Interface TargetDataLine
- All Superinterfaces:
AutoCloseable, DataLine, Line
DataLine
from which audio data can be
read. The most common example is a data line that gets its data from an audio
capture device. (The device is implemented as a mixer that writes to the
target data line.)
Note that the naming convention for this interface reflects the relationship between the line and its mixer. From the perspective of an application, a target data line may act as a source for audio data.
The target data line can be obtained from a mixer by invoking the
getLine
method of Mixer
with an appropriate
DataLine.Info
object.
The TargetDataLine
interface provides a method for reading the
captured data from the target data line's buffer. Applications that record
audio should read data from the target data line quickly enough to keep the
buffer from overflowing, which could cause discontinuities in the captured
data 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. If the buffer does overflow, the oldest queued data is discarded and
replaced by new data.
- Since:
- 1.3
- See Also:
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Nested Class Summary
Nested classes/interfaces declared in interface DataLine
DataLine.Info
Modifier and TypeInterfaceDescriptionstatic class
Besides the class information inherited from its superclass,DataLine.Info
provides additional information specific to data lines. -
Method Summary
Modifier and TypeMethodDescriptionvoid
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 requested buffer size, causing the line to acquire any required system resources and become operational.int
read
(byte[] b, int off, int len) Reads audio data from the data line's input buffer.Methods declared in interface DataLine
available, drain, flush, getBufferSize, getFormat, getFramePosition, getLevel, getLongFramePosition, getMicrosecondPosition, isActive, isRunning, start, stop
Modifier and TypeMethodDescriptionint
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
Obtains the maximum number of bytes of data that will fit in the data line's internal buffer.Obtains the current format (encoding, sample rate, number of channels, etc.) of the data line's audio data.int
Obtains the current position in the audio data, in sample frames.float
getLevel()
Obtains the current volume level for the line.long
Obtains the current position in the audio data, in sample frames.long
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
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 TypeMethodDescriptionvoid
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.getControl
(Control.Type control) Obtains a control of the specified type, if there is any.Control[]
Obtains the set of controls associated with this line.Obtains theLine.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.
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Method Details
-
open
Opens the line with the specified format and requested 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 callingDataLine.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 that is already open is illegal and may result in an
IllegalStateException
.Some lines, once closed, cannot be reopened. Attempts to reopen such a line will always result in a
LineUnavailableException
.- Parameters:
format
- the desired audio formatbufferSize
- the desired buffer size, in bytes- Throws:
LineUnavailableException
- if the line cannot be opened due to resource restrictionsIllegalArgumentException
- if the buffer size does not represent an integral number of sample frames, or ifformat
is not fully specified or invalidIllegalStateException
- if the line is already open- See Also:
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open
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 that is already open is illegal and may result in an
IllegalStateException
.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 restrictionsIllegalArgumentException
- ifformat
is not fully specified or invalidIllegalStateException
- if the line is already open- See Also:
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read
int read(byte[] b, int off, int len) Reads audio data from the data line's input buffer. The requested number of bytes is read into the specified array, starting at the specified offset into the array in bytes. This method blocks until the requested amount of data has been read. However, if the data line is closed, stopped, drained, or flushed before the requested amount has been read, the method no longer blocks, but returns the number of bytes read thus far.The number of bytes that can be read without blocking can be ascertained using the
available
method of theDataLine
interface. (While it is guaranteed that this number of bytes can be read without blocking, there is no guarantee that attempts to read additional data will block.)The number of bytes to be read must represent an integral number of sample frames, such that:
[ bytes read ] % [frame size in bytes ] == 0
The return value will always meet this requirement. A request to read 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 that will contain the requested input data when this method returnsoff
- the offset from the beginning of the array, in byteslen
- the requested number of bytes to read- Returns:
- the number of bytes actually read
- Throws:
IllegalArgumentException
- if the requested number of bytes does not represent an integral number of sample frames, or iflen
is negativeArrayIndexOutOfBoundsException
- ifoff
is negative, oroff+len
is greater than the length of the arrayb
- See Also:
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