1 | package org.apollo.audio.util;
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2 |
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3 | import java.util.LinkedList;
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4 | import java.util.List;
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5 |
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6 | import org.apollo.audio.ApolloPlaybackMixer;
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7 | import org.apollo.audio.ApolloSubjectChangedEvent;
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8 | import org.apollo.mvc.Observer;
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9 | import org.apollo.mvc.Subject;
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10 | import org.apollo.mvc.SubjectChangedEvent;
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11 | import org.apollo.util.AudioMath;
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12 | import org.expeditee.gui.FrameGraphics;
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13 |
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14 | /**
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15 | * The audio playback clock ticks at {@link #CLOCK_RESOLUTION} milliseconds and
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16 | * invokes all registered clock listeners <b>on the same thread as the clock<b>.
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17 | * Thus the clock is not entiry acurrate: its intention of use is for updating
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18 | * a GUI according to the live frame position in the software mixer.
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19 | *
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20 | * Thus all thread safety precautions and efficiencies are at the users discretion.
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21 | * The ideal usage would be to simply update some data without the need of locking
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22 | * and returning asap
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23 | *
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24 | * @see {@link ApolloPlaybackMixer}
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25 | *
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26 | * @author Brook Novak
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27 | *
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28 | */
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29 | public class PlaybackClock {
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30 |
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31 | public static final long CLOCK_RESOLUTION = 300;
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32 |
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33 | private Clock clockThread = null;
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34 |
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35 | private List<PlaybackClockListener> playbackClockListeners = new LinkedList<PlaybackClockListener>();
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36 |
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37 | private static PlaybackClock instance = new PlaybackClock();
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38 | public static PlaybackClock getInstance() {
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39 | return instance;
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40 | }
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41 |
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42 | /**
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43 | * Singleton constructor preps the PlaybackClock for listening for
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44 | * audio events from the software mixer
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45 | *
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46 | */
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47 | private PlaybackClock() {
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48 |
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49 | ApolloPlaybackMixer.getInstance().addObserver(new Observer() {
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50 |
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51 | public Subject getObservedSubject() {
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52 | return ApolloPlaybackMixer.getInstance();
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53 | }
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54 | public void setObservedSubject(Subject parent) {
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55 | }
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56 |
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57 | public void modelChanged(Subject source, SubjectChangedEvent event) {
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58 |
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59 | if (event.getID() == ApolloSubjectChangedEvent.PLAYBACK_STARTED) {
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60 |
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61 | // Start the clock
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62 | assert(clockThread == null);
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63 | clockThread = new Clock();
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64 | clockThread.start();
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65 |
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66 | } else if (event.getID() == ApolloSubjectChangedEvent.PLAYBACK_STOPPED) {
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67 |
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68 | // Kill the clock
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69 | clockThread.interrupt();
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70 | clockThread = null; // it will die in its own time
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71 | }
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72 | }
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73 |
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74 | });
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75 | }
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76 |
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77 | /**
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78 | * Adds a PlaybackClockListener for receiveing notifications whenever audio is played.
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79 | *
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80 | * @param listener
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81 | * The listener to add. If already added then it won't be added again.
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82 | *
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83 | * @throws NullPointerException
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84 | * If listener is null.
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85 | */
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86 | public void addPlaybackClockListener(PlaybackClockListener listener) {
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87 | if (listener == null) throw new NullPointerException("listener");
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88 | synchronized(playbackClockListeners) {
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89 | if (!playbackClockListeners.contains(listener))
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90 | playbackClockListeners.add(listener);
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91 | }
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92 | }
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93 |
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94 | /**
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95 | * Removes a listener such that it wil stop receiving notifications.
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96 | *
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97 | * @param listener
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98 | * The listener to remove.
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99 | *
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100 | * @throws NullPointerException
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101 | * If listener is null.
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102 | */
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103 | public void removePlaybackClockListener(PlaybackClockListener listener) {
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104 | if (listener == null) throw new NullPointerException("listener");
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105 | synchronized(playbackClockListeners) {
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106 | playbackClockListeners.remove(listener);
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107 | }
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108 | }
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109 |
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110 | /**
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111 | * The clock periodically wakes and updates playback-related GUI according to the
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112 | * live position of the playback.
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113 | *
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114 | * The clock thread dies once its interupted.
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115 | *
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116 | * @author Brook Novak
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117 | *
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118 | */
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119 | private class Clock extends Thread {
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120 |
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121 | Clock() {
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122 | super("Playback Clock");
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123 | }
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124 |
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125 | public void run() {
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126 |
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127 | try {
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128 | long framePos, msPos;
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129 | boolean shouldRepaint;
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130 |
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131 | while (!interrupted()) {
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132 |
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133 | // Get the live time in frames - directly from the hardware
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134 | framePos = ApolloPlaybackMixer.getInstance().getLiveFramePosition();
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135 |
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136 | shouldRepaint = false;
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137 |
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138 | if (framePos >= 0) { // is playing still?
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139 |
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140 | msPos = AudioMath.framesToMilliseconds(
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141 | framePos,
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142 | ApolloPlaybackMixer.getInstance().getLiveAudioFormat());
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143 |
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144 | // Update the GUI. Because the clock awakes in small time slices must
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145 | // avoid updating the GUI on the swing thread: otherwise the AWT Event
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146 | // queue could easily become saturated.
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147 | synchronized(playbackClockListeners) { // arg, the most expensive operation!
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148 |
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149 | for (PlaybackClockListener listener : playbackClockListeners) {
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150 |
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151 | listener.onTick(framePos, msPos); // trusting that an exception does not occur
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152 | // If one does occur the worst that can happen is the the user doesn't
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153 | // have playback freedback.
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154 | shouldRepaint = true;
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155 | }
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156 |
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157 | }
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158 |
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159 | }
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160 |
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161 | // Do a repaint is something was listening
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162 | if (shouldRepaint) {
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163 | FrameGraphics.requestRefresh(true); // later - should not congest AWT queue
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164 | }
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165 |
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166 | sleep(CLOCK_RESOLUTION);
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167 |
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168 | } // Keep updating GUI until interupted
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169 | } catch (InterruptedException e) { // consume
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170 | // Done
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171 | }
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172 |
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173 | // Notify that have completed
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174 | synchronized(playbackClockListeners) {
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175 |
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176 | for (PlaybackClockListener listener : playbackClockListeners) {
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177 |
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178 | listener.onTick(-1, -1);
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179 |
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180 | }
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181 |
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182 | }
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183 |
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184 | }
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185 |
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186 | }
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187 |
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188 | /**
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189 | * A PlaybackClockListener is periodically notified while there is playback occuring.
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190 | *
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191 | * @author Brook Novak
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192 | *
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193 | */
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194 | public interface PlaybackClockListener {
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195 |
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196 | /**
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197 | * At every tick, this is invoked <i>directly from the clock thread</i>
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198 | *
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199 | * @see {@link PlaybackClock} for implementation considerations.
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200 | *
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201 | * @param framePosition
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202 | * The current position of the playback in frames.
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203 | * Negative if playback has finished.
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204 | *
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205 | * @param msPosition
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206 | * The current position of the playback in milliseconds.
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207 | * Negative if playback has finished.
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208 | *
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209 | */
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210 | public void onTick(long framePosition, long msPosition);
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211 |
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212 | }
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213 | }
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