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java.lang.Objectedu.cmu.sphinx.frontend.frequencywarp.PLPFilter
Defines a filter used by the PLPFrequencyFilterBank
class. The
filter is defined by a function in the Constructor
. A set of equally spaced frequencies in a linear scale
is passed to the constructor, which returns the weights for each of
the frequency bins, such that the filter has the shape defined by
this piecewise function in the bark scale.
PLPFrequencyFilterBank
Field Summary | |
double |
centerFreqInBark
The center frequency of the filter in Bark. |
double |
centerFreqInHz
The center frequency of the filter in Hertz. |
Constructor Summary | |
PLPFilter(double[] DFTFrequenciesInHz,
double centerFreqInHz)
Constructs a PLP filter around a given center frequency. |
Method Summary | |
double |
filterOutput(double[] spectrum)
Compute the PLP spectrum at the center frequency of this filter for a given power spectrum. |
Methods inherited from class java.lang.Object |
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
public double centerFreqInHz
public double centerFreqInBark
Constructor Detail |
public PLPFilter(double[] DFTFrequenciesInHz, double centerFreqInHz) throws java.lang.IllegalArgumentException
Filter(f) = 0 if f < -2.5The current implementation assumes that the calling routine passes in an array of frequencies, one for each of the DFT points in the spectrum of the frame of speech to be filtered. This is used in conjunction with a specified center frequency to determine the filter.
= 10^(-(f+0.5)) if -2.5 <= f <= -0.5
= 1 if -0.5 <= f <= 0.5
= 10^(2.5(f-0.5)) if 0.5 <= f <= 1.3
= 0 if f > 1.3
DFTFrequenciesInHz
- is a double array containing the frequencies
in Hertz corresponding to each of the DFT points in the spectrum
of the signal to be filtered.centerFreqInHz
- is the filter's center frequency
java.lang.IllegalArgumentException
Method Detail |
public double filterOutput(double[] spectrum) throws java.lang.IllegalArgumentException
spectrum
- the input power spectrum to be filtered
java.lang.IllegalArgumentException
- if the input spectrum is of a
different length than the array of filter coefficients
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