一种视频质量监测系统的设计与实现

网络服务提供商希望能从用户的角度了解目前网络所提供的服务质量,而用户也希望获得定量的指标来评价当前网络服务质量。为此,以视频质量监测为研究对象,提出一种面向用户体验质量的网络监测系统。通过实验分析了网络传输过程中QoS参数对视频QoE的影响;提出一种将视频流转化为测试序列的视频丢包测量方法,该方法能低入侵、准确测量视频传输过程中的丢包情况;基于以上的研究成果,通过对MIB库的扩展和对MIB库轮询机制的研究,构建了面向QoE的视频服务监测系统,该监测系统结构简单、可行性强,实验表明可实时对网络中的视频服务质量进行监测。     

移动视频业务QoE自适应测量工具

针对不同无线环境（3G、WiFi）下获取用户体验质量（Quality of Experience,QoE）数据困难和不精确的问题,提出一种基于安卓（Android）移动终端视频业务QoE的自适应测量方法.通过实时测量并评估用户在线视频业务体验质量,提高用户体验质量评价的准确性和实用性.为此开发了能自动测量视频QoE的工具,测量服务质量（Quality of Service,QoS）客观参数,通过效用函数映射到主观QoE（MOS值）.通过对理论QoE评价模型（取自文献）与用户实际反馈相关性研究改进理论模型.结果表明,无线环境下改进的模型测量结果更接近用户实际反馈,可以更好地评价QoE.     

Packet loss rate mapped to the quality of experience

In order to study the influence of packet loss on the users’ quality of experience QoE and establish the Mapping model of the two when the video transmit in the network, building a NS2?+?MyEvalvid simulation platform, by the method of modifying QoS parameters to simulate different degrees of packet loss, focus on the influence of packet loss on QoE and establish the mapping model between them. Experimental results show that, packet loss has a significant influence on Quality of experience. Packet loss rate and the Quality of experience presents a nonlinear relationship, and use Matlab to establish the mapping model, this model’s accuracy is high, easy to operate, can real-time detect packet loss has influence on the user’s quality of experience (QoE).     

Subjective and objective quality assessment of videos in error-prone network environments

Compression and transmission are two fundamental stages involved in wireless video communications, each of which may cause degradation of the quality of experience (QoE) of end users by producing compression artifacts and packet loss artifacts, respectively. They have their own unique perceptual influences. To provide insight for designing QoE-aware content delivery applications, this paper studies subjective and objective quality of videos containing both types of artifacts. First, subjective quality assessment is conducted, from which interaction between the two types of artifacts during quality perception is investigated. Second, using the subjective data, the performance of the state-of-the-art objective quality metrics is evaluated, with the aim of examining suitability of the existing metrics for their use in error-prone video communication applications. Finally, the developed data set is made publicly available for the community.     

Impact of video content and transmission impairments on quality of experience

The analysis of the impact of video content and transmission impairments on Quality of Experience (QoE) is a relevant topic for the robust design and adaptation of multimedia infrastructures, services, and applications. The goal of this paper is to study the impact of video content on QoE for different levels of impairments. In more details, this contribution aims at i) the study of the impact of delay, jitter, packet loss, and bandwidth on QoE, ii) the analysis of the impact of video content on QoE, and iii) the evaluation of the relationship between content related parameters (spatial-temporal perceptual information, motion, and data rate) and the QoE for different levels of impairments.     

Bandwidth allocation for video transmission with differentiated quality of experience over wireless networks

Delivering digital video content with enhanced quality of experience to the end users over error-prone multi-hop wireless networks is a challenging issue. In video transmission over such wireless networks, many network-based (packet loss, delay, etc.) and source-based (encoding quantization level etc.) parameters can impose some levels of impairment on the perceived video quality. In a video quality enhancement strategy, accurate video quality metrics play a crucial role in the designing process of optimal rate (bandwidth) allocation algorithms. Many cross-layer optimization (CLO) based rate allocation strategies have been developed for this purpose which consider different objective functions (congestion level, total packet loss, etc.) in wireless networks. The main contributions of the proposed work are twofold. At first, an optimal bandwidth allocation framework is being developed in which based on some network-specific constraints and by incorporating an accurate video quality metric, the total weighted quality of experience of some competing video sources is being optimized bases on cross-layer design techniques. Secondly, these optimal rates have been used for differentiated Quality of Experience (QoE) enforcement between multiple competing video sources. The resulting optimal rates can be used as rate-feedbacks for on-line rate adaptation of a moderate video encoder such as MPEG4. The aforementioned weight parameters are selected based on the importance of each video sequence’s quality and can be associated with some previous service level agreement (SLA) based prices. Some numerical analysis have been presented to validate the theoretical results and to verify the claims.     

