edu.cmu.sphinx.frontend.endpoint
Class SpeechClassifier

java.lang.Object
  edu.cmu.sphinx.util.props.ConfigurableAdapter
      edu.cmu.sphinx.frontend.BaseDataProcessor
          edu.cmu.sphinx.frontend.endpoint.SpeechClassifier

All Implemented Interfaces:

DataProcessor, Configurable

public class SpeechClassifier
extends BaseDataProcessor

Implements a level tracking endpointer invented by Bent Schmidt Nielsen.

This endpointer is composed of three main steps.

1. classification of audio into speech and non-speech
2. inserting SPEECH_START and SPEECH_END signals around speech
3. removing non-speech regions

The first step, classification of audio into speech and non-speech, uses Bent Schmidt Nielsen's algorithm. Each time audio comes in, the average signal level and the background noise level are updated, using the signal level of the current audio. If the average signal level is greater than the background noise level by a certain threshold value (configurable), then the current audio is marked as speech. Otherwise, it is marked as non-speech.

The second and third step of this endpointer are documented in the classes SpeechMarker and NonSpeechDataFilter.

See Also:

SpeechMarker

Field Summary

static java.lang.String	PROP_ADJUSTMENT A property specifying the adjustment.
static java.lang.String	PROP_FRAME_LENGTH_MS A property specifying the endpointing frame length in milliseconds.
static java.lang.String	PROP_MIN_SIGNAL A property specifying the minimum signal level used to update the background signal level.
static java.lang.String	PROP_THRESHOLD A property specifying the threshold.

Constructor Summary

SpeechClassifier()

SpeechClassifier(int frameLengthMs, double adjustment, double threshold, double minSignal)

Method Summary

Data	getData() Returns the next Data object.
void	initialize() Initializes this LevelTracker endpointer and DataProcessor predecessor.
boolean	isSpeech()
static double	logRootMeanSquare(double[] samples) Returns the logarithm base 10 of the root mean square of the given samples.
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

getPredecessor, getTimer, setPredecessor

Methods inherited from class edu.cmu.sphinx.util.props.ConfigurableAdapter

getName, toString

Methods inherited from class java.lang.Object

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

Field Detail

PROP_FRAME_LENGTH_MS

@S4Integer(defaultValue=10)
public static final java.lang.String PROP_FRAME_LENGTH_MS

A property specifying the endpointing frame length in milliseconds.

See Also:

Constant Field Values

PROP_MIN_SIGNAL

@S4Double(defaultValue=0.0)
public static final java.lang.String PROP_MIN_SIGNAL

A property specifying the minimum signal level used to update the background signal level.

See Also:

Constant Field Values

PROP_THRESHOLD

@S4Double(defaultValue=10.0)
public static final java.lang.String PROP_THRESHOLD

A property specifying the threshold. If the current signal level is greater than the background level by this threshold, then the current signal is marked as speech. Therefore, a lower threshold will make the endpointer more sensitive, that is, mark more audio as speech. A higher threshold will make the endpointer less sensitive, that is, mark less audio as speech.

See Also:

Constant Field Values

PROP_ADJUSTMENT

@S4Double(defaultValue=0.0030)
public static final java.lang.String PROP_ADJUSTMENT

A property specifying the adjustment.

See Also:

Constant Field Values

Constructor Detail

SpeechClassifier

public SpeechClassifier(int frameLengthMs,
                        double adjustment,
                        double threshold,
                        double minSignal)

SpeechClassifier

public SpeechClassifier()

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 ConfigurableAdapter

Parameters:

ps - a property sheet holding the new data

Throws:

PropertyException - if there is a problem with the properties.

initialize

public void initialize()

Initializes this LevelTracker endpointer and DataProcessor predecessor.

Specified by:

initialize in interface DataProcessor

Overrides:

initialize in class BaseDataProcessor

logRootMeanSquare

public static double logRootMeanSquare(double[] samples)

Returns the logarithm base 10 of the root mean square of the given samples.

Parameters:

samples - the samples

Returns:

the calculated log root mean square in log 10

getData

public Data getData()
             throws DataProcessingException

Returns the next Data object.

Specified by:

getData in interface DataProcessor

Specified by:

getData in class BaseDataProcessor

Returns:

the next Data object, or null if none available

Throws:

DataProcessingException - if a data processing error occurs

isSpeech

public boolean isSpeech()