1 /*
2 * Copyright (c) 1999, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation. Oracle designates this
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10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
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24 */
25
26 package javax.sound.sampled;
27
28 import java.util.Arrays;
29
30 /**
31 * {@code DataLine} adds media-related functionality to its superinterface,
32 * {@code Line}. This functionality includes transport-control methods that
33 * start, stop, drain, and flush the audio data that passes through the line. A
34 * data line can also report the current position, volume, and audio format of
35 * the media. Data lines are used for output of audio by means of the
36 * subinterfaces {@link SourceDataLine} or {@link Clip}, which allow an
37 * application program to write data. Similarly, audio input is handled by the
38 * subinterface {@link TargetDataLine}, which allows data to be read.
39 * <p>
40 * A data line has an internal buffer in which the incoming or outgoing audio
41 * data is queued. The {@link #drain()} method blocks until this internal buffer
42 * becomes empty, usually because all queued data has been processed. The
43 * {@link #flush()} method discards any available queued data from the internal
44 * buffer.
45 * <p>
46 * A data line produces {@link LineEvent.Type#START START} and
47 * {@link LineEvent.Type#STOP STOP} events whenever it begins or ceases active
48 * presentation or capture of data. These events can be generated in response to
49 * specific requests, or as a result of less direct state changes. For example,
50 * if {@link #start()} is called on an inactive data line, and data is available
51 * for capture or playback, a {@code START} event will be generated shortly,
52 * when data playback or capture actually begins. Or, if the flow of data to an
53 * active data line is constricted so that a gap occurs in the presentation of
54 * data, a {@code STOP} event is generated.
55 * <p>
56 * Mixers often support synchronized control of multiple data lines.
57 * Synchronization can be established through the {@code Mixer} interface's
58 * {@link Mixer#synchronize synchronize} method. See the description of the
59 * {@link Mixer Mixer} interface for a more complete description.
60 *
61 * @author Kara Kytle
62 * @see LineEvent
63 * @since 1.3
64 */
65 public interface DataLine extends Line {
66
67 /**
68 * Drains queued data from the line by continuing data I/O until the data
69 * line's internal buffer has been emptied. This method blocks until the
70 * draining is complete. Because this is a blocking method, it should be
71 * used with care. If {@code drain()} is invoked on a stopped line that has
72 * data in its queue, the method will block until the line is running and
73 * the data queue becomes empty. If {@code drain()} is invoked by one
74 * thread, and another continues to fill the data queue, the operation will
75 * not complete. This method always returns when the data line is closed.
76 *
77 * @see #flush()
78 */
79 void drain();
80
81 /**
82 * Flushes queued data from the line. The flushed data is discarded. In some
83 * cases, not all queued data can be discarded. For example, a mixer can
84 * flush data from the buffer for a specific input line, but any unplayed
85 * data already in the output buffer (the result of the mix) will still be
86 * played. You can invoke this method after pausing a line (the normal case)
87 * if you want to skip the "stale" data when you restart playback or
88 * capture. (It is legal to flush a line that is not stopped, but doing so
89 * on an active line is likely to cause a discontinuity in the data,
90 * resulting in a perceptible click.)
91 *
92 * @see #stop()
93 * @see #drain()
94 */
95 void flush();
96
97 /**
98 * Allows a line to engage in data I/O. If invoked on a line that is already
99 * running, this method does nothing. Unless the data in the buffer has been
100 * flushed, the line resumes I/O starting with the first frame that was
101 * unprocessed at the time the line was stopped. When audio capture or
102 * playback starts, a {@link LineEvent.Type#START START} event is generated.
103 *
104 * @see #stop()
105 * @see #isRunning()
106 * @see LineEvent
107 */
108 void start();
109
110 /**
111 * Stops the line. A stopped line should cease I/O activity. If the line is
112 * open and running, however, it should retain the resources required to
113 * resume activity. A stopped line should retain any audio data in its
114 * buffer instead of discarding it, so that upon resumption the I/O can
115 * continue where it left off, if possible. (This doesn't guarantee that
116 * there will never be discontinuities beyond the current buffer, of course;
117 * if the stopped condition continues for too long, input or output samples
118 * might be dropped.) If desired, the retained data can be discarded by
119 * invoking the {@code flush} method. When audio capture or playback stops,
120 * a {@link LineEvent.Type#STOP STOP} event is generated.
