiological and perceptual impact of breathing high levels of oxygen during exercise training in patients with IPF who are receiving antifibrotic therapy. HOPE-IPF is a two-arm double-blind multicenter randomized placebo-controlled trial of 88 patients with IPF treated with nintedanib. Patients will undergo 8 weeks of three times weekly aerobic cycle exercise training, breathing a hyperoxic gas mixture with a constant fraction of 60% inhaled oxygen, or breathing up to 40% oxygen as required to maintain an oxygen saturation level of at least 88%. End points will be assessed at baseline, postintervention (Week 8), and follow-up (Week 26). The primary analysis will compare the between-group baseline with post-training change in endurance time during constant work rate cycle exercise tests. Additional analyses will evaluate the impact of training with high oxygen delivery on 6-minute walk distance, dyspnea, physical activity, and quality of life. The HOPE-IPF study will lead to a comprehensive understanding of IPF exercise physiology, with the potential to change clinical practice by indicating the need for increased delivery of supplemental oxygen during pulmonary rehabilitation in patients with IPF. Clinical trial registered with www.clinicaltrials.gov (NCT02551068).

Perceptual impact of speech melody hybridization: English and Czech English

The current paper examines the role of intonation in the perception of foreign-accented speech. In order to assess how difficult it is to mentally process native, non-native and modified speech melodies, four conditions were analyzed and compared: native English, native English with Czech melody, Czech English with native melody and Czech English. The method of reaction times measurement in a word monitoring task was employed, in which 108 Czech listeners heard English sentences in the explored conditions and pressed a button when hearing a target word. Speech melody turned out to have a relatively weak but discernible impact on perceptual processing. Interestingly, Czech English proved to be more difficult to process than native English, although the listeners were Czech. The implementation of English F0 contours on Czech English speech slightly alleviated the cognitive load, however, the second hybrid, native English with Czech melody, pointed to the opposite direction. The causes of this discrepancy were investigated, particularly higher degrees of collocability in certain expressions.

Subjective HRTF evaluations for obtaining global similarity metrics of assessors and assessees

In the absence of a well-suited measure for quantifying binaural data variations, this study presents a global perceptual distance metric which can describe both HRTF and listener similarities. The metric is derived based on subjective evaluations of binaural renderings of a sound moving along predefined trajectories on the horizontal and median planes. Its characteristics and advantages in describing data distributions based on perceptually relevant attributes are discussed. In addition, the use of 24 HRTFs from two different databases of origin allows for an evaluation of the perceptual impact of some database-dependent characteristics on binaural spatialization. The effectiveness of the experimental design and the correlation between the HRTF evaluations of the two plane trajectories are also discussed.

When style obscures substance: Visual attention to display appropriateness in the 2012 presidential debates

ABSTRACTAs with the first televised debates in 1960, the 2012 US presidential debates accentuated the importance of nonverbal behavior in political competition, with President Obama receiving widespread criticism for his disengaged and arguably inappropriate communication style in the first debate. To investigate the perceptual impact of such nonverbal expectancy violations, this study first employs an experimental design to examine the consequence of inappropriate leader displays, operationalized as nonverbal behaviors that are incongruent with the rhetorical setting. Theoretical explanations about the evaluative consequences of inappropriate leader displays are described in light of expectancy violations theory. Results of a repeated measures eye-tracking experiment find support for the prediction that inappropriate facial expressions increase visual attention on the source of violation, prompt critical scrutiny, and elicit negative evaluations. These findings are further explored with qualitative analysis of focus group responses to key moments from the first and third presidential debates. The discussion considers the broader implications of nonverbal communication in politics and how expressive leader displays serve as meaningful cues for citizens when making sense of televised political encounters.

Gradient phonemic contrast in Nanjing Mandarin

Sounds that are contrastive in a language are rated by listeners as being more differentfrom each other than sounds that don’t occur in the language or sounds that areallophones of a single phoneme. The study reported in this paper replicates this findingand adds new data on the perceptual impact of learning a language with a new contrast.Two groups of speakers of the Nanjing dialect of Mandarin Chinese were tested. Onegroup was older and had not been required to learn standard Mandarin as school children,while the other younger group had learned standard Mandarin in school. Nanjing dialectdoes not contrast [n] and [l], while standard Mandarin does. Listeners rated the similarityof naturally produced non-words presented in pairs, where the only difference betweenthe tokens was the medial consonant. Pairs contrasting [n] and [l] were rated by olderNanjing speakers as if two [n] tokens or two [l] tokens had been presented, while thesesame pairs were rated by younger Nanjing speakers as noticeably different but not asdifferent as pairs that contrast in their native language.

