SourceDataLine


1   /*
2    * @(#)SourceDataLine.java  1.20 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package javax.sound.sampled;    
9   
10  
11  /**
12   * A source data line is a data line to which data may be written.  It acts as
13   * a source to its mixer. An application writes audio bytes to a source data line,
14   * which handles the buffering of the bytes and delivers them to the mixer.
15   * The mixer may mix the samples with those from other sources and then deliver
16   * the mix to a target such as an output port (which may represent an audio output    
17   * device on a sound card).
18   * <p>
19   * Note that the naming convention for this interface reflects the relationship
20   * between the line and its mixer.  From the perspective of an application,
21   * a source data line may act as a target for audio data.
22   * <p>
23   * A source data line can be obtained from a mixer by invoking the 
24   * <code>{@link Mixer#getLine getLine}</code> method of <code>Mixer</code> with 
25   * an appropriate <code>{@link DataLine.Info}</code> object.
26   * <p>
27   * The <code>SourceDataLine</code> interface provides a method for writing 
28   * audio data to the data line's buffer. Applications that play or mix 
29   * audio should write data to the source data line quickly enough to keep the 
30   * buffer from underflowing (emptying), which could cause discontinuities in 
31   * the audio that are perceived as clicks.  Applications can use the 
32   * <code>{@link DataLine#available available}</code> method defined in the
33   * <code>DataLine</code> interface to determine the amount of data currently
34   * queued in the data line's buffer.  The amount of data which can be written
35   * to the buffer without blocking is the difference between the buffer size
36   * and the amount of queued data.  If the delivery of audio output 
37   * stops due to underflow, a <code>{@link LineEvent.Type#STOP STOP}</code> event is 
38   * generated.  A <code>{@link LineEvent.Type#START START}</code> event is generated
39   * when the audio output resumes. 
40   *
41   * @author Kara Kytle
42   * @version 1.20 03/12/19
43   * @see Mixer
44   * @see DataLine
45   * @see TargetDataLine
46   * @since 1.3
47   */
48  public interface SourceDataLine extends DataLine   {
49      
50  
51      /**
52       * Opens the line with the specified format and suggested buffer size,
53       * causing the line to acquire any required
54       * system resources and become operational.
55       * <p>
56       * The buffer size is specified in bytes, but must represent an integral 
57       * number of sample frames.  Invoking this method with a requested buffer 
58       * size that does not meet this requirement may result in an 
59       * IllegalArgumentException.  The actual buffer size for the open line may 
60       * differ from the requested buffer size.  The value actually set may be 
61       * queried by subsequently calling <code>{@link DataLine#getBufferSize}</code>.  
62       * <p>
63       * If this operation succeeds, the line is marked as open, and an 
64       * <code>{@link LineEvent.Type#OPEN OPEN}</code> event is dispatched to the 
65       * line's listeners.
66       * <p>
67       * Invoking this method on a line which is already open is illegal
68       * and may result in an <code>IllegalStateException</code>.
69       * <p>
70       * Note that some lines, once closed, cannot be reopened.  Attempts
71       * to reopen such a line will always result in a 
72       * <code>LineUnavailableException</code>.
73       *
74       * @param format the desired audio format
75       * @param bufferSize the desired buffer size
76       * @throws LineUnavailableException if the line cannot be
77       * opened due to resource restrictions
78       * @throws IllegalArgumentException if the buffer size does not represent
79       * an integral number of sample frames,
80       * or if <code>format</code> is not fully specified or invalid
81       * @throws IllegalStateException if the line is already open
82       * @throws SecurityException if the line cannot be
83       * opened due to security restrictions
84       *
85       * @see #open(AudioFormat)
86       * @see Line#open
87       * @see Line#close
88       * @see Line#isOpen
89       * @see LineEvent
90       */
91      public void open(AudioFormat   format, int bufferSize) throws LineUnavailableException  ;
92  
93  
94      /**
95       * Opens the line with the specified format, causing the line to acquire any 
96       * required system resources and become operational.  
