Interface SourceDataLine

All Superinterfaces:

AutoCloseable, DataLine, Line

public interface SourceDataLine
extends DataLine

A source data line is a data line to which data may be written. It acts as a source to its mixer. An application writes audio bytes to a source data line, which handles the buffering of the bytes and delivers them to the mixer. The mixer may mix the samples with those from other sources and then deliver the mix to a target such as an output port (which may represent an audio output device on a sound card).

Note that the naming convention for this interface reflects the relationship between the line and its mixer. From the perspective of an application, a source data line may act as a target for audio data.

A source data line can be obtained from a mixer by invoking the getLine method of Mixer with an appropriate DataLine.Info object.

The SourceDataLine interface provides a method for writing audio data to the data line's buffer. Applications that play or mix audio should write data to the source data line quickly enough to keep the buffer from underflowing (emptying), which could cause discontinuities in the audio that are perceived as clicks. Applications can use the available method defined in the DataLine interface to determine the amount of data currently queued in the data line's buffer. The amount of data which can be written to the buffer without blocking is the difference between the buffer size and the amount of queued data. If the delivery of audio output stops due to underflow, a STOP event is generated. A START event is generated when the audio output resumes.

Since:

1.3

See Also:

• Mixer
• DataLine
• TargetDataLine

Nested Class Summary

Nested classes/interfaces declared in interface DataLine

DataLine.Info

Modifier and Type	Interface	Description
static class	DataLine.Info	Besides the class information inherited from its superclass, DataLine.Info provides additional information specific to data lines.

Method Summary

Modifier and Type	Method	Description
void	open(AudioFormat format)	Opens the line with the specified format, causing the line to acquire any required system resources and become operational.
void	open(AudioFormat format, int bufferSize)	Opens the line with the specified format and suggested buffer size, causing the line to acquire any required system resources and become operational.
int	write(byte[] b, int off, int len)	Writes audio data to the mixer via this source data line.

Methods declared in interface DataLine

available, drain, flush, getBufferSize, getFormat, getFramePosition, getLevel, getLongFramePosition, getMicrosecondPosition, isActive, isRunning, start, stop

Modifier and Type	Method	Description
int	available()	Obtains the number of bytes of data currently available to the application for processing in the data line's internal buffer.
void	drain()	Drains queued data from the line by continuing data I/O until the data line's internal buffer has been emptied.
void	flush()	Flushes queued data from the line.
int	getBufferSize()	Obtains the maximum number of bytes of data that will fit in the data line's internal buffer.
AudioFormat	getFormat()	Obtains the current format (encoding, sample rate, number of channels, etc.) of the data line's audio data.
int	getFramePosition()	Obtains the current position in the audio data, in sample frames.
float	getLevel()	Obtains the current volume level for the line.
long	getLongFramePosition()	Obtains the current position in the audio data, in sample frames.
long	getMicrosecondPosition()	Obtains the current position in the audio data, in microseconds.
boolean	isActive()	Indicates whether the line is engaging in active I/O (such as playback or capture).
boolean	isRunning()	Indicates whether the line is running.
void	start()	Allows a line to engage in data I/O.
void	stop()	Stops the line.

Methods declared in interface Line

addLineListener, close, getControl, getControls, getLineInfo, isControlSupported, isOpen, open, removeLineListener

Modifier and Type	Method	Description
void	addLineListener(LineListener listener)	Adds a listener to this line.
void	close()	Closes the line, indicating that any system resources in use by the line can be released.
Control	getControl(Control.Type control)	Obtains a control of the specified type, if there is any.
Control[]	getControls()	Obtains the set of controls associated with this line.
Line.Info	getLineInfo()	Obtains the Line.Info object describing this line.
boolean	isControlSupported(Control.Type control)	Indicates whether the line supports a control of the specified type.
boolean	isOpen()	Indicates whether the line is open, meaning that it has reserved system resources and is operational, although it might not currently be playing or capturing sound.
void	open()	Opens the line, indicating that it should acquire any required system resources and become operational.
void	removeLineListener(LineListener listener)	Removes the specified listener from this line's list of listeners.