121 *
122 * @see #start()
123 * @see #isRunning()
124 * @see #flush()
125 * @see LineEvent
126 */
127 void stop();
128
129 /**
130 * Indicates whether the line is running. The default is {@code false}. An
131 * open line begins running when the first data is presented in response to
132 * an invocation of the {@code start} method, and continues until
133 * presentation ceases in response to a call to {@code stop} or because
134 * playback completes.
135 *
136 * @return {@code true} if the line is running, otherwise {@code false}
137 * @see #start()
138 * @see #stop()
139 */
140 boolean isRunning();
141
142 /**
143 * Indicates whether the line is engaging in active I/O (such as playback or
144 * capture). When an inactive line becomes active, it sends a
145 * {@link LineEvent.Type#START START} event to its listeners. Similarly,
146 * when an active line becomes inactive, it sends a
147 * {@link LineEvent.Type#STOP STOP} event.
148 *
149 * @return {@code true} if the line is actively capturing or rendering
150 * sound, otherwise {@code false}
151 * @see #isOpen
152 * @see #addLineListener
153 * @see #removeLineListener
154 * @see LineEvent
155 * @see LineListener
156 */
157 boolean isActive();
158
159 /**
160 * Obtains the current format (encoding, sample rate, number of channels,
161 * etc.) of the data line's audio data.
162 * <p>
163 * If the line is not open and has never been opened, it returns the default
164 * format. The default format is an implementation specific audio format,
165 * or, if the {@code DataLine.Info} object, which was used to retrieve this
166 * {@code DataLine}, specifies at least one fully qualified audio format,
167 * the last one will be used as the default format. Opening the line with a
168 * specific audio format (e.g. {@link SourceDataLine#open(AudioFormat)})
169 * will override the default format.
170 *
171 * @return current audio data format
172 * @see AudioFormat
173 */
174 AudioFormat getFormat();
175
176 /**
177 * Obtains the maximum number of bytes of data that will fit in the data
178 * line's internal buffer. For a source data line, this is the size of the
179 * buffer to which data can be written. For a target data line, it is the
180 * size of the buffer from which data can be read. Note that the units used
181 * are bytes, but will always correspond to an integral number of sample
182 * frames of audio data.
183 *
184 * @return the size of the buffer, in bytes
185 */
186 int getBufferSize();
187
188 /**
189 * Obtains the number of bytes of data currently available to the
190 * application for processing in the data line's internal buffer. For a
191 * source data line, this is the amount of data that can be written to the
192 * buffer without blocking. For a target data line, this is the amount of
193 * data available to be read by the application. For a clip, this value is
194 * always 0 because the audio data is loaded into the buffer when the clip
195 * is opened, and persists without modification until the clip is closed.
196 * <p>
197 * Note that the units used are bytes, but will always correspond to an
198 * integral number of sample frames of audio data.
199 * <p>
200 * An application is guaranteed that a read or write operation of up to the
201 * number of bytes returned from {@code available()} will not block;
202 * however, there is no guarantee that attempts to read or write more data
203 * will block.
204 *
205 * @return the amount of data available, in bytes
206 */
207 int available();
208
209 /**
210 * Obtains the current position in the audio data, in sample frames. The
211 * frame position measures the number of sample frames captured by, or
212 * rendered from, the line since it was opened. This return value will wrap
213 * around after 2^31 frames. It is recommended to use
214 * {@code getLongFramePosition} instead.
215 *
216 * @return the number of frames already processed since the line was opened
217 * @see #getLongFramePosition()
218 */
219 int getFramePosition();
220
221 /**
222 * Obtains the current position in the audio data, in sample frames. The
223 * frame position measures the number of sample frames captured by, or
224 * rendered from, the line since it was opened.
225 *
226 * @return the number of frames already processed since the line was opened
227 * @since 1.5
228 */
229 long getLongFramePosition();
230
231 /**
232 * Obtains the current position in the audio data, in microseconds. The
233 * microsecond position measures the time corresponding to the number of
234 * sample frames captured by, or rendered from, the line since it was
235 * opened. The level of precision is not guaranteed. For example, an
236 * implementation might calculate the microsecond position from the current
237 * frame position and the audio sample frame rate. The precision in
238 * microseconds would then be limited to the number of microseconds per
239 * sample frame.