丢包对视频体验质量影响的分析

网络传输过程中发生丢包会降低用户对视频的体验质量。使用EvalVid仿真传输测试床来深入分析丢包率及不同位置丢包对用户体验的影响,并根据回归分析法建立了映射模型。用户使用该模型可以很方便地得出用户的体验质量。经理论分析证明该模型正确、易于操作,可实时检测丢包对视频的影响。     

移动互联网下视频时延的用户体验质量研究

随着移动互联网的发展,移动视频业务的迅速爆发,良好的用户体验质量(QoE) 成为运营商挽留用户的关键因素。从用户体验角度,建立不同时延下移动视频业务的评价量化 标准。通过情景实验模拟的方法,以平均主观意见分(mean opinion score,MOS)量表建立用户 视频体验质量的实数映射关系。针对用户对视频观看时延的有效反应进行分级研究,得到以下 结果：单次和多次的初始缓冲时延和卡顿时延对用户观看移动视频的影响并建立用户体验质量 评价等级。在短视频中出现单次时延在4 s 以上,用户会出现负面情绪;在相同延迟时长下, 单次的初始缓冲时延的用户体验质量略优于卡顿时延;对于在一定播放时长的移动视频业务中 出现多次卡顿,卡顿时延短但是间隔频繁的体验质量比卡顿时延长但是间隔时间长的体验质量 要更差。     

User perception of adapting video quality

In general, video quality adaptation and video quality evaluation are distinct activities. Most adaptive delivery mechanisms for streaming multimedia content do not explicitly consider user-perceived quality when making adaptation decisions. Equally, video quality evaluation techniques are not designed to evaluate instantaneous quality where the quality is changing over time. We propose that an Optimal Adaptation Trajectory (OAT) through the set of possible encoding exists, and that it indicates how to adapt encoding quality in response to changes in network conditions in order to maximize user-perceived quality. The subjective and objective tests carried out to find such trajectories for a number of different MPEG-4 video clips are described. Experimental subjective testing results are presented that demonstrate the dynamic nature of user perception with adapting multimedia. The results demonstrate that adaptation using the OAT out-performs conventional adaptation strategies in which only a single aspect of the video quality is adapted. In contrast, the OAT provides a mechanism to adapt multiple aspects of the video quality thereby giving better user-perceived quality in both the short and long term.     

丢包对音频流体验质量的影响分析

分组网络中丢包对音频流媒体用户体验具有显著影响,为了深入分析两者间的相关性,设计了丢包可控的多媒体仿真传输实验平台,采用回归分析,建立了编码方式、RTP分组间隔等多因素限定下丢包率与体验质量间的映射模型。该模型计算复杂度低,可实时预测丢包对体验质量的损害。     

QoE assessment model for multimedia streaming services using QoS parameters

This paper proposes a video QoE (Quality of Experience) assessment model which can assess video quality of experience with only QoS (Quality of Service) parameters and their relative importance at network layer. Since network or service providers can forecast whether to provide multimedia services above a certain level of service quality using the proposed model, they can offer and maintain optimum network environment for multimedia service such as IPTV. Through an experiment of video quality comparison we show that our QoS/QoE correlation model is closely related with video quality degradation patterns to network environmental change.     

An ANFIS model of quality of experience prediction in education

This paper presents a Quality of Experience (QoE) prediction model in a student-centered blended learning environment, equipped with appropriate technologically enriched classroom. The model uses ANFIS technique to infer the QoE from the individual subjective factors and the objective technical factors which altogether influence the perceived QoE. We explored the influence of subjective personality traits extroversion and neuroticism, as well as the learning style on QoE. The objective factors included in the model are technically measurable parameters latency, jitter, packet loss and bandwidth affecting Quality of Service (QoS) of the underlying technology. The findings presented in this paper are obtained from a case study which involved 8 teachers and 142 students from second and sixth grade in five primary schools in the Republic of Macedonia. The teachers involved in the project introduced game-based learning strategies in classes, including on-line videoconferences, streamed video content and classical face to face gaming. We constructed three ANFIS systems with seven and four input variables and compared their performances using the RMSE, MAPE and R² measurements. The results showed that perceived QoE can be reliably predicted by the student's personality traits and learning style as subjective factors and network jitter as an objective factor.     

Compressed-domain-based no-reference video quality assessment model considering fast motion and scene change

Due to the variability of wireless channel state, video quality monitoring became very important for guaranteeing users’ Quality of Experience (QoE). QoE presents the overall perceptual quality of service from the subjective users’ perspective. However, because of diverse characteristics of video content, Human Visual System (HVS) cannot give the same attention to whole scene simultaneously when facing video sequence. In this paper, we proposed a video quality assessment model by considering the influence of fast motion and scene change. The motion change contribution factor and scene change contribution factor are defined to quantify the characteristics of video content, which is closely related to the users’ QoE. Based on G.1070, our proposed model considers the influential factors of loss nature of video coding, variability of practical network and video features. Also, the proposed model owns low computational complexity due to the compressed domain approach for the estimation of the model parameters. Therefore, the video quality is assessed without fully decoding the video stream. The performance of our proposed model has been compared with five existing models and the results also shown that our model has high prediction accuracy closing to human perception.     