The Rapid Perceptual Impact of Emotional Distractors.

The brief presentation of an emotional distractor can temporarily impair perception of a subsequent, rapidly presented target, an effect known as emotion-induced blindness (EIB). How rapidly does this impairment unfold? To probe this question, we examined EIB for targets that immediately succeeded (“lag-1”) emotional distractors in a rapid stream of items relative to EIB for targets at later serial positions. Experiments 1 and 2 suggested that emotional distractors interfere with items presented very soon after them, with impaired target perception emerging as early as lag-1. Experiment 3 included an exploratory examination of individual differences, which suggested that EIB onsets more rapidly among participants scoring high in measures linked to negative affect.

Quality of Experience of adaptive video streaming: Investigation in service parameters and subjective quality assessment methodology

The usage of HTTP adaptive streaming (HAS) has become widely spread in multimedia services. Because it allows the service providers to improve the network resource utilization and user׳s Quality of Experience (QoE). Using this technology, the video playback interruption is reduced since the network and server status in addition to capability of user device, all are taken into account by HAS client to adapt the quality to the current condition. Adaptation can be done using different strategies. In order to provide optimal QoE, the perceptual impact of adaptation strategies from point of view of the user should be studied. However, the time-varying video quality due to the adaptation which usually takes place in a long interval introduces a new type of impairment making the subjective evaluation of adaptive streaming system challenging. The contribution of this paper is two-fold: first, it investigates the testing methodology to evaluate HAS QoE by comparing the subjective experimental outcomes obtained from ACR standardized method and a semi-continuous method developed to evaluate the long sequences. In addition, influence of using audiovisual stimuli to evaluate the video-related impairment is inquired. Second, impact of some of the adaptation technical factors including the quality switching amplitude and chunk size in combination with high range of commercial content type is investigated. The results of this study provide a good insight toward achieving appropriate testing method to evaluate HAS QoE, in addition to designing switching strategies with optimal visual quality.

Binaural perception of direct and reverberant sound fields rendered with mixed-order spherical harmonics

Binaural responses can be rendered from a plane-wave decomposition of a measured or a modeled sound field, spatially integrated with free-field head-related transfer functions. When represented in the spherical-harmonics domain, the decomposition order reflects the maximum spatial resolution, which is limited by the number of microphones in the spherical array. Recent studies suggest a direct relationship between decomposition order and perceptual attributes such as localization blur, timbre, and the sense of externalization. Insofar, studies have employed plane wave density functions in which the different components of the sound field were uniformly decomposed at a single spherical-harmonics order. This work is concerned with binaural signals in which the direct and reverberant parts of the sound field are decomposed at different spherical-harmonics orders. The direct component of the sound field carries significant directional information utilized by the auditory system. Therefore, changing the spherical-harmonics order of the direct component is expected to have a different perceptual impact compared to changing the spherical-harmonics order of the reverberant part. Listening experiments are employed to study the perception of such mixed-order representations in context of sound localization and auditory distance perception.

Temporal Video Quality Model Accounting for Variable Frame Delay Distortions

We announce a new video quality model (VQM) that accounts for the perceptual impact of variable frame delays (VFD) in videos with demonstrated top performance on the laboratory for image and video engineering (LIVE) mobile video quality assessment (VQA) database. This model, called VQM_VFD, uses perceptual features extracted from spatial-temporal blocks spanning fixed angular extents and a long edge detection filter. VQM_VFD predicts video quality by measuring multiple frame delays using perception based parameters to track subjective quality over time. In the performance analysis of VQM_VFD, we evaluated its efficacy at predicting human opinions of visual quality. A detailed correlation analysis and statistical hypothesis testing show that VQM_VFD accurately predicts human subjective judgments and substantially outperforms top-performing image quality assessment and VQA models previously tested on the LIVE mobile VQA database. VQM_VFD achieved the best performance on the mobile and tablet studies of the LIVE mobile VQA database for simulated compression, wireless packet-loss, and rate adaptation, but not for temporal dynamics. These results validate the new model and warrant a hard release of the VQM_VFD algorithm. It is freely available for any purpose, commercial, or noncommercial at http://www.its.bldrdoc.gov/vqm/ .

Cortical adaptation and tactile perception.

Cortical neurons reduce spiking responses to repetitive sensory stimulation, but the perceptual impact of this adaptation has been difficult to assess. Work now shows that it has profound consequences for tactile perception.