Perceptual Evaluation of
Video Quality
PEVQ provides mean opinion score (MOS) estimates of the video quality degradation occurring through a network, e.g. in video telephony networks. PEVQ can be ideally applied to testvideo streaming, video conferencing and IPTV applications. The degraded video signal output from a network is analyzed by comparison to the undistorted reference video signal on a perceptual basis. PEVQ is based on the approach to model the human visual system with which anomaly perceived in the video signal can be detected and quantified by a multitude of keyperformance indicators (KPIs).

After successful benchmarks by the Video Quality Experts Group (VQEG), PEVQ has become part of new ITU-T Recommendation J.247 (2008).
OPTICOM, the leading provider of signal based perceptual measurement technology for voice, audio and video, offers its new easy to use
PEVQ V 2.0 measurement as an OEM solution. PEVQ evaluates the quality of CIF, QCIF, VGA and Rec. 601 video formats based on perceptual measurement, reliably, objectively and fast.

PEVQ is based on the earlier PVQM technologydeveloped by KPN Research and new develop-ments of OPTICOM.

> Principle PEVQ is a full reference, intrusive measurement algorithm for video quality. Its basic structure is shown in the figure below.
click to [ enlarge picture ]

> Key Features
Accurate, reliable and fast objective analysis of perceived video quality

Full reference based end-to-end quality analysis

Outputs MOS score that correlates well with subjective MOS
Additional KPIs for detailed analysis
Measurement of multimedia (QCIF, CIF, VGA), SD and HD video quality
Applications: IPTV, streaming video, 3G, video telephony
Performance benchmarked by the Video Quality Experts Group (VQEG) and approved as new ITU-T Rec. J.247 (2008)
The algorithm can be divided up into four separate blocks. The first block – pre-processing stage – is responsible for the spatial and temporal alignment of the reference and the impaired signal. This process ensures that only corresponding frames are compared to each other.

The second block calculates the perceptual difference of the aligned signals. Perceptual means that only those differences are taken into account which are actually perceived by a human viewer. Furthermore the activity of the motion in the reference signal provides another indicator representing the temporal information.

This indicator is important as it takes into account that in frame series with low activity the perception of details is much higher than in frame series with quick motion.
The third block in the figure classifies the previously calculated indicators and detects certain types of distortions.

Finally, in the fourth block all the appropriate indicators according to the detected distortions are aggregated, forming the final result - the mean opinion score (MOS). The MOS value describes the video quality on a range from 1 for very bad quality, to 5 for excellent quality.

Besides the final quality score additional indicators are provided at the output of the algorithm for further cause analysis.

This approach to video quality estimation includes the effects of both packet level impairments (loss, jitter) and signal related impairments such as blockiness, jerkiness, blur and distortions caused by coding processes.

Future releases will be further optimized in computational performance and prediction accuracy to provide a complete picture of a quality estimate. OPTICOM’s roadmap for PEVQ targets at candidating in the competition of the Video Quality Experts Group (VQEG) for the best video quality measurement model.

> Specifications PEVQ - Perceptual Evaluation of Video Quality
Functionality Perceptual Evaluation of Video Quality-PEVQ, with mapping to MOS scale (1 bad, ... 5 excellent quality)
  Analysis of multimedia, SD and HD video formats
Input data Raw YUV, AVI Files with RGB24, YUV444, YUV422 or YUV420 data, any frame rate from 2,5 up to 60 fps

Video test sequences of 6 to 20 seconds duration

Complexity PEVQ is widely optimized and is capable of processing QCIF streams faster than realtime on a 3GHz Pentium 4 machine.
Platforms Windows
> Output
The PEVQ MOS value lies within a range from 1 (bad) to 5 (excellent). The PEVQ MOS is based on a multitude of perceptually motivated parameters and is calculated according to ITU-T Rec. J.247.
Distortion indicators
For a more detailed analysis the perceptual level of distortion in the luminance, chrominance and temporal domain are provided.
The delay of each frame of the test signal related to the reference signal.
The brightness of the reference and degraded signal.
The contrast of the distorted and the reference sequence.
To allow for a coarse analysis of distortions in different domains the PSNR is provided for the Y, Cb and Cr components separately.
describes the smoothness of a video playback which is often impaired by down-sampling, coding processes and perturbed transmissions.
is a distortion characterized by reduced sharpness of contour edges and spatial detail.
is often the result of a low bit rate coding that uses a block matching algorithm for the motion estimation and a coarse quantization for the image blocks.
Frame Skips and Freezes
are temporal artefacts occurring in video transmissions caused by e.g. overloaded networks.
Effective Frame Rate
Down-sampling of a video signal on a frame by frame basis often results in loss of information which often leads to the degradation of the video signal. The effective frame rate is an indicator quantifying the severeness of such a process.
Temporal and Spacial Activity
Temporal and spacial activity indicators quantify the amount of activity /movement in the video content. These indicators are derived from ITU-T recommendation P.910.
> Download more detailed information

Download PEVQ – Perceptual Evaluation of Video Quality
[as PDF / 224 kb]


Download New PEVQ Analyzer Data Sheet
[as PDF / 3 Mb]


Download OPTICOM Newsletter Spring 2008
[as PDF / 1,5 Mb]

-> Download "PEVQ™ Advanced Perceptual Evaluation of Video Quality"
[as PDF / 360 kb]
> www.PEVQ.org OPTICOM's new web portal comprises an up-to-date listing on commercially available video quality testing tools which can analyze the picture quality by providing a MOS score, just as subscribers would perceive the quality of a service.

A Market Overview on PEVQ embedding products reflects the application space for test tools in the life cycle of NGN's, while extending from pre-deployment feature testing for the lab, over load testing and test tools for installation and network optimization to IPTV test and monitoring equipment.

For the online version of the PEVQ Market Overview please go directly to