97       *   
98       * <p>
99       * The implementation chooses a buffer size, which is measured in bytes but 
100      * which encompasses an integral number of sample frames.  The buffer size 
101      * that the system has chosen may be queried by subsequently calling 
102      * <code>{@link DataLine#getBufferSize}</code>.
103      * <p>
104      * If this operation succeeds, the line is marked as open, and an 
105      * <code>{@link LineEvent.Type#OPEN OPEN}</code> event is dispatched to the 
106      * line's listeners.
107      * <p>
108      * Invoking this method on a line which is already open is illegal
109      * and may result in an <code>IllegalStateException</code>.
110      * <p>
111      * Note that some lines, once closed, cannot be reopened.  Attempts
112      * to reopen such a line will always result in a 
113      * <code>LineUnavailableException</code>.
114      *
115      * @param format the desired audio format
116      * @throws LineUnavailableException if the line cannot be
117      * opened due to resource restrictions
118      * @throws IllegalArgumentException if <code>format</code>
119      * is not fully specified or invalid
120      * @throws IllegalStateException if the line is already open
121      * @throws SecurityException if the line cannot be
122      * opened due to security restrictions
123      *
124      * @see #open(AudioFormat, int)
125      * @see Line#open
126      * @see Line#close
127      * @see Line#isOpen
128      * @see LineEvent
129      */
130     public void open(AudioFormat   format) throws LineUnavailableException  ;
131 
132 
133     /**
134      * Writes audio data to the mixer via this source data line.  The requested 
135      * number of bytes of data are read from the specified array, 
136      * starting at the given offset into the array, and written to the data 
137      * line's buffer.  If the caller attempts to write more data than can 
138      * currently be written (see <code>{@link DataLine#available available}</code>), 
139      * this method blocks until the requested amount of data has been written.  
140      * This applies even if the requested amount of data to write is greater 
141      * than the data line's buffer size.  However, if the data line is closed, 
142      * stopped, or flushed before the requested amount has been written,
143      * the method no longer blocks, but returns the number of bytes 
144      * written thus far. 
145      * <p>
146      * The number of bytes that can be written without blocking can be ascertained
147      * using the <code>{@link DataLine#available available}</code> method of the
148      * <code>DataLine</code> interface.  (While it is guaranteed that
149      * this number of bytes can be written without blocking, there is no guarantee
150      * that attempts to write additional data will block.)
151      * <p>
152      * The number of bytes to write must represent an integral number of
153      * sample frames, such that:
154      * <br>
155      * <center><code>[ bytes written ] % [frame size in bytes ] == 0</code></center>
156      * <br>
157      * The return value will always meet this requirement.  A request to write a 
158      * number of bytes representing a non-integral number of sample frames cannot 
159      * be fulfilled and may result in an <code>IllegalArgumentException</code>.
160      *
161      * @param b a byte array containing data to be written to the data line
162      * @param len the length, in bytes, of the valid data in the array 
163      * (in other words, the requested amount of data to write, in bytes)
164      * @param off the offset from the beginning of the array, in bytes
165      * @return the number of bytes actually written
166      * @throws IllegalArgumentException if the requested number of bytes does
167      * not represent an integral number of sample frames,
168      * or if <code>len</code> is negative
169      * @throws ArrayIndexOutOfBoundsException if <code>off</code> is negative,
170      * or <code>off+len</code> is greater than the length of the array
171      * <code>b</code>.
172      *
173      * @see TargetDataLine#read
174      * @see DataLine#available
175      */ 
176     public int write(byte[] b, int off, int len);
177 
178     /**
179      * Obtains the number of sample frames of audio data that can be written to 
180      * the mixer, via this data line, without blocking.  Note that the return 
181      * value measures sample frames, not bytes. 
182      * @return the number of sample frames currently available for writing
183      * @see TargetDataLine#availableRead
184      */
185     //public int availableWrite();
186 }
187
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