engleski

Evaluation of perceptually encoded digital audio through transparency reduction

There are a number of well known and established methods used for distortion measurements in audio systems, but they cannot be used for detecting errors that appear in digital audio systems based on perceptual coding and decoding. For that reason, a test stimulus has to be used that has the time-varying properties similar to real-life signals, such as speech and music. Moreover, the procedure of quality evaluation has to include an estimate of the temporal behaviour of human hearing. This paper describes a new complex test signal developed for the purpose of evaluating digital audio systems based on perceptual coding with the cumulative amplitude distribution following the Gaussian distribution. In order to try out this new test signal, it was applied in a number of standard audio encoders. A reduction in transparency was defined as a measure of distortion, being the ratio of error excitation and stimulus excitation. The values of transparency reduction are compared to subjective ratings of audio quality.

perceptual coding; digital audio; transparency reduction

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