运动感知基于缓存的自适应视频流传输

目的 基于缓存的自适应视频流传输策略无需估测实时带宽,直接通过缓存变化量与码率的映射函数选取符合当前网络状况的最佳质量码流传输。传统基于缓存的自适应视频传输不考虑内容特征,在码率选择上为不同运动级别视频内容均使用相同的码率映射函数,在不稳定的无线网络环境中高运动强度内容的码率急剧降低会严重伤害用户体验质量（QoE）,提出运动感知基于缓存的自适应视频流传输（MA-BBA）算法。方法 MA-BBA算法根据片段运动级别确定码率映射函数,对运动强度高的内容快速切换到较高码率,而对于运动强度较低的内容则使用较为保守的码率,从而使得缓存资源能够位于安全边界之上且较多分配给高级别运动内容,提高不同运动强度内容的平均质量,使整体QoE得到优化。结果 在公开的无线网络带宽数据集上实现本文MA-BBA算法,基于吞吐量的自适应传输算法（TBA）和基于缓存的自适应传输算法（BBA）。MA-BBA在高运动强度内容的平均质量上比TBA和BBA分别提高1.7%和1.2%,且质量波动区间更小。MA-BBA在平均缓存利用率上达到72%,大大高于TBA的45.9%和BBA的45.4%。结论 MA-BBA算法与现有的码率自适应算法TBA和BBA相比,大大提高了缓存资源利用率,提高了对资源要求最苛刻的高级别运动内容的传输质量,减小码率切换幅度频率,优化了视频服务的整体QoE。     

Evaluation and monitoring of video quality for UMA enabled video streaming systems

This paper deals with monitoring user perception of multimedia presentations in a Universal Multimedia Access (UMA) enabled system using objective no-reference (NR) metrics. These NR metrics are designed for an UMA-enabled system, in a novel architecture, for a multimedia viewer. The first metric measures block-edge impairments in a video frame at the receiver end, based on the observation that they occur in regions with low spatial activity. The second metric evaluates the quality of the reconstructed video frame in the event of packet loss. Here, the structure of the artifact is itself exploited for the evaluation. Both the metrics involve low computational complexity and are feasible for real-time monitoring of streaming video in a multimedia communication scenario. Further, in rate-adaptive streaming of video, these metrics could serve as feedback parameters to dynamically adapt the bit rates based on network congestion.

Not All Packets Are Equal, Part I: Streaming Video Coding and SLA Requirements

In this first part of a two-part article, the authors consider the network factors that impact the viewers' quality of experience (QoE) for IP-based video-streaming services such as IPTV. They describe the IP service-level requirements for a transported video service and explain MPEG encoding to help readers better understand the impact that packet loss has on viewers' QoE.     

A holistic approach for personalization,relevance feedback & recommendation in enriched multimedia content

As the prerequisites of production houses, broadcasters, advertising agencies and online publishing companies for enriched multimedia content increase rapidly, the need of innovative methods for the effective creation of enriched multimedia content is undeniable. Stemming from this need, in this paper we focus on the design, development and evaluation of a framework consisting of personalization, relevance feedback and recommendation mechanisms, as a principal method for the creation of enriched multimedia content targeted to each user’s needs, preferences and interests. As the multimedia content proliferates along with its consumption by the users, more effective ways of presenting it to the viewers are demanded in order to facilitate them with the multimedia content search and selection and improve their Quality of Experience (QoE). The main contribution of the paper is the introduction of a holistic framework that offers personalized enriched multimedia content, by extending the recommendation process to the set of enrichments that accompany the video except from the video itself and by collecting explicit and implicit relevance feedback from the interactions of the user with both the video and its enrichments. We evaluate the proposed framework following a two-step approach. Firstly, we perform extended experiments by applying reasonably simulated user interactions, in order to calibrate its parameters that refer to multiple aspects of the enriched multimedia content, aiming at high performance in terms of QoE. Here, most importantly, we have shown that appropriately designing the enrichments and considering users’ interactions with them allows for achieving a better quality in inferring users’ profiles in many realistic cases. Secondly, we integrated our proposed recommender framework within the MECANEX streaming platform in order to perform user studies about its usability within a realistic environment of use.     

基于随机森林的带宽预测算法研究与实现

为解决手机移动端带宽波动导致用户视频服务体验降低的问题,提出一种移动手机可用带宽预测算法(mobile available bandwidth prediction,MABP)。采集Android手机的LTE参数,使用随机森林预测手机带宽,当客户端发起视频服务请求时,同时向服务器反馈手机的当前可用带宽,服务器根据移动客户端提供的带宽信息进行自适应流分发(发送最优码率的视频),降低视频画面卡顿、画质模糊、切换时间过长等问题,提升用户体验(quality of experience,QoE)。在实际的网络环境下验证了所述算法的有效性。