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Browsing by Author "Lee, Wen-chieh"

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    High frequency reconstruction by linear extrapolation
    (2008-05-08)
    Liu, Chi-min
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    Lee, Wen-chieh
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    Hsu, Han-Wen
    High frequency components of audio signals are reconstructed from the aspects of envelope and fine detail. The envelopes of the high frequency components are found through linear extrapolation of signals with frequencies lower than a cutoff frequency point. One method of reconstructing high frequency components is based on the linear extrapolation on the logarithm scale magnitudes of the transform coefficients of the audio signal in a frequency domain. The linear extrapolation is a linear approximation based on minimizing least squares of the logarithm scale magnitudes of the transform coefficients of the low frequency components. Another method is based on the linear extrapolation on the logarithm scale magnitudes of the envelope elements of the filterbank signals of the audio signal over a time segment. The linear extrapolation is a linear approximation based on minimizing least squares of the logarithm scale magnitudes of the envelope elements of the low frequency filterbank signals.
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    Method of detecting for activating a temporal noise shaping process in coding audio signals
    (2008-01-03)
    Liu, Chi-min
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    Lee, Wen-chieh
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    Chang, Tzu-wen
    A method of detecting for activating a temporal noise shaping process in coding audio signals comprises the steps of receiving continuous audio signals; computing a perceptual entropy value of each audio signal; comparing the perceptual entropy value with a threshold according to a discriminative condition; and activating temporal noise shaping process when a corresponding result is set true.
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    Perceptual coding of audio signals by spectrum uncertainty
    (2008-01-03)
    Liu, Chi-min
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    Lee, Wen-chieh
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    Tin, Chiou
    A method for digital encoding of an audio stream in which the psychoacoustic modeling bases its computations upon an MDCT for the intensity and a spectral flatness measurement that replaces the phase data for the unpredictability measurement. This dramatically reduces computational overhead while also providing an improvement in objectively measured quality of the encoder output. This also allows for determination of tonal attacks to compute masking effects.