240 *
241 * @return the number of microseconds of data processed since the line was
242 * opened
243 */
244 long getMicrosecondPosition();
245
246 /**
247 * Obtains the current volume level for the line. This level is a measure of
248 * the signal's current amplitude, and should not be confused with the
249 * current setting of a gain control. The range is from 0.0 (silence) to 1.0
250 * (maximum possible amplitude for the sound waveform). The units measure
251 * linear amplitude, not decibels.
252 *
253 * @return the current amplitude of the signal in this line, or
254 * {@link AudioSystem#NOT_SPECIFIED}
255 */
256 float getLevel();
257
258 /**
259 * Besides the class information inherited from its superclass,
260 * {@code DataLine.Info} provides additional information specific to data
261 * lines. This information includes:
262 * <ul>
263 * <li>the audio formats supported by the data line
264 * <li>the minimum and maximum sizes of its internal buffer
265 * </ul>
266 * Because a {@code Line.Info} knows the class of the line its describes, a
267 * {@code DataLine.Info} object can describe {@code DataLine} subinterfaces
268 * such as {@link SourceDataLine}, {@link TargetDataLine}, and {@link Clip}.
269 * You can query a mixer for lines of any of these types, passing an
270 * appropriate instance of {@code DataLine.Info} as the argument to a method
271 * such as {@link Mixer#getLine(Line.Info)}.
272 *
273 * @author Kara Kytle
274 * @see Line.Info
275 * @since 1.3
276 */
277 class Info extends Line.Info {
278
279 /**
280 * The set of supported formats.
281 */
282 private final AudioFormat[] formats;
283
284 /**
285 * Minimum buffer size supported by the data line, in bytes.
286 */
287 private final int minBufferSize;
288
289 /**
290 * Maximum buffer size supported by the data line, in bytes.
291 */
292 private final int maxBufferSize;
293
294 /**
295 * Constructs a data line's info object from the specified information,
296 * which includes a set of supported audio formats and a range for the
297 * buffer size. This constructor is typically used by mixer
298 * implementations when returning information about a supported line.
299 *
300 * @param lineClass the class of the data line described by the info
301 * object
302 * @param formats set of formats supported
303 * @param minBufferSize minimum buffer size supported by the data line,
304 * in bytes
305 * @param maxBufferSize maximum buffer size supported by the data line,
306 * in bytes
307 */
308 public Info(Class<?> lineClass, AudioFormat[] formats, int minBufferSize, int maxBufferSize) {
309
310 super(lineClass);
311
312 if (formats == null) {
313 this.formats = new AudioFormat[0];
314 } else {
315 this.formats = Arrays.copyOf(formats, formats.length);
316 }
317
318 this.minBufferSize = minBufferSize;
319 this.maxBufferSize = maxBufferSize;
320 }
321
322 /**
323 * Constructs a data line's info object from the specified information,
324 * which includes a single audio format and a desired buffer size. This
325 * constructor is typically used by an application to describe a desired
326 * line.
327 *
328 * @param lineClass the class of the data line described by the info
329 * object
330 * @param format desired format
331 * @param bufferSize desired buffer size, in bytes
332 */
333 public Info(Class<?> lineClass, AudioFormat format, int bufferSize) {
334
335 super(lineClass);
336
337 if (format == null) {
338 this.formats = new AudioFormat[0];
339 } else {
340 this.formats = new AudioFormat[]{format};
341 }
342
343 this.minBufferSize = bufferSize;
344 this.maxBufferSize = bufferSize;
345 }
346
347 /**
348 * Constructs a data line's info object from the specified information,
349 * which includes a single audio format. This constructor is typically
350 * used by an application to describe a desired line.
351 *
352 * @param lineClass the class of the data line described by the info
353 * object
354 * @param format desired format
355 */
356 public Info(Class<?> lineClass, AudioFormat format) {
357 this(lineClass, format, AudioSystem.NOT_SPECIFIED);
358 }
359
360 /**
361 * Obtains a set of audio formats supported by the data line. Note that
362 * {@code isFormatSupported(AudioFormat)} might return {@code true} for
363 * certain additional formats that are missing from the set returned by
364 * {@code getFormats()}. The reverse is not the case:
365 * {@code isFormatSupported(AudioFormat)} is guaranteed to return
366 * {@code true} for all formats returned by {@code getFormats()}.
367 * <p>
368 * Some fields in the {@code AudioFormat} instances can be set to
369 * {@link AudioSystem#NOT_SPECIFIED NOT_SPECIFIED} if that field does
370 * not apply to the format, or if the format supports a wide range of
371 * values for that field. For example, a multi-channel device supporting
372 * up to 64 channels, could set the channel field in the
373 * {@code AudioFormat} instances returned by this method to
374 * {@code NOT_SPECIFIED}.
