Abstract: When determining a quantization for digital audio signals having a spectral and temporal structure wherein the audio signals are buffered in frames and decomposed into spectral components, the method is: obtaining a variance and/or a representative of the components of the the frame within a defined frequency interval; computing a necessary bandwidth using psychoacoustic criteria; determining an initial quantization for each frequency interval using an approximate mathematical model; and iteratively increasing the quantization of each of the frequency intervals through a psychoacoustically weighted inverse relationship with the the variance of each of the frequency intervals.

Abstract: A method for enhancing a block companding uniform midtread quantizer in the ATRAC (Adaptive Transform Acoustic Coding) for the quantization of digital audio signals, wherein the audio signals are represented by a plurality of frames of quantized spectral components. The method includes modifying all spectral sample values in a defined frequency interval by a constant factor, calculating a scale factor for the frequency interval from a maximum spectral sample value, and quantizing all the spectral samples in the modified frequency interval with a modified quantizer.

Abstract: A method for determining the block size of a transform coder in which the digital audio signals having spectral and temporal structure are decomposed into plural spectral frames. The method involves defining the audio signal into time intervals according to the temporal masking properties of a human auditory system; obtaining a peak value in each of these time intervals; calculating differences among the peak values; and selecting a block size based on a comparison of the differences against a predefined value.

Abstract: A stereo audio encoding method for encoding left and right original signals to a left and right reproduced signals for suppressing a loss of quality in the reproduced audio signal. The correlation between the right and left channel signals is determined, and the phase of each signal is compared. If the two signals have the same phase, a modified scale factor is calculated based on a power equalization method, but if the two signals are in opposite phase, another modified scale factor is calculated based on an error minimization method. The modified scale factors are used for calculating the reproduced signals.