Patent ID: 8504181

Claim:
A method for processing an audio signal represented by the Modified Discrete Cosine Transform (MDCT) of a time-sampled real signal, comprising measuring in the MDCT domain the perceived loudness of the MDCT-transformed audio signal, wherein said measuring includes computing an estimate of the power spectrum of the MDCT-transformed audio signal, wherein said computing an estimate employs weighting to compensate for the MDCT's representation of only one of the quadrature components of the transformed audio signal and smoothing time constants commensurate with the integration time of human loudness perception or slower, and modifying in the MDCT domain, at least in part in response to said measuring, the perceived loudness of the transformed audio signal, wherein said modifying includes gain modifying frequency bands of the MDCT-transformed audio signal, the rate of change of the gain across frequency being constrained by a smoothing function that limits the degree of aliasing distortion.