Subjective Video Quality Evaluation Research Articles

A Hybrid QoS-QoE Estimation System for IPTV Service

The internet protocol television service (IPTV) has become a key product for internet service providers (ISP), offering several benefits to both ISP and end-users. Because packet networks based on internet protocol have not been prepared for time-sensitive services, such as voice or video, packet networks have had to adopt several mechanisms to secure minimal transmission standards in the form of data stream prioritization. There are two commonly used approaches for video quality assessment. The first approach needs an original source for comparison (full-reference objective metrics), and the second one requires observers for subjective evaluation of video quality. Both approaches are impractical in real-time transmission because it is difficult to transform an objective score into a subjective quality perception, and on the other hand, subjective tests are not able to be performed immediately. Since many countries worldwide put IPTV on the same level as other broadcasting systems (e.g., terrestrial, cable, or satellite), IPTV services are subject to regulation by the national regulation authority. This results in the need to prepare service qualitative criteria and monitoring tools capable of measuring end-user satisfaction levels. Our proposed model combines the principles of both assessment approaches, which results in an effective monitoring solution. Therefore, the main contribution of the created system is to offer a monitoring tool able to analyze the features extracted from the video sequence and transmission system and promptly translate their impact into a subjective point of view.

Semantic label bias in subjective video quality evaluation: a standardization perspective

Recent studies brought to light that the semantic labels (e.g. Excellent, Good, Fair, Poor, and Bad) commonly associated with discrete scale ITU subjective quality evaluation induce a bias in MOS computation and that such a bias can be quantified by some reference coefficients which are independent with respect to the observers panel. The present paper reconsiders these results from a standard upgrading perspective. First, it theoretically investigates the way in which results obtained on semantically labeled scales can be “cleaned” from such an influence and derives the underlying computation formula for the mean opinion score. Secondly, it suggests a unitary evaluation procedure featuring both semantic free MOS computation and backward compatibility with respect to state-of-the-art solutions. The theoretical and methodological results are supported by subjective experiments corresponding to a total of 440 human observers, alternatively scoring 2D and stereoscopic video content. For each type of content, both high and low quality excerpts are alternatively considered. For each type of content and for each type of quality a 5 level (Excellent, Good, Fair, Poor, and Bad) grading scales is considered.

Subjective Video Quality Evaluation and User Satisfaction according to Screen Size and Content Type: Comparison of UHD and UWV

Subjective Video Quality Evaluation and User Satisfaction according to Screen Size and Content Type: Comparison of UHD and UWV

Do gaze disruptions indicate the perceived quality of non-uniformly coded natural scenes?

Subjective video quality evaluation techniques usually involves a subject voluntarily attending to several regions in a video in order to scrutinize its quality. These techniques often tend to over-estimate the visual thresholds and in cases of non-uniform quality/coding, subjects mostly perceive the underlying video content in worse quality. This occurs due to a process known as Attentional Modulation occurring in the higher visual cortical areas V2 to V4. Examining disruptions in free viewing gaze patterns on the other hand, are said to be a more naturalistic method to measure the perceived video quality in such cases. To explore the feasibility of such a gaze disruption based quality metric, we examine the dependency between the two indicators: gaze disruptions and perceived subjective quality, obtained from a carefully controlled subjective test. By the examination of eye-tracking data and subsequent statistical analysis of difference opinion scores given by users, we are able to see that disruptions are indeed excellent indicators of perceived quality achieving a correlation 0.84. Several state of the art objective video quality metrics like SSIM, VIFp, VQM and PSNR-HVS (designed mostly for evaluation of uniform-quality) on the other hand, only produce a correlation ranging from 0.01 to 0.10. We conclude therefore that gaze disruptions may be used as excellent natural indicators of perceived quality in cases where quality is non-uniform, and may serve as new ground truth indicators for objective algorithms like Scanpath disruption(prediction) metrics that measure video quality in a more real-world like(naturalistic) manner.

