The DataLine.java Java example source code
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package javax.sound.sampled;
import java.util.Arrays;
/**
* <code>DataLine adds media-related functionality to its
* superinterface, <code>{@link Line}. This functionality includes
* transport-control methods that start, stop, drain, and flush
* the audio data that passes through the line. A data line can also
* report the current position, volume, and audio format of the media.
* Data lines are used for output of audio by means of the
* subinterfaces <code>{@link SourceDataLine} or
* <code>{@link Clip}, which allow an application program to write data. Similarly,
* audio input is handled by the subinterface <code>{@link TargetDataLine},
* which allows data to be read.
* <p>
* A data line has an internal buffer in which
* the incoming or outgoing audio data is queued. The
* <code>{@link #drain()} method blocks until this internal buffer
* becomes empty, usually because all queued data has been processed. The
* <code>{@link #flush()} method discards any available queued data
* from the internal buffer.
* <p>
* A data line produces <code>{@link LineEvent.Type#START START} and
* <code>{@link LineEvent.Type#STOP STOP} events whenever
* it begins or ceases active presentation or capture of data. These events
* can be generated in response to specific requests, or as a result of
* less direct state changes. For example, if <code>{@link #start()} is called
* on an inactive data line, and data is available for capture or playback, a
* <code>START event will be generated shortly, when data playback
* or capture actually begins. Or, if the flow of data to an active data
* line is constricted so that a gap occurs in the presentation of data,
* a <code>STOP event is generated.
* <p>
* Mixers often support synchronized control of multiple data lines.
* Synchronization can be established through the Mixer interface's
* <code>{@link Mixer#synchronize synchronize} method.
* See the description of the <code>{@link Mixer Mixer} interface
* for a more complete description.
*
* @author Kara Kytle
* @see LineEvent
* @since 1.3
*/
public interface DataLine extends Line {
/**
* Drains queued data from the line by continuing data I/O until the
* data line's internal buffer has been emptied.
* This method blocks until the draining is complete. Because this is a
* blocking method, it should be used with care. If <code>drain()
* is invoked on a stopped line that has data in its queue, the method will
* block until the line is running and the data queue becomes empty. If
* <code>drain() is invoked by one thread, and another continues to
* fill the data queue, the operation will not complete.
* This method always returns when the data line is closed.
*
* @see #flush()
*/
public void drain();
/**
* Flushes queued data from the line. The flushed data is discarded.
* In some cases, not all queued data can be discarded. For example, a
* mixer can flush data from the buffer for a specific input line, but any
* unplayed data already in the output buffer (the result of the mix) will
* still be played. You can invoke this method after pausing a line (the
* normal case) if you want to skip the "stale" data when you restart
* playback or capture. (It is legal to flush a line that is not stopped,
* but doing so on an active line is likely to cause a discontinuity in the
* data, resulting in a perceptible click.)
*
* @see #stop()
* @see #drain()
*/
public void flush();
/**
* Allows a line to engage in data I/O. If invoked on a line
* that is already running, this method does nothing. Unless the data in
* the buffer has been flushed, the line resumes I/O starting
* with the first frame that was unprocessed at the time the line was
* stopped. When audio capture or playback starts, a
* <code>{@link LineEvent.Type#START START} event is generated.
*
* @see #stop()
* @see #isRunning()
* @see LineEvent
*/
public void start();
/**
* Stops the line. A stopped line should cease I/O activity.
* If the line is open and running, however, it should retain the resources required
* to resume activity. A stopped line should retain any audio data in its buffer
* instead of discarding it, so that upon resumption the I/O can continue where it left off,
* if possible. (This doesn't guarantee that there will never be discontinuities beyond the
* current buffer, of course; if the stopped condition continues
* for too long, input or output samples might be dropped.) If desired, the retained data can be
* discarded by invoking the <code>flush method.
* When audio capture or playback stops, a <code>{@link LineEvent.Type#STOP STOP} event is generated.
*
* @see #start()
* @see #isRunning()
* @see #flush()
* @see LineEvent
*/
public void stop();
/**
* Indicates whether the line is running. The default is <code>false.
* An open line begins running when the first data is presented in response to an
* invocation of the <code>start method, and continues
* until presentation ceases in response to a call to <code>stop or
* because playback completes.
* @return <code>true if the line is running, otherwise false
* @see #start()
* @see #stop()
*/
public boolean isRunning();
/**
* Indicates whether the line is engaging in active I/O (such as playback
* or capture). When an inactive line becomes active, it sends a
* <code>{@link LineEvent.Type#START START} event to its listeners. Similarly, when
* an active line becomes inactive, it sends a
* <code>{@link LineEvent.Type#STOP STOP} event.
* @return <code>true if the line is actively capturing or rendering
* sound, otherwise <code>false
* @see #isOpen
* @see #addLineListener
* @see #removeLineListener
* @see LineEvent
* @see LineListener
*/
public boolean isActive();
/**
* Obtains the current format (encoding, sample rate, number of channels,
* etc.) of the data line's audio data.
*
* <p>If the line is not open and has never been opened, it returns
* the default format. The default format is an implementation
* specific audio format, or, if the <code>DataLine.Info
* object, which was used to retrieve this <code>DataLine,
* specifies at least one fully qualified audio format, the
* last one will be used as the default format. Opening the
* line with a specific audio format (e.g.
* {@link SourceDataLine#open(AudioFormat)}) will override the
* default format.
*
* @return current audio data format
* @see AudioFormat
*/
public AudioFormat getFormat();
/**
* Obtains the maximum number of bytes of data that will fit in the data line's
* internal buffer. For a source data line, this is the size of the buffer to
* which data can be written. For a target data line, it is the size of
* the buffer from which data can be read. Note that
* the units used are bytes, but will always correspond to an integral
* number of sample frames of audio data.
*
* @return the size of the buffer in bytes
*/
public int getBufferSize();
/**
* Obtains the number of bytes of data currently available to the
* application for processing in the data line's internal buffer. For a
* source data line, this is the amount of data that can be written to the
* buffer without blocking. For a target data line, this is the amount of data
* available to be read by the application. For a clip, this value is always
* 0 because the audio data is loaded into the buffer when the clip is opened,
* and persists without modification until the clip is closed.
* <p>
* Note that the units used are bytes, but will always
* correspond to an integral number of sample frames of audio data.
* <p>
* An application is guaranteed that a read or
* write operation of up to the number of bytes returned from
* <code>available() will not block; however, there is no guarantee
* that attempts to read or write more data will block.
*
* @return the amount of data available, in bytes
*/
public int available();
/**
* Obtains the current position in the audio data, in sample frames.
* The frame position measures the number of sample
* frames captured by, or rendered from, the line since it was opened.
* This return value will wrap around after 2^31 frames. It is recommended
* to use <code>getLongFramePosition instead.
*
* @return the number of frames already processed since the line was opened
* @see #getLongFramePosition()
*/
public int getFramePosition();
/**
* Obtains the current position in the audio data, in sample frames.
* The frame position measures the number of sample
* frames captured by, or rendered from, the line since it was opened.
*
* @return the number of frames already processed since the line was opened
* @since 1.5
*/
public long getLongFramePosition();
/**
* Obtains the current position in the audio data, in microseconds.
* The microsecond position measures the time corresponding to the number
* of sample frames captured by, or rendered from, the line since it was opened.
* The level of precision is not guaranteed. For example, an implementation
* might calculate the microsecond position from the current frame position
* and the audio sample frame rate. The precision in microseconds would
* then be limited to the number of microseconds per sample frame.
*
* @return the number of microseconds of data processed since the line was opened
*/
public long getMicrosecondPosition();
/**
* Obtains the current volume level for the line. This level is a measure
* of the signal's current amplitude, and should not be confused with the
* current setting of a gain control. The range is from 0.0 (silence) to
* 1.0 (maximum possible amplitude for the sound waveform). The units
* measure linear amplitude, not decibels.
*
* @return the current amplitude of the signal in this line, or
* <code>{@link AudioSystem#NOT_SPECIFIED}
*/
public float getLevel();
/**
* Besides the class information inherited from its superclass,
* <code>DataLine.Info provides additional information specific to data lines.
* This information includes:
* <ul>
* <li> the audio formats supported by the data line
* <li> the minimum and maximum sizes of its internal buffer
* </ul>
* Because a <code>Line.Info knows the class of the line its describes, a
* <code>DataLine.Info object can describe DataLine
* subinterfaces such as <code>{@link SourceDataLine},
* <code>{@link TargetDataLine}, and {@link Clip}.
* You can query a mixer for lines of any of these types, passing an appropriate
* instance of <code>DataLine.Info as the argument to a method such as
* <code>{@link Mixer#getLine Mixer.getLine(Line.Info)}.
*
* @see Line.Info
* @author Kara Kytle
* @since 1.3
*/
public static class Info extends Line.Info {
private final AudioFormat[] formats;
private final int minBufferSize;
private final int maxBufferSize;
/**
* Constructs a data line's info object from the specified information,
* which includes a set of supported audio formats and a range for the buffer size.
* This constructor is typically used by mixer implementations
* when returning information about a supported line.
*
* @param lineClass the class of the data line described by the info object
* @param formats set of formats supported
* @param minBufferSize minimum buffer size supported by the data line, in bytes
* @param maxBufferSize maximum buffer size supported by the data line, in bytes
*/
public Info(Class<?> lineClass, AudioFormat[] formats, int minBufferSize, int maxBufferSize) {
super(lineClass);
if (formats == null) {
this.formats = new AudioFormat[0];
} else {
this.formats = Arrays.copyOf(formats, formats.length);
}
this.minBufferSize = minBufferSize;
this.maxBufferSize = maxBufferSize;
}
/**
* Constructs a data line's info object from the specified information,
* which includes a single audio format and a desired buffer size.
* This constructor is typically used by an application to
* describe a desired line.
*
* @param lineClass the class of the data line described by the info object
* @param format desired format
* @param bufferSize desired buffer size in bytes
*/
public Info(Class<?> lineClass, AudioFormat format, int bufferSize) {
super(lineClass);
if (format == null) {
this.formats = new AudioFormat[0];
} else {
this.formats = new AudioFormat[]{format};
}
this.minBufferSize = bufferSize;
this.maxBufferSize = bufferSize;
}
/**
* Constructs a data line's info object from the specified information,
* which includes a single audio format.
* This constructor is typically used by an application to
* describe a desired line.
*
* @param lineClass the class of the data line described by the info object
* @param format desired format
*/
public Info(Class<?> lineClass, AudioFormat format) {
this(lineClass, format, AudioSystem.NOT_SPECIFIED);
}
/**
* Obtains a set of audio formats supported by the data line.
* Note that <code>isFormatSupported(AudioFormat) might return
* <code>true for certain additional formats that are missing from
* the set returned by <code>getFormats(). The reverse is not
* the case: <code>isFormatSupported(AudioFormat) is guaranteed to return
* <code>true for all formats returned by getFormats().
*
* Some fields in the AudioFormat instances can be set to
* {@link javax.sound.sampled.AudioSystem#NOT_SPECIFIED NOT_SPECIFIED}
* if that field does not apply to the format,
* or if the format supports a wide range of values for that field.
* For example, a multi-channel device supporting up to
* 64 channels, could set the channel field in the
* <code>AudioFormat instances returned by this
* method to <code>NOT_SPECIFIED.
*
* @return a set of supported audio formats.
* @see #isFormatSupported(AudioFormat)
*/
public AudioFormat[] getFormats() {
return Arrays.copyOf(formats, formats.length);
}
/**
* Indicates whether this data line supports a particular audio format.
* The default implementation of this method simply returns <code>true if
* the specified format matches any of the supported formats.
*
* @param format the audio format for which support is queried.
* @return <code>true if the format is supported, otherwise false
* @see #getFormats
* @see AudioFormat#matches
*/
public boolean isFormatSupported(AudioFormat format) {
for (int i = 0; i < formats.length; i++) {
if (format.matches(formats[i])) {
return true;
}
}
return false;
}
/**
* Obtains the minimum buffer size supported by the data line.
* @return minimum buffer size in bytes, or <code>AudioSystem.NOT_SPECIFIED
*/
public int getMinBufferSize() {
return minBufferSize;
}
/**
* Obtains the maximum buffer size supported by the data line.
* @return maximum buffer size in bytes, or <code>AudioSystem.NOT_SPECIFIED
*/
public int getMaxBufferSize() {
return maxBufferSize;
}
/**
* Determines whether the specified info object matches this one.
* To match, the superclass match requirements must be met. In
* addition, this object's minimum buffer size must be at least as
* large as that of the object specified, its maximum buffer size must
* be at most as large as that of the object specified, and all of its
* formats must match formats supported by the object specified.
* @return <code>true if this object matches the one specified,
* otherwise <code>false.
*/
public boolean matches(Line.Info info) {
if (! (super.matches(info)) ) {
return false;
}
Info dataLineInfo = (Info)info;
// treat anything < 0 as NOT_SPECIFIED
// demo code in old Java Sound Demo used a wrong buffer calculation
// that would lead to arbitrary negative values
if ((getMaxBufferSize() >= 0) && (dataLineInfo.getMaxBufferSize() >= 0)) {
if (getMaxBufferSize() > dataLineInfo.getMaxBufferSize()) {
return false;
}
}
if ((getMinBufferSize() >= 0) && (dataLineInfo.getMinBufferSize() >= 0)) {
if (getMinBufferSize() < dataLineInfo.getMinBufferSize()) {
return false;
}
}
AudioFormat[] localFormats = getFormats();
if (localFormats != null) {
for (int i = 0; i < localFormats.length; i++) {
if (! (localFormats[i] == null) ) {
if (! (dataLineInfo.isFormatSupported(localFormats[i])) ) {
return false;
}
}
}
}
return true;
}
/**
* Obtains a textual description of the data line info.
* @return a string description
*/
public String toString() {
StringBuffer buf = new StringBuffer();
if ( (formats.length == 1) && (formats[0] != null) ) {
buf.append(" supporting format " + formats[0]);
} else if (getFormats().length > 1) {
buf.append(" supporting " + getFormats().length + " audio formats");
}
if ( (minBufferSize != AudioSystem.NOT_SPECIFIED) && (maxBufferSize != AudioSystem.NOT_SPECIFIED) ) {
buf.append(", and buffers of " + minBufferSize + " to " + maxBufferSize + " bytes");
} else if ( (minBufferSize != AudioSystem.NOT_SPECIFIED) && (minBufferSize > 0) ) {
buf.append(", and buffers of at least " + minBufferSize + " bytes");
} else if (maxBufferSize != AudioSystem.NOT_SPECIFIED) {
buf.append(", and buffers of up to " + minBufferSize + " bytes");
}
return new String(super.toString() + buf);
}
} // class Info
} // interface DataLine
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