edu.cmu.sphinx.frontend.transform
Class DiscreteCosineTransform

java.lang.Object
  edu.cmu.sphinx.frontend.BaseDataProcessor
      edu.cmu.sphinx.frontend.transform.DiscreteCosineTransform

All Implemented Interfaces:

DataProcessor, Configurable

public class DiscreteCosineTransform
extends BaseDataProcessor

Applies a logarithm and then a Discrete Cosine Transform (DCT) to the input data. The input data is normally the mel spectrum. It has been proven that, for a sequence of real numbers, the discrete cosine transform is equivalent to the discrete Fourier transform. Therefore, this class corresponds to the last stage of converting a signal to cepstra, defined as the inverse Fourier transform of the logarithm of the Fourier transform of a signal. The property PROP_CEPSTRUM_LENGTHrefers to the dimensionality of the coefficients that are actually returned, defaulting to PROP_CEPSTRUM_LENGTH_DEFAULT. When the input is mel-spectrum, the vector returned is the MFCC (Mel-Frequency Cepstral Coefficient) vector, where the 0-th element is the energy value.

Field Summary

static java.lang.String	PROP_CEPSTRUM_LENGTH The name of the sphinx property for the size of the ceptrum
static int	PROP_CEPSTRUM_LENGTH_DEFAULT The default value for PROP_CEPSTRUM_LENGTH
static java.lang.String	PROP_NUMBER_FILTERS The name of the Sphinx Property for the number of filters in the filterbank.
static int	PROP_NUMBER_FILTERS_DEFAULT The default value for PROP_NUMBER_FILTERS.

Constructor Summary

DiscreteCosineTransform()

Method Summary

Data	getData() Returns the next DoubleData object, which is the mel cepstrum of the input frame.
void	initialize() Initializes this DataProcessor.
void	newProperties(PropertySheet ps) This method is called when this configurable component needs to be reconfigured.

Methods inherited from class edu.cmu.sphinx.frontend.BaseDataProcessor

getName, getPredecessor, getTimer, setPredecessor, toString

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

PROP_NUMBER_FILTERS

@S4Integer(defaultValue=40)
public static final java.lang.String PROP_NUMBER_FILTERS

The name of the Sphinx Property for the number of filters in the filterbank.

See Also:

Constant Field Values

PROP_NUMBER_FILTERS_DEFAULT

public static final int PROP_NUMBER_FILTERS_DEFAULT

The default value for PROP_NUMBER_FILTERS.

See Also:

Constant Field Values

PROP_CEPSTRUM_LENGTH

@S4Integer(defaultValue=13)
public static final java.lang.String PROP_CEPSTRUM_LENGTH

The name of the sphinx property for the size of the ceptrum

See Also:

Constant Field Values

PROP_CEPSTRUM_LENGTH_DEFAULT

public static final int PROP_CEPSTRUM_LENGTH_DEFAULT

The default value for PROP_CEPSTRUM_LENGTH

See Also:

Constant Field Values

Constructor Detail

DiscreteCosineTransform

public DiscreteCosineTransform()

Method Detail

newProperties

public void newProperties(PropertySheet ps)
                   throws PropertyException

Description copied from interface: Configurable

This method is called when this configurable component needs to be reconfigured.

Specified by:

newProperties in interface Configurable

Overrides:

newProperties in class BaseDataProcessor

Parameters:

ps - a property sheet holding the new data

Throws:

PropertyException - if there is a problem with the properties.

initialize

public void initialize()

Description copied from class: BaseDataProcessor

Initializes this DataProcessor. This is typically called after the DataProcessor has been configured.

Specified by:

initialize in interface DataProcessor

Overrides:

initialize in class BaseDataProcessor

getData

public Data getData()
             throws DataProcessingException

Returns the next DoubleData object, which is the mel cepstrum of the input frame. Signals are returned unmodified.

Specified by:

getData in interface DataProcessor

Specified by:

getData in class BaseDataProcessor

Returns:

the next available DoubleData melcepstrum, or Signal object, or null if no Data is available

Throws:

DataProcessingException - if a data processing error occurred