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Perceptually transparent audio compression based on a variable bit rate AAC coder

The paper presents an implementation of a perceptually transparent variable bit rate (VBR) audio coder that complies with the MPEG-4 advanced audio coding (AAC) standard. The coder is based on the MPEG-4 reference software source code of CBR coder. With small modifications in the reference source code a coder guaranteeing perceptual transparency is achieved at compression ratios considerably better than that of the reference CBR coder. Comparison tests indicate that files generated by the perceptually transparent VBR coder applied to a standard set of test items are considerably smaller (in average 24%) than the smallest CBR files of the same quality.