Krasner's Audio Coder Revisited
An audio compression encoder and decoder system based on Krasner’s work was implemented. An improved Quadrature Mirror Filter tree, which more closely approximates modern critical band measurements, splits the input signal into sub bands that are encoded using both adaptive quantisation and entropy coding. The uniform adaptive quantisation scheme developed by Jayant was implemented and enhanced through the addition of non-uniform quantisation steps and look ahead. The complete codecs are evaluated using the perceptual audio evaluation algorithm PEAQ and their performance compared to equivalent MPEG-1 Layer III files. Initial, limited, tests reveal that the proposed codecs can score Objective Difference Grades close to or even better than MPEG-1 Layer III files encoded at a similar bit rate.
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