375 *
376 * @return a set of supported audio formats
377 * @see #isFormatSupported(AudioFormat)
378 */
379 public AudioFormat[] getFormats() {
380 return Arrays.copyOf(formats, formats.length);
381 }
382
383 /**
384 * Indicates whether this data line supports a particular audio format.
385 * The default implementation of this method simply returns {@code true}
386 * if the specified format matches any of the supported formats.
387 *
388 * @param format the audio format for which support is queried
389 * @return {@code true} if the format is supported, otherwise
390 * {@code false}
391 * @see #getFormats
392 * @see AudioFormat#matches
393 */
394 public boolean isFormatSupported(AudioFormat format) {
395
396 for (int i = 0; i < formats.length; i++) {
397 if (format.matches(formats[i])) {
398 return true;
399 }
400 }
401
402 return false;
403 }
404
405 /**
406 * Obtains the minimum buffer size supported by the data line.
407 *
408 * @return minimum buffer size in bytes, or
409 * {@code AudioSystem.NOT_SPECIFIED}
410 */
411 public int getMinBufferSize() {
412 return minBufferSize;
413 }
414
415 /**
416 * Obtains the maximum buffer size supported by the data line.
417 *
418 * @return maximum buffer size in bytes, or
419 * {@code AudioSystem.NOT_SPECIFIED}
420 */
421 public int getMaxBufferSize() {
422 return maxBufferSize;
423 }
424
425 /**
426 * Determines whether the specified info object matches this one. To
427 * match, the superclass match requirements must be met. In addition,
428 * this object's minimum buffer size must be at least as large as that
429 * of the object specified, its maximum buffer size must be at most as
430 * large as that of the object specified, and all of its formats must
431 * match formats supported by the object specified.
432 *
433 * @param info the info object which is being compared to this one
434 * @return {@code true} if this object matches the one specified,
435 * otherwise {@code false}
436 */
437 @Override
438 public boolean matches(Line.Info info) {
439
440 if (! (super.matches(info)) ) {
441 return false;
442 }
443
444 Info dataLineInfo = (Info)info;
445
446 // treat anything < 0 as NOT_SPECIFIED
447 // demo code in old Java Sound Demo used a wrong buffer calculation
448 // that would lead to arbitrary negative values
449 if ((getMaxBufferSize() >= 0) && (dataLineInfo.getMaxBufferSize() >= 0)) {
450 if (getMaxBufferSize() > dataLineInfo.getMaxBufferSize()) {
451 return false;
452 }
453 }
454
455 if ((getMinBufferSize() >= 0) && (dataLineInfo.getMinBufferSize() >= 0)) {
456 if (getMinBufferSize() < dataLineInfo.getMinBufferSize()) {
457 return false;
458 }
459 }
460
461 AudioFormat[] localFormats = getFormats();
462
463 if (localFormats != null) {
464
465 for (int i = 0; i < localFormats.length; i++) {
466 if (! (localFormats[i] == null) ) {
467 if (! (dataLineInfo.isFormatSupported(localFormats[i])) ) {
468 return false;
469 }
470 }
471 }
472 }
473
474 return true;
475 }
476
477 /**
478 * Obtains a textual description of the data line info.
479 *
480 * @return a string description
481 */
482 @Override
483 public String toString() {
484
485 StringBuilder sb = new StringBuilder();
486
487 if ( (formats.length == 1) && (formats[0] != null) ) {
488 sb.append(" supporting format " + formats[0]);
489 } else if (getFormats().length > 1) {
490 sb.append(" supporting " + getFormats().length + " audio formats");
491 }
492
493 if ( (minBufferSize != AudioSystem.NOT_SPECIFIED) && (maxBufferSize != AudioSystem.NOT_SPECIFIED) ) {
494 sb.append(", and buffers of " + minBufferSize + " to " + maxBufferSize + " bytes");
495 } else if ( (minBufferSize != AudioSystem.NOT_SPECIFIED) && (minBufferSize > 0) ) {
496 sb.append(", and buffers of at least " + minBufferSize + " bytes");
497 } else if (maxBufferSize != AudioSystem.NOT_SPECIFIED) {
498 sb.append(", and buffers of up to " + minBufferSize + " bytes");
499 }
500
501 return new String(super.toString() + sb);
502 }
503 }
504 }