JavaTM 2 Platform
Std. Ed. v1.3.1

javax.sound.sampled
Interface SourceDataLine

All Superinterfaces:
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

Inner classes inherited from class javax.sound.sampled.DataLine
DataLine.Info
 
Inner classes inherited from class javax.sound.sampled.Line
Line.Info
 
Method Summary
 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 inherited from interface javax.sound.sampled.DataLine
available, drain, flush, getBufferSize, getFormat, getFramePosition, getLevel, getMicrosecondPosition, isActive, isRunning, start, stop
 
Methods inherited from interface javax.sound.sampled.Line
addLineListener, close, getControl, getControls, getLineInfo, isControlSupported, isOpen, open, removeLineListener
 

Method Detail

open

public 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
IllegalStateException - if the line is already open
SecurityException - if the line cannot be opened due to security restrictions
See Also:
open(AudioFormat), Line.open(), Line.close(), Line.isOpen(), LineEvent

open

public 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
IllegalStateException - if the line is already open
SecurityException - if the line cannot be opened due to security restrictions
See Also:
open(AudioFormat, int), Line.open(), Line.close(), Line.isOpen(), LineEvent

write

public 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
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.
See Also:
TargetDataLine.read(byte[], int, int), DataLine.available()

JavaTM 2 Platform
Std. Ed. v1.3.1

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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