Glossary

PSNR, an abbreviation of Peak Signal-to-Noise Ratio, a term used to describe objectively the quality of data, which is the result of decompressing encoded data. For example, the quality of a certain image in a video bit stream.

PSNR is the ratio between the maximum possible power of a signal and the power of corrupting noise that affects the fidelity of its representation. Because many signals have a very wide dynamic range, PSNR is usually expressed in terms of a logarithmic decibel scale.

A higher PSNR value indicates that the reconstruction is of higher quality. Typical values for the PSNR in a lossy image and video compression are between 30 and 50dB, where higher is better. Acceptable values for wireless transmission quality loss are considered to be about 20dB to 25dB.

PSNR is most commonly used as a measure of quality of reconstruction of lossy compression codecs. The signal in this case is the original data, and the noise is the error introduced by compression. It is also useful to compare various codecs, as it estimates the perceived quality of the result. Although PSNR is regarded as a quality measure, in some cases a reconstruction may appear to be closer to the original than another, even though it has a lower PSNR.