Video Quality Metrics Research Articles

Vers une métrique de description objective d'une sensation subjective

In the last decade, several image and video quality metrics have been proposed, which incorporate perceptual quality measures by considering the HVS characteristics. All this metrics do the differences pixel to pixel in image. Therefore a local fidelity of the colour is defined. However, the human visual system is rather sensitive to a global quality. In this paper, we propose a new objective full reference quality metric for colour images called Global Delta E and noted: ~ G DE . This metric is based on human visual system properties in order to obtain the best correspondence with judgments. Some experimentations and assessments prove the performance of our metrics and that interrelationship with the SVH. L'étude du système visuel Humain (SVH) est primordiale pour quantifier la qualité d'une image. Plusieurs travaux ont proposé des métriques de différences de couleurs qui effectuent des différences locales pixel par pixel. Par contre, le système visuel humain est plutôt sensible à une qualité globale. Dans cet article, nous proposons une nouvelle métrique objective de différence couleur basée sur les caractéristiques du système visuel humain. La métrique proposé est appelée Delta E Globale notée : ~ DEG . Quelques expérimentations et évaluations montrent la performance de cette métrique et sa corrélation avec la vision du SVH.

VQeg validation and ITU standardization of objective perceptual video quality metrics [Standards in a Nutshell

For industry, the need to access accurate and reliable objective video metrics has become more pressing with the advent of new video applications and services such as mobile broadcasting, Internet video, and Internet Protocol television (IPTV). Industry-class objective quality- measurement models have a wide range of uses, including equipment testing (e.g., codec evaluation), transmission- planning and network-dimensioning tasks, head-end quality assurance, in- service network monitoring, and client-based quality measurement. The Video Quality Experts Group (VQEG) is the primary forum for validation testing of objective perceptual quality models. The work of VQEG has resulted in International Telecommunication Union (ITU) standardization of objective quality models designed for standard- definition television and for multimedia applications. This article reviews VQEG's work, paying particular attention to the group's approach to validation testing.

Rule-Based No-Reference Video Quality Evaluation Using Additionally Coded Videos

This contribution presents a no-reference video quality metric, which is based on a set of simple rules that assigns a given video to one of four different content classes. The four content classes distinguish between video sequences which are coded with a very low data rate, which are sensitive to blocking effects, which are sensitive to blurring, and a general model for all other types of video sequences. The appropriate class for a given video sequence is selected based on the evaluation of feature values of an additional low-quality version of the given video, which is generated by encoding. The visual quality for a video sequence is estimated using a set of features, which includes measures for the blockiness, the blurriness, the spatial activity, and a set of additional continuity features. The way these features are combined to compute one overall quality value is determined by the feature class, to which the video has been assigned. We also propose an additional correction step for the visual quality value. The proposed metric is verified in a process, which includes visual quality values originating from subjective quality tests in combination with a cross validation approach. The presented metric significantly outperforms peak-signal-to-noise ratio as a visual quality estimator. The Pearson correlation between the estimated visual quality values and the subjective test results takes on values as high as 0.82.

A Novel Video Quality Metric for Low Bit-Rate Video Considering Both Coding and Packet-Loss Artifacts

This paper investigates the perceptual quality of video affected by packet losses. We focus on low-resolution and low bit-rate video coded by the H.264/AVC encoder and the packet loss patterns likely in low bit-rate wireless networks. We examine the impact of several factors on the perceptual quality, including the error length (the error propagation duration after a loss), the loss severity (measured by the pixel difference between reference and distorted video in the area affected by a loss), loss location, the number of losses, and loss patterns. Based on our findings, we propose an objective metric for the quality degradation due to packet losses that considers all these factors. We also validate a prior metric relating the quality degradation due to compression artifacts and the peak-signal-to-noise ratio (PSNR). We finally propose a full-reference metric that measures the overall quality degradation due to both packet losses and lossy compression. The proposed metric correlates very well with subjective ratings, for a large set of video clips with different loss patterns, coding artifacts, and scene contents.

Rate controlling in off line 3D video coding using evolution strategy

In this paper, we propose a rate control technique for 3D video using subjective quality for off line video coding. We propose to use Video Quality Metric (VQM) with an evolution strategy (ES) algorithm, which is capable of identifying the best possible quantization parameters for each 16times16 macroblock, of both colour and depth map videos, to encode the 3D sequence such that it would maximize the subjective quality of the entire video sequence subjected to the target bit rate. Simulation results suggest that the proposed technique can improve the RD performance of the H.264/AVC codec significantly. With the proposed technique, up to 35% bit rate reduction can be achieved at the same video quality. Furthermore, results show that the proposed technique can improve the subjective quality of the encoded video significantly for video sequences especially with high motion.

