PEVQ – the Standard for Perceptual Evaluation of Video Quality
OPTICOM’s Perceptual Evaluation of Video Quality (PEVQ®) provides MOS scores of the video quality of IPTV, streaming video, mobile TV and video telephony. PEVQ is a full-reference (FR) perceptual measurement algorithm, meaning that it compares each frame of a video signal under test, employing pixel-based analysis, against the corresponding original (reference) video content, for example an uncompressed studio master, or an HD video at the head-end.
PEVQ measures degradations and artefacts resulting from video coding as well as network transmission by analyzing the degraded video signal captured from a network. Perceptual Quality-of-Experience (QoE) testing is based on modelling the behavior of the human visual tract and calculating an overall quality MOS score [from 1=bad to 5=excellent], which can be validated by subjective testing. In addition, the PEVQ algorithm will quantify distortions in the video signal by reporting additional KPIs, including PSNR, distortion indicators and lip-sync delay (in combination with audio analysis).
The performance of PEVQ was independently assessed by third parties in the course of several standardization benchmarks by the Video Quality Experts Group (VQEG). PEVQ was a winner of the VQEG Multimedia project and became part of ITU-T Recommendation J.247 in 2008. PEVQ-HD was evaluated by the VQEG HD project in 2010. PEVQ-S, an advanced hybrid version of PEVQ for IP-based video streaming was nominated winner of the latest VQEG hybrid benchmark in 2014. It is therefore anticipated that PEVQ-S will become part of a new ITU-T Recommendation of SG12.
OPTICOM, the leading provider of signal based perceptual measurement technology for voice, audio and video, offers its easy to use real-time PEVQ measurement as part of the PEXQ software suite for Windows, and has licensed PEVQ to a range of OEM vendors, including leading T&M manufacturers, network equipment manufacturers, software manufacturers and operators worldwide. The solutions cover different use cases including codec evaluation, drive test tools for video telephony, and IPTV test and monitoring equipment.
PEVQ Measurement Principle
PEVQ is a Full-Reference, intrusive Measurement Algorithm for Video Quality.
click on image to enlarge
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 the only differences taken into account would be those perceived by a human viewer. Furthermore the activity of the motion in the reference signal provides another indicator representing temporal information.
- The temporal information indicator is important as it considers that the perception of details is much higher in frame series with low activity, 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 ‘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 and jitter) and signal related impairments such as blockiness, jerkiness, blur and distortions caused by coding processes.
PEVQ Measurement 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.
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.
Specifications PEVQ - Perceptual Evaluation of Video Quality
Perceptual Evaluation of Video Quality-PEVQ, with mapping to MOS scale (1 bad, ... 5 excellent quality)
Analysis of HD, SD, VGA, CIF and QCIF video formats
Averaged benchmark for a 10s video test sequence [Windows PC with Intel Xeon 2x CPU E5-2620 2.6 GHz, 32GB RAM]:
HD (1080p) ..... 170s
VGA ................... 86s
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
PEVQ Form Factors
Stand-alone software for Windows PC
- PEXQ Software Suite, video option w/PEVQ
- Order-Code PXQ-000-EVQ-S » PEXQ Software Suite, video option w/PEVQ
PEVQ-HD Analyzer hardware system
- Order-Code PVQ-101-000-D » (Desktop version) –discontinued-
- Order-Code PVQ-102-000-R » (Rack-mount version) –discontinued-
PEVQ OEM Library for Windows, Linux (OEM license models available for system integrators and T&M manufacturers.)
- Order-Code OEM-xx00-EVQ-W » OEM libray for Windows
- Order-Code OEM-xx00-EVQ-L » OEM libray for Linux