Quality Measurement of Perceptual Audio Codecs

Audio coding involves balancing data rate and system complexity limitations against needs for high-quality audio. While audio quality is a fundamental concept in audio coding, it remains very difficult to describe it in objective terms. Traditional quality measurements such as the signal to noise ratio or the total block distortion provide simple, objective measures of audio quality but they ignore psychoacoustic effects that can lead to large differences in perceived quality. In contrast, perceptual objective measurement schemes, which rely upon specific models of hearing, are subject to the criticism that the predicted results do not correlate well with the perceived audio quality. While neither simple objective measures nor perceptual measures are considered fully satisfactory, audio coding has traditionally relied on formal listening tests to assess a system’s audio quality when a highly accurate assessment is needed. After all, human listeners are the ultimate judges of quality in any application.