Method Details

open

void open(AudioFormat format,
 int bufferSize)
   throws LineUnavailableException

Opens the line with the specified format and suggested buffer size, causing the line to acquire any required system resources and become operational.

The buffer size is specified in bytes, but must represent an integral number of sample frames. Invoking this method with a requested buffer size that does not meet this requirement may result in an IllegalArgumentException. The actual buffer size for the open line may differ from the requested buffer size. The value actually set may be queried by subsequently calling DataLine.getBufferSize().

If this operation succeeds, the line is marked as open, and an OPEN event is dispatched to the line's listeners.

Invoking this method on a line which is already open is illegal and may result in an IllegalStateException.

Note that some lines, once closed, cannot be reopened. Attempts to reopen such a line will always result in a LineUnavailableException.

Parameters:

format - the desired audio format

bufferSize - the desired buffer size

Throws:

LineUnavailableException - if the line cannot be opened due to resource restrictions

IllegalArgumentException - if the buffer size does not represent an integral number of sample frames, or if format is not fully specified or invalid

IllegalStateException - if the line is already open

See Also:

• open(AudioFormat)
• Line.open()
• Line.close()
• Line.isOpen()
• LineEvent

open

void open(AudioFormat format)
   throws LineUnavailableException

Opens the line with the specified format, causing the line to acquire any required system resources and become operational.

The implementation chooses a buffer size, which is measured in bytes but which encompasses an integral number of sample frames. The buffer size that the system has chosen may be queried by subsequently calling DataLine.getBufferSize().

If this operation succeeds, the line is marked as open, and an OPEN event is dispatched to the line's listeners.

Invoking this method on a line which is already open is illegal and may result in an IllegalStateException.

Note that some lines, once closed, cannot be reopened. Attempts to reopen such a line will always result in a LineUnavailableException.

Parameters:

format - the desired audio format

Throws:

LineUnavailableException - if the line cannot be opened due to resource restrictions

IllegalArgumentException - if format is not fully specified or invalid

IllegalStateException - if the line is already open

See Also:

• open(AudioFormat, int)
• Line.open()
• Line.close()
• Line.isOpen()
• LineEvent

write

int write(byte[] b,
 int off,
 int len)

Writes audio data to the mixer via this source data line. The requested number of bytes of data are read from the specified array, starting at the given offset into the array, and written to the data line's buffer. If the caller attempts to write more data than can currently be written (see available), this method blocks until the requested amount of data has been written. This applies even if the requested amount of data to write is greater than the data line's buffer size. However, if the data line is closed, stopped, or flushed before the requested amount has been written, the method no longer blocks, but returns the number of bytes written thus far.

The number of bytes that can be written without blocking can be ascertained using the available method of the DataLine interface. (While it is guaranteed that this number of bytes can be written without blocking, there is no guarantee that attempts to write additional data will block.)

The number of bytes to write must represent an integral number of sample frames, such that:

[ bytes written ] % [frame size in bytes ] == 0

The return value will always meet this requirement. A request to write a number of bytes representing a non-integral number of sample frames cannot be fulfilled and may result in an IllegalArgumentException.

Parameters:

b - a byte array containing data to be written to the data line

off - the offset from the beginning of the array, in bytes

len - the length, in bytes, of the valid data in the array (in other words, the requested amount of data to write, in bytes)

Returns:

the number of bytes actually written

Throws:

IllegalArgumentException - if the requested number of bytes does not represent an integral number of sample frames, or if len is negative

ArrayIndexOutOfBoundsException - if off is negative, or off+len is greater than the length of the array b

See Also:

• TargetDataLine.read(byte[], int, int)
• DataLine.available()