edu.cmu.sphinx.frontend.util

Class Microphone

java.lang.Object

edu.cmu.sphinx.util.props.ConfigurableAdapter

edu.cmu.sphinx.frontend.BaseDataProcessor

edu.cmu.sphinx.frontend.util.Microphone

All Implemented Interfaces:

DataProcessor, Configurable

public class Microphone
extends BaseDataProcessor

A Microphone captures audio data from the system's underlying audio input systems. Converts these audio data into Data objects. When the method startRecording() is called, a new thread will be created and used to capture audio, and will stop when stopRecording() is called. Calling getData() returns the captured audio data as Data objects.

This Microphone will attempt to obtain an audio device with the format specified in the configuration. If such a device with that format cannot be obtained, it will try to obtain a device with an audio format that has a higher sample rate than the configured sample rate, while the other parameters of the format (i.e., sample size, endianness, sign, and channel) remain the same. If, again, no such device can be obtained, it flags an error, and a call startRecording returns false.

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	PROP_BIG_ENDIAN The property specify the endianness of the data.
static java.lang.String	PROP_BITS_PER_SAMPLE The property for the number of bits per value.
static java.lang.String	PROP_BUFFER_SIZE The property that specifies the size of the buffer used to store audio samples recorded from the microphone.
static java.lang.String	PROP_CHANNELS The property specifying the number of channels.
static java.lang.String	PROP_CLOSE_BETWEEN_UTTERANCES The property that specifies whether or not the microphone will release the audio between utterances.
static java.lang.String	PROP_KEEP_LAST_AUDIO The property that specifies whether to keep the audio data of an utterance around until the next utterance is recorded.
static java.lang.String	PROP_MSEC_PER_READ The property that specifies the number of milliseconds of audio data to read each time from the underlying Java Sound audio device.
static java.lang.String	PROP_SAMPLE_RATE The property for the sample rate of the data.
static java.lang.String	PROP_SELECT_CHANNEL The property that specifies the channel to use if the audio is stereo
static java.lang.String	PROP_SELECT_MIXER The property that specifies the mixer to use.
static java.lang.String	PROP_SIGNED The property specify whether the data is signed.
static java.lang.String	PROP_STEREO_TO_MONO The property that specifies how to convert stereo audio to mono.

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

logger

Constructor Summary

Constructors

Constructor and Description
Microphone()
Microphone(int sampleRate, int bitsPerSample, int channels, boolean bigEndian, boolean signed, boolean closeBetweenUtterances, int msecPerRead, boolean keepLastAudio, java.lang.String stereoToMono, int selectedChannel, java.lang.String selectedMixerIndex, int audioBufferSize)

Method Summary

Modifier and Type	Method and Description
void	clear() Clears all cached audio data.
javax.sound.sampled.AudioFormat	getAudioFormat() Returns the format of the audio recorded by this Microphone.
Data	getData() Reads and returns the next Data object from this Microphone, return null if there is no more audio data.
Utterance	getUtterance() Returns the current Utterance.
boolean	hasMoreData() Returns true if there is more data in the Microphone.
void	initialize() Constructs a Microphone with the given InputStream.
boolean	isRecording() Returns true if this Microphone is recording.
void	newProperties(PropertySheet ps) This method is called when this configurable component needs to be reconfigured.
boolean	startRecording() Starts recording audio.
void	stopRecording() Stops recording audio.

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

getPredecessor, setPredecessor

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

getName, initLogger, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

PROP_SAMPLE_RATE

@S4Integer(defaultValue=16000)
public static final java.lang.String PROP_SAMPLE_RATE

The property for the sample rate of the data.

See Also:

Constant Field Values

PROP_CLOSE_BETWEEN_UTTERANCES

@S4Boolean(defaultValue=true)
public static final java.lang.String PROP_CLOSE_BETWEEN_UTTERANCES

The property that specifies whether or not the microphone will release the audio between utterances. On certain systems (Linux for one), closing and reopening the audio does not work too well. The default is false for Linux systems, true for others.

See Also:

Constant Field Values

PROP_MSEC_PER_READ

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

The property that specifies the number of milliseconds of audio data to read each time from the underlying Java Sound audio device.

See Also:

Constant Field Values

PROP_BITS_PER_SAMPLE

@S4Integer(defaultValue=16)
public static final java.lang.String PROP_BITS_PER_SAMPLE

The property for the number of bits per value.

See Also:

Constant Field Values

PROP_CHANNELS

@S4Integer(defaultValue=1)
public static final java.lang.String PROP_CHANNELS

The property specifying the number of channels.

See Also:

Constant Field Values

PROP_BIG_ENDIAN

@S4Boolean(defaultValue=true)
public static final java.lang.String PROP_BIG_ENDIAN

The property specify the endianness of the data.

See Also:

Constant Field Values

PROP_SIGNED

@S4Boolean(defaultValue=true)
public static final java.lang.String PROP_SIGNED

The property specify whether the data is signed.

See Also:

Constant Field Values

PROP_KEEP_LAST_AUDIO

@S4Boolean(defaultValue=false)
public static final java.lang.String PROP_KEEP_LAST_AUDIO

The property that specifies whether to keep the audio data of an utterance around until the next utterance is recorded.

See Also:

Constant Field Values

PROP_STEREO_TO_MONO

@S4String(defaultValue="average",
          range={"average","selectChannel"})
public static final java.lang.String PROP_STEREO_TO_MONO

The property that specifies how to convert stereo audio to mono. Currently, the possible values are "average", which averages the samples from at each channel, or "selectChannel", which chooses audio only from that channel. If you choose "selectChannel", you should also specify which channel to use with the "selectChannel" property.

See Also:

Constant Field Values

PROP_SELECT_CHANNEL

@S4Integer(defaultValue=0)
public static final java.lang.String PROP_SELECT_CHANNEL

The property that specifies the channel to use if the audio is stereo

See Also:

Constant Field Values

PROP_SELECT_MIXER

@S4String(defaultValue="default")
public static final java.lang.String PROP_SELECT_MIXER

The property that specifies the mixer to use. The value can be "default," (which means let the AudioSystem decide), "last," (which means select the last Mixer supported by the AudioSystem), which appears to be what is often used for USB headsets, or an integer value which represents the index of the Mixer.Info that is returned by AudioSystem.getMixerInfo(). To get the list of Mixer.Info objects, run the AudioTool application with a command line argument of "-dumpMixers".

See Also:

AudioTool, Constant Field Values

PROP_BUFFER_SIZE

@S4Integer(defaultValue=6400)
public static final java.lang.String PROP_BUFFER_SIZE

The property that specifies the size of the buffer used to store audio samples recorded from the microphone. Default value correspond to 200ms. Smaller value decrease microphone latency with danger of dropping out the frames if decoding thread will be slow enough to process the result.

See Also:

Constant Field Values

Constructor Detail

Microphone

public Microphone(int sampleRate,
                  int bitsPerSample,
                  int channels,
                  boolean bigEndian,
                  boolean signed,
                  boolean closeBetweenUtterances,
                  int msecPerRead,
                  boolean keepLastAudio,
                  java.lang.String stereoToMono,
                  int selectedChannel,
                  java.lang.String selectedMixerIndex,
                  int audioBufferSize)

Parameters:

sampleRate - sample rate of the data

bitsPerSample - number of bits per value.

channels - number of channels.

bigEndian - the endianness of the data

signed - whether the data is signed.

closeBetweenUtterances - whether or not the microphone will release the audio between utterances. On certain systems (Linux for one), closing and reopening the audio does not work too well. The default is false for Linux systems, true for others

msecPerRead - the number of milliseconds of audio data to read each time from the underlying Java Sound audio device.

keepLastAudio - whether to keep the audio data of an utterance around until the next utterance is recorded.

stereoToMono - how to convert stereo audio to mono. Currently, the possible values are "average", which averages the samples from at each channel, or "selectChannel", which chooses audio only from that channel. If you choose "selectChannel", you should also specify which channel to use with the "selectChannel" property.

selectedChannel - the channel to use if the audio is stereo

selectedMixerIndex - the mixer to use. The value can be "default," (which means let the AudioSystem decide), "last," (which means select the last Mixer supported by the AudioSystem), which appears to be what is often used for USB headsets, or an integer value which represents the index of the Mixer.Info that is returned by AudioSystem.getMixerInfo(). To get the list of Mixer.Info objects, run the AudioTool application with a command line argument of "-dumpMixers".

audioBufferSize - buffer size

Microphone

public Microphone()

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()

Constructs a Microphone with the given InputStream.

Specified by:

initialize in interface DataProcessor

Overrides:

initialize in class BaseDataProcessor

getAudioFormat

public javax.sound.sampled.AudioFormat getAudioFormat()

Returns the format of the audio recorded by this Microphone. Note that this might be different from the configured format.

Returns:

the current AudioFormat

getUtterance

public Utterance getUtterance()

Returns the current Utterance.

Returns:

the current Utterance

isRecording

public boolean isRecording()

Returns true if this Microphone is recording.

Returns:

true if this Microphone is recording, false otherwise

startRecording

public boolean startRecording()

Starts recording audio. This method will return only when a START event is received, meaning that this Microphone has started capturing audio.

Returns:

true if the recording started successfully; false otherwise

stopRecording

public void stopRecording()

Stops recording audio. This method does not return until recording has been stopped and all data has been read from the audio line.

clear

public void clear()

Clears all cached audio data.

getData

public Data getData()
             throws DataProcessingException

Reads and returns the next Data object from this Microphone, return null if there is no more audio data. All audio data captured in-between startRecording() and stopRecording() is cached in an Utterance object. Calling this method basically returns the next chunk of audio data cached in this Utterance.

Specified by:

getData in interface DataProcessor

Specified by:

getData in class BaseDataProcessor

Returns:

the next Data or null if none is available

Throws:

DataProcessingException - if there is a data processing error

hasMoreData

public boolean hasMoreData()

Returns true if there is more data in the Microphone. This happens either if the a DataEndSignal data was not taken from the buffer, or if the buffer in the Microphone is not yet empty.

Returns:

true if there is more data in the Microphone