Time stretching, AndroidX, update gradle

LICENSE

@@ -19,3 +19,211 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
+
+==============================================================================
+
+This software includes the sonic library which is licensed under the Apache
+License, Version 2.0.
+
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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android/build.gradle

@@ -8,7 +8,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.2.1'
+        classpath 'com.android.tools.build:gradle:3.5.0'
     }
 }
 
@@ -25,10 +25,16 @@ android {
     compileSdkVersion 28
 
     defaultConfig {
-        minSdkVersion 16
+        minSdkVersion 21
-        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
+
     lintOptions {
         disable 'InvalidPackage'
     }
+
+    compileOptions {
+        sourceCompatibility 1.8
+        targetCompatibility 1.8
+    }
 }

android/gradle.properties

@@ -1,2 +1,4 @@
 org.gradle.jvmargs=-Xmx1536M
-
+android.enableR8=true
+android.useAndroidX=true
+android.enableJetifier=true

android/src/main/java/com/ryanheise/just_audio/AudioPlayer.java

@@ -1,26 +1,35 @@
 package com.ryanheise.just_audio;
 
-import android.media.MediaPlayer;
+import android.media.AudioFormat;
+import android.media.AudioManager;
+import android.media.AudioTrack;
+import android.media.MediaCodec;
+import android.media.MediaExtractor;
+import android.media.MediaFormat;
 import android.media.MediaTimestamp;
+import android.os.Handler;
 import io.flutter.plugin.common.EventChannel;
 import io.flutter.plugin.common.EventChannel.EventSink;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
 import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
 import io.flutter.plugin.common.MethodChannel.Result;
-import java.util.List;
-import java.io.IOException;
-import android.os.Handler;
-import java.util.ArrayList;
 import io.flutter.plugin.common.PluginRegistry.Registrar;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Deque;
+import java.util.LinkedList;
+import java.util.List;
+import sonic.Sonic;
 
-public class AudioPlayer implements MethodCallHandler, MediaPlayer.OnCompletionListener {
+public class AudioPlayer implements MethodCallHandler {
 	private final Registrar registrar;
 	private final MethodChannel methodChannel;
 	private final EventChannel eventChannel;
 	private EventSink eventSink;
 	private final Handler handler = new Handler();
-	private Runnable endDetector;
 	private final Runnable positionObserver = new Runnable() {
 		@Override
 		public void run() {
@@ -35,14 +44,31 @@ public class AudioPlayer implements MethodCallHandler, MediaPlayer.OnCompletionL
 	};
 
 	private final String id;
-	private final MediaPlayer player;
+	private String url;
-	private PlaybackState state;
+	private volatile PlaybackState state;
 	private PlaybackState stateBeforeSeek;
 	private long updateTime;
 	private int updatePosition;
-	private Integer seekPos;
+	private Deque<SeekRequest> seekRequests = new LinkedList<>();
+
+	private MediaExtractor extractor;
+	private MediaFormat format;
+	private Sonic sonic;
+	private int channelCount;
+	private int sampleRate;
+	private int duration;
+	private MediaCodec codec;
+	private AudioTrack audioTrack;
+	private PlayThread playThread;
+	private int start;
+	private Integer untilPosition;
+	private Object monitor = new Object();
+	private float volume = 1.0f;
+	private float speed = 1.0f;
+	private Thread mainThread;
 
 	public AudioPlayer(final Registrar registrar, final String id) {
+		mainThread = Thread.currentThread();
 		this.registrar = registrar;
 		this.id = id;
 		methodChannel = new MethodChannel(registrar.messenger(), "com.ryanheise.just_audio.methods." + id);
@@ -60,34 +86,25 @@ public class AudioPlayer implements MethodCallHandler, MediaPlayer.OnCompletionL
 			}
 		});
 		state = PlaybackState.none;
-		player = new MediaPlayer();
-		player.setOnCompletionListener(this);
 	}
 
 	private void checkForDiscontinuity() {
-		// TODO: Consider using player.setOnMediaTimeDiscontinuityListener()
-		// when available in SDK. (Added in API level 28)
 		final long now = System.currentTimeMillis();
 		final int position = getCurrentPosition();
 		final long timeSinceLastUpdate = now - updateTime;
-		final long expectedPosition = updatePosition + timeSinceLastUpdate;
+		final long expectedPosition = updatePosition + (long)(timeSinceLastUpdate * speed);
 		final long drift = position - expectedPosition;
 		// Update if we've drifted or just started observing
 		if (updateTime == 0L) {
 			broadcastPlayerState();
 		} else if (drift < -100) {
 			System.out.println("time discontinuity detected: " + drