Andries Pieter Hekstra

Perceptual evaluation of speech quality (PESQ)-a new method for speech quality assessment of telephone networks and codecs

Previous objective speech quality assessment models, such as bark spectral distortion (BSD), the perceptual speech quality measure (PSQM), and measuring normalizing blocks (MNB), have been found to be suitable for assessing only a limited range of distortions. A new model has therefore been developed for use across a wider range of network conditions, including analogue connections, codecs, packet loss and variable delay. Known as perceptual evaluation of speech quality (PESQ), it is the result of integration of the perceptual analysis measurement system (PAMS) and PSQM99, an enhanced version of PSQM. PESQ is expected to become a new ITU-T recommendation P.862, replacing P.861 which specified PSQM and MNB.

Video Quality Experts Group: Current Results and Future Directions

The Video Quality Experts Group (VQEG) was formed in October 1997 to address video quality issues. The group is composed of experts from various backgrounds and affiliations, including participants from several internationally recognized organizations working int he field of video quality assessment. The first task undertaken by VQEG was to provide a validation of objective video quality measurement methods leading to recommendations in both the telecommunications and radiocommunication sectors of the International Telecommunications Union. To this end, VQEG designed and executed a test program to compare subjective video quality evaluations to the predictions of a number of proposed objective measurement methods for video quality in the bit rate range of 768 kb/s to 50 Mb/s. The results of this test show that there is no objective measurement system that is currently able to replace subjective testing. Depending on the metric used for evaluation, the performance of eight or nine models was found to be statistically equivalent, leading to the conclusion that no single model outperforms the others in all cases. The greatest achievement of this first validation effort is the unique data set assembled to help future development of objective models.

PVQM – A perceptual video quality measure

Abstract Modern video coding systems such as ISO-MPEG1,2,4 exploit properties of the human visual system, to reduce the bit rate at which a video sequence is coded, given a certain required video quality. As a result, to the degree in which such exploitation is successful, accurate prediction of the quality of the output video of such systems, should also take the human visual system into account. In this paper, we propose a perceptual video quality system, that uses a linear combination of three indicators. The indicators are, the “edginess” of the luminance, the normalized color error and the temporal decorrelation. In the benchmark by the Video Quality Expert Group (VQEG), a combined ITU-T and ITU-R expert group, the model showed the highest variance weighted regression overall correlation of all models.