Patent ID: 6915255
Filing Date: 2005-07-05
Classification: G10L

Abstract:
1. An audio signal encoding apparatus for dividing audio signal into a plurality of audio signal components each corresponding to a scale factor band to be encoded in accordance with a predetermined psychoacoustic model, comprising: inputting means for inputting said audio signal therein; frame length determining means for judging whether said audio signal inputted from said inputting means is transient or stationary, and determining a short-length frame for said audio signal when it is judged that said audio signal is transient and a long-length frame for said audio signal when it is judged that said audio signal is stationary; FFT analyzing means for performing the fast Fourier transform to said audio signal inputted from said inputting means to generate frequency information about said audio signal; coded mode information inputting means for inputting coded mode information; psychoacoustic model analyzing means for calculating Signal-to-Mask ratio information for said audio signal on the basis of said frequency information about said audio signal generated by said FFT analyzing means, in accordance with said predetermined psychoacoustic model; maximum scale factor band table storage means for storing initial maximum scale factor band information and Signal-to-Mask ratio threshold value information; initial maximum scale factor band calculation means for calculating an initial maximum scale factor band for said audio signal on the basis of the result made by said frame length determining means and said coded mode information inputted from said coded mode information inputting means with reference to said initial maximum scale factor band information and said Signal-to-Mask ratio threshold value information stored in said maximum scale factor band table storage means; maximum scale factor band calculation means for calculating a maximum scale factor band for said audio signal on the basis of said initial maximum scale factor band calculated by said initial maximum scale factor band calculation means in accordance with said Signal-to-Mask ratio information calculated by said psychoacoustic model analyzing means; spectral processing means for dividing said audio signal inputted from said inputting means into a plurality of audio signal components each corresponding to a scale factor band, and performing spectral processing to said audio signal components up to an audio signal component corresponding to said maximum scale factor band calculated by said maximum scale factor band calculation means, on the basis of said Signal-to-Mask ratio information calculated by said psychoacoustic model analyzing means to generate audio signal data; and quantizing and encoding means for quantizing and encoding said audio signal data generated by said spectral processing means to generate a coded audio signal to be outputted therethrough, whereby said maximum scale factor band calculation means is operative to adaptively calculate said maximum scale factor band in response to said audio signal inputted therein.