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package javax.sound.sampled;


A target data line is a type of 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 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. 
Author:Kara Kytle
See Also:
Since:1.3
/**
 * A target data line is a type of {@link 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.)
 * <p>
 * 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.
 * <p>
 * The target data line can be obtained from a mixer by invoking the
 * {@link Mixer#getLine getLine} method of {@code Mixer} with an appropriate
 * {@link DataLine.Info} object.
 * <p>
 * The {@code 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
 * {@link DataLine#available available} method defined in the {@code 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.
 *
 * @author Kara Kytle
 * @see Mixer
 * @see DataLine
 * @see SourceDataLine
 * @since 1.3
 */
public interface TargetDataLine extends DataLine {

    
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 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. 
Params:
  • format – the desired audio format
  • bufferSize – the desired buffer size, in bytes
Throws:
See Also:
/**
     * Opens the line with the specified format and requested buffer size,
     * causing the line to acquire any required system resources and become
     * operational.
     * <p>
     * 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
     * {@code 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 {@link DataLine#getBufferSize}
     * <p>
     * If this operation succeeds, the line is marked as open, and an
     * {@link LineEvent.Type#OPEN OPEN} event is dispatched to the line's
     * listeners.
     * <p>
     * Invoking this method on a line that is already open is illegal and may
     * result in an {@code IllegalStateException}.
     * <p>
     * Some lines, once closed, cannot be reopened. Attempts to reopen such a
     * line will always result in a {@code LineUnavailableException}.
     *
     * @param  format the desired audio format
     * @param  bufferSize the desired buffer size, in bytes
     * @throws LineUnavailableException if the line cannot be opened due to
     *         resource restrictions
     * @throws IllegalArgumentException if the buffer size does not represent an
     *         integral number of sample frames, or if {@code format} is not
     *         fully specified or invalid
     * @throws IllegalStateException if the line is already open
     * @throws SecurityException if the line cannot be opened due to security
     *         restrictions
     * @see #open(AudioFormat)
     * @see Line#open
     * @see Line#close
     * @see Line#isOpen
     * @see LineEvent
     */
    void open(AudioFormat format, int bufferSize) 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 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. 
Params:
  • format – the desired audio format
Throws:
See Also:
/**
     * Opens the line with the specified format, causing the line to acquire any
     * required system resources and become operational.
     * <p>
     * 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
     * {@link DataLine#getBufferSize}
     * <p>
     * If this operation succeeds, the line is marked as open, and an
     * {@link LineEvent.Type#OPEN OPEN} event is dispatched to the line's
     * listeners.
     * <p>
     * Invoking this method on a line that is already open is illegal and may
     * result in an {@code IllegalStateException}.
     * <p>
     * Some lines, once closed, cannot be reopened. Attempts to reopen such a
     * line will always result in a {@code LineUnavailableException}.
     *
     * @param  format the desired audio format
     * @throws LineUnavailableException if the line cannot be opened due to
     *         resource restrictions
     * @throws IllegalArgumentException if {@code format} is not fully specified
     *         or invalid
     * @throws IllegalStateException if the line is already open
     * @throws SecurityException if the line cannot be opened due to security
     *         restrictions
     * @see #open(AudioFormat, int)
     * @see Line#open
     * @see Line#close
     * @see Line#isOpen
     * @see LineEvent
     */
    void open(AudioFormat format) throws LineUnavailableException;

    
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 the DataLine 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.

Params:
  • b – a byte array that will contain the requested input data when
        this method returns
  • off – the offset from the beginning of the array, in bytes
  • len – the requested number of bytes to read
Throws:
See Also:
Returns:the number of bytes actually read
/**
     * 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.
     * <p>
     * The number of bytes that can be read without blocking can be ascertained
     * using the {@link DataLine#available available} method of the
     * {@code DataLine} 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.)
     * <p>
     * The number of bytes to be read must represent an integral number of
     * sample frames, such that:
     * <p style="text-align:center">
     * {@code [ bytes read ] % [frame size in bytes ] == 0}
     * <p>
     * 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.
     *
     * @param  b a byte array that will contain the requested input data when
     *         this method returns
     * @param  off the offset from the beginning of the array, in bytes
     * @param  len the requested number of bytes to read
     * @return the number of bytes actually read
     * @throws IllegalArgumentException if the requested number of bytes does
     *         not represent an integral number of sample frames, or if
     *         {@code len} is negative
     * @throws ArrayIndexOutOfBoundsException if {@code off} is negative, or
     *         {@code off+len} is greater than the length of the array {@code b}
     *
     * @see SourceDataLine#write
     * @see DataLine#available
     */
    int read(byte[] b, int off, int len);

    /**
     * Obtains the number of sample frames of audio data that can be read from
     * the target data line without blocking. Note that the return value
     * measures sample frames, not bytes.
     *
     * @return the number of sample frames currently available for reading
     * @see SourceDataLine#availableWrite
     */
    //public int availableRead();
}