Subjective video quality evaluation of different content types under different impairments

ABSTRACTNowadays, access to multimedia content is one of the most demanded services on the Internet. However, the transmission of audio and video over these networks is not free of problems that negatively affect user experience. Factors such as low image quality, cuts during playback or losses of audio or video, among others, can occur and there is no clear idea about the level of distortion introduced in the perceived quality. For that reason, different impairments should be evaluated based on user opinions, with the aim of analyzing the impact in the perceived quality. In this work, we carried out a subjective evaluation of different types of impairments with different types of contents, including news, cartoons, sports and action movies. A total of 100 individuals, between the ages of 20 and 68, participated in the subjective study. Results show that short-term rebuffering events negatively affect the quality of experience and that desynchronization between audio and video is the least annoying impairment. Moreover, we found that the content type determines the subjective results according to the impairment present during the playback.

Quality analysis of real-time digital broadcasting images applying the Qoe measurement technology

For the subjective measurement of video quality, various standard methods are suggested, but these are based on short-time video watching (around 10 s) under the condition that the original standard video exists. In the digital broadcasting (IPTV, DCATV, satellite broadcasting) watching conditions, however, people watch videos for a long time, rendering the 10-s measurement inadequate in real life. In this paper, the effect of the evaluation cycle on the "mean opinion score" is analyzed, and a method of selecting an appropriate evaluation cycle for the subjective video quality evaluation of digital broadcasting is proposed. In addition, the real-time video quality of local commercial broadcasting services is measured by applying evaluation types, and the measurements are analyzed.

Intelligibility Threshold for Cued Speech in H.264 Video Conference

Intelligibility Threshold for Cued Speech in H.264 Video Conference This paper discusses the cued speech recognition methods in videoconference. Cued speech is a specific gesture language that is used for communication between deaf people. We define the criteria for sentence intelligibility according to answers of testing subjects (deaf people). In our tests we use 30 sample videos coded by H.264 codec with various bit-rates and various speed of cued speech. Additionally, we define the criteria for consonant sign recognizability in single-handed finger alphabet (dactyl) analogically to acoustics. We use another 12 sample videos coded by H.264 codec with various bit-rates in four different video formats. To interpret the results we apply the standard scale for subjective video quality evaluation and the percentual evaluation of intelligibility as in acoustics. From the results we construct the minimum coded bit-rate recommendations for every spatial resolution.

DTV 분산중계망 필드 테스트 결과

분산중계 방식은 기존 중계기를 이용하는 MFN(Multiple Frequency Network)과 OCR(On Channel Repeater)을 이용한 SFN(Single Frequency Network)에 비해 기존의 송출시설을 최대한 활용할 수 있고, 짧은 시간에 구축이 가능하여 비용이 효율적이며, 주파수 이용 효율을 높일 수 있는 방식이다. 본 필드 테스트는 이러한 분산중계 방식의 성능을 검증하고자 서울 서북부 지역을 중심으로 3세대, 5세대 그리고 6세대 수신기를 이용하여 총 30개 지점에 대하여 수신 전계강도와 노이즈마진 및 수신가능각을 측정하였고, 수신화질의 주관적 평가를 수행하였다. 필드 테스트를 수행한 결과 모든 조건의 수신기에서 수신 성능의 향상을 보였다. 각 수신기별 특성을 볼 때 3세대 수신기에 비해 5세대 수신기 및 6세대 수상기는 수신율의 향상뿐만 아니라 수신가능각도 증가되어 분산중계망의 가능성을 알 수 있었다. A Distributed Translator Network(DTxR) is a cost-effective and frequency-effective method which can use existing transmission utilities and can be constructed in a shorter time as compared with Multiple Frequency Network(MFN) or Single Frequency Network(SFN) using On Channel Repeater(OCR). In order to verify the feasibility of DTxR, this field test was done in 30 points of north-west area in Seoul using 3rd, 5th, and 6th generation DIV receivers. Electric field strength, noise margin and ease of reception were measured and subjective evaluation of video quality was done in these points during the field test. With the test result, an improvement of receiving quality was obtained and an ease of reception was increased in case of the 5th. and 6th. receiver. From the results, we conclude that DTxR is a feasible method in DIV networks.