Modeling RPS and Evaluating Video Repair With VQM

Reference picture selection (RPS) is a promising repair technique in lossy networks for delay-sensitive video, whereby the video encoder uses one of several previous frames as a reference frame for predictive encoding. RPS can operate in two different modes: an optimistic policy that uses negative acknowledgements (NACKs) and a more conservative policy that relies upon positive acknowledgements (ACKs). This paper compares RPS NACK and RPS ACK under various network conditions and video contents using two analytical models. The two models characterize RPS NACK and RPS ACK by incorporating the impact of reference distance on video quality, prediction dependency among video frames and Group of Pictures (GOP) length. Given packet-loss rate, round-trip time and capacity constraints, the models predict average video quality for videos with RPS ACK and RPS NACK using the Video Quality Metric (VQM). Using these two models, a series of experiments are conducted to investigate RPS performance under various conditions. The insights derived from our models can help determine appropriate choices for RPS NACK and RPS ACK under various network conditions and video contents.

Evolution strategy based rate controlling for off-line video coding

An intelligent rate control technique for H.264/AVC using the subjective quality of video is proposed. A subjective video quality metric is used with an evolution strategy algorithm, which is capable of identifying the best possible quantisation parameters for each frame/macroblock to encode the video sequence such that it would maximise the subjective quality of the entire video sequence subjected to the target bit rate. Simulation results show that up to 40% bit rate saving can be achieved with the proposed technique at the same video quality.

Rate Controlling in H.264/AVC Using Subjective Quality of Video and Evolution Strategy

In this paper, we propose a rate control technique for H.264/AVC using subjective quality of video for off line video coding. We propose to use Video Quality Metric (VQM) with an evolution strategy algorithm, which is capable of identifying the best possible quantization parameters for each frame/macroblock to encode the video sequence such that it would maximize the subjective quality of the entire video sequence subjected to the target bit rate. Simulation results suggest that the proposed technique can improve the RD performance of the H.264/AVC codec significantly. With the proposed technique, up to 40% bit rate reduction can be achieved at the same video quality. Furthermore, results show that the proposed technique can improve the subjective quality of the encoded video significantly for video sequences especially with high motion.

A rate control technique for off line H.264/AVC video coding using subjective quality of video

In this paper, we propose a rate control technique for H.264/AVC using subjective quality of video for off line video coding. We propose to use video quality metric (VQM) with an evolution strategy algorithm, which is capable of identifying the best possible quantization parameters for each frame to encode the video sequence such that it would maximize the subjective quality of the entire video sequence subjected to the target bit rate. Simulation results suggest that the proposed technique can improve the RD performance of the H.264/AVC codec significantly. With the proposed technique, up to 35% bit rate reduction can be achieved at the same video quality. Furthermore, results show that the proposed technique can improve the subjective quality of the encoded video significantly for video sequences especially with high motion.

IPTV 서비스 영상에 대한 객관적 품질측정 방안 연구

최근 IP 기반의 멀티미디어 서비스가 증가하면서 IPTV에 대한 수요가 급증할 것으로 예상되고 있다. IPTV는 케이블을 이용하는 기존의 TV와 달리 IP 네트워크 기반의 다양한 서비스 제공이 가능하다. 그러나 IPTV 서비스 품질은 패킷 손실, 지터와 같은 네트워크 열화에 크게 영향을 받기 때문에 언제나 안정된 서비스를 보장하기가 힘들다. 본 논문에서는 다양한 영상 열화에 대하여 주관적 평가를 반영한 IPTV 서비스 품질측정 방안을 도출한다. 이를 위하여 시청자에게 인지적으로 영향을 줄 수 있는 열화 항목을 선정하였으며 선정된 각 열화 항목에 대하여 측정 메트릭을 제안하였다. 각 열화 항목에 대하여 MOS(Mean Opinion Score) 기반의 주관적 평가를 수행하였으며 제안한 메트릭의 측정 결과를 주관적 평가에 사상시켜 주관적 인지 상태를 고려하는 항목별 객관적 품질측정 기준을 도출한다. 다양한 영상에 대한 실험을 통해 개발된 품질측정 메트릭이 주관적 측면을 잘 반영하고 있음을 확인할 수 있다. With the advent of IP-based multimedia service based on IP network, there is a rapidly increasing demand for IPTV. Unlike the previous coaxial cable based TV, IPTV provides a variety of convergence services based on IP newark. However, since the IPTV service quality is a lot affected by the network degradation such as packet loss and jitter, it may not be guaranteed. In this paper, we propose an objective measure for various degradations of IPTV-based videos considering subjective assessment. To this end, we first determine QoE(Quality of Experience) indicators, which can affect human visual perception. Then we develop the video quality metric for each QoE indicator. Subjective assessment based on MOS is conducted and used to construct mapping relationship between each measure and perceived visual quality. Experiments are performed on various videos to confirm the efficiency and robustness of the proposed method and show high correlation with subjective assessment.

ARMOR – A system for adjusting repair and media scaling for video streaming

To optimize scarce network resources and present the highest quality video, streaming video systems need adapt to the video content as well as the network conditions. This paper presents ARMOR, a video streaming system that dynamically adjusts repair and media scaling to meet current video and network conditions. In order to adapt effectively, ARMOR, and any dynamic video adaptation system, needs to predict the video quality as perceived by end users over the range of scaling and repair choices. Thus, this paper first proposes a novel video quality metric called distorted playable frame rate that provides estimation of user perceptual quality considering temporal and quality degradations. Comprehensive user studies show distorted playable frame rate is more accurate than other video quality metrics. Analytic experiments with distorted playable frame rate and the ARMOR optimization algorithm illustrate the predictive power of the metric in a dynamic, streaming video system. Lastly, implementation and experiments of a complete, fully-functioning ARMOR system show the effective practicality of the proposed approach.

Objective video quality measure for application to tele-echocardiography

Real-time tele-echocardiography is widely used to remotely diagnose or exclude congenital heart defects. Cost effective technical implementation is realised using low-bandwidth transmission systems and lossy compression (videoconferencing) schemes. In our study, DICOM video sequences were converted to common multimedia formats, which were then, compressed using three lossy compression algorithms. We then applied a digital (multimedia) video quality metric (VQM) to determine objectively a value for degradation due to compression. Three levels of compression were simulated by varying system bandwidth and compared to a subjective assessment of video clip quality by three paediatric cardiologists with more than 5 years of experience.

A Cross-Layer Approach for Maximizing Visual Entropy Using Closed-Loop Downlink MIMO

We propose an adaptive video transmission scheme to achieve unequal error protection in a closed loop multiple input multiple output (MIMO) system for wavelet-based video coding. In this scheme, visual entropy is employed as a video quality metric in agreement with the human visual system (HVS), and the associated visual weight is used to obtain a set of optimal powers in the MIMO system for maximizing the visual quality of the reconstructed video. For ease of cross-layer optimization, the video sequence is divided into several streams, and the visual importance of each stream is quantified using the visual weight. Moreover, an adaptive load balance control, named equal termination scheduling (ETS), is proposed to improve the throughput of visually important data with higher priority. An optimal solution for power allocation is derived as a closed form using a Lagrangian relaxation method. In the simulation results, a highly improved visual quality is demonstrated in the reconstructed video via the cross-layer approach by means of visual entropy.

Meet In the Middle Cross-Layer Adaptation for Audiovisual Content Delivery

This paper describes a new architecture and implementation of an adaptive streaming system (e.g., television over IP, video on demand) based on cross-layer interactions. At the center of the proposed architecture is the meet in the middle concept involving both bottom-up and top-down cross layer interactions. Each streaming session is entirely controlled at the RTP layer where we maintain a rich context that centralizes the collection of (i) instantaneous network conditions measured at the underlying layers (i.e.: link, network, and transport layers) and (ii) user- and terminal-triggered events that impose new real-time QoS adaptation strategies. Thus, each active multimedia session is tied to a broad range of parameters, which enable it to coordinate the QoS adaptation throughout the protocol layers and thus eliminating the overhead and preventing counter-productiveness among separate mechanisms implemented at different layers. The MPEG-21 framework is used to provide a common support for implementing and managing the end-to-end QoS of audio/video streams. Performance evaluations using peak signal to noise ratio (PSNR) and structural similarity index (SSIM) objective video quality metrics show the benefits of using the proposed Meet In the Middle cross-layer design compared to traditional media delivery approaches.

Scope of validity of PSNR in image/video quality assessment

Experimental data are presented that clearly demonstrate the scope of application of peak signal-to-noise ratio (PSNR) as a video quality metric. It is shown that as long as the video content and the codec type are not changed, PSNR is a valid quality measure. However, when the content is changed, correlation between subjective quality and PSNR is highly reduced. Hence PSNR cannot be a reliable method for assessing the video quality across different video contents.

Estimation of the peak signal-to-noise ratio for compressed video based on generalized Gaussian modeling

The peak signal-to-noise ratio (PSNR) is one of the most popular video quality metrics. This ratio is computed using both original and processed images. We propose a new method to estimate the PSNR from an encoded bit stream without using original video sequences. In the proposed method, the transform coefficients of images or video frames are modeled by a generalized Gaussian distribution. By utilizing the model parameters of this distribution, the PSNR can be estimated. We also propose a fast method that can be used to estimate the model parameters of the original transform coefficient distribution using quantized transform coefficients as well as quantization information extracted from encoded bit streams. Experimental results with H.264 bit streams show that the proposed generalized Gaussian modeling method delivers better performance compared to the standard Laplacian modeling method when estimating the PSNR. The proposed method can be applied to image or video streams compressed with standard coding algorithms, such as MPEG-1, 2, 4, H.264, and JPEG. The proposed method can also be used for image or video quality monitoring systems on the receiver's side.

Video Quality Metric for Bit Rate Control via Joint Adjustment of Quantization and Frame Rate

The purpose of this study is to propose a quality metric of video encoded with variable frame rates and quantization parameters suitable for mobile video broadcasting applications. As a first step, experiments are conducted to assess the subjective quality of video sequences encoded with variable frame rates and quantization parameters. Resulting experimental data show that for the purpose of video rate control, optimization using the classical PSNR does not match up to that of subjective quality data. The second step bridges this gap between PSNR and subjective quality data by constructing a new quality metric that accounts for both encoding parameters (quantization and frame rate), and intrinsic video sequence characteristics (motion speed). The average correlation coefficient for five video sequences tested is as high as 0.93 with the proposed metric, in contrast with the PSNR's 0.70

QoS assessment of 3G video-phone calls by tracing watermarking exploiting the new colour space ‘YST’

Tracing watermarking has been recently proposed as a technique to provide a blind measure of the quality of service of the communication link, focusing on multimedia communication scenarios. 3G communication scenarios, where each customer transmits both voice and MPEG-4 video sequences in real time, have been considered. Typical video-phone call consists of close shots of speakers, framing their face in the foreground. For such particular application, a novel colour space (YST) is adopted to minimise the perceptual distortions on face coding introduced by watermarking. In the YST space, the luminance component (Y) is the same as in conventional YUV space, whereas the vectors S and T lie within the chrominance (UV) plane. The S (skin) component is a linear combination of U and V obtained as the ‘average’ chrominance estimated from an assorted set human faces to achieve a reasonable generalisation. The third component, T, is defined as orthogonal to the YS plane. The results show the benefits obtained in digital watermarking by the new representation against the conventional approach. In fact, the sensitivity of the YST representation outperforms the conventional one in terms of objective (mean square error, peak signal-to-noise ratio) and subjective (video-quality metrics) indicators.

Delivering audiovisual content with MPEG-21-enabled cross-layer QoS adaptation

Future multimedia communication systems have to support the user's needs, the terminal capabilities, the content specification and the underlying networking technologies. The related protocols and applications must be designed from this integration perspective in a cross-layer centric manner. In this paper, we propose an implementation of a streaming service (e.g., Television over IP service) with a unified QoS management concept that enables an IP driven integration of different system components (terminal, user, content, and network). The MPEG-21 framework is used to provide a common support for imple- menting and managing the end-to-end QoS. The main focus of this paper is on the architecture design, protocols specification and implementation evaluation. Performance evaluations using PSNR and SSIM objective video quality metrics show the benefit of the proposed MPEG-21-enabled cross-layer adaptation.

Understanding the Impact of Network Impairments over Internet-Based Telemedicine Video Traffic

The Internet is designed to provide best effort service, which is not suitable for real-time applications. Therefore, carrying real-time applications over the Internet presents a number of challenges. While quality of service technologies can overcome some of these challenges, most medical facilities and patient homes do not utilize them since there is a high cost associated. Telemedicine and related technologies provide a promising opportunity to improve our healthcare reach to wider populations. The low cost and ubiquity of the Internet can help deliver healthcare to a wider population. However, the unreliable connection properties of packet-based systems hamper the quality of Internet-based telemedicine applications. This research is aimed to explore the delay, jitter, and drop cutoff points for Internet-based videoconferencing applications where video quality stays above the acceptable peak-signal-to-noise-ratio value (25dB). An experimental study is conducted on our testbed where behavior of the Internet is emulated on a Linux PC using NIST Net, a network emulation tool. Video file utilized during these experiments is an ophthalmology telemedicine session and it was obtained from the Regenstrief Institute for Health Care. Video quality measurements are computed using Video Quality Metric (VQM) software, which was developed by the Institute for Telecommunication Sciences (ITS). Our analysis and results indicate that jitter has a severe effect on the video quality whereas the effect of delay is almost invisible. Drop effects are similar to jitter with less impact on video quality. Results presented in this paper include the cutoff points for these variables as well.