PEVQ 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).
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.
PEVQ is a full reference, intrusive measurement algorithm for video quality.
Its basic structure is shown in the figure below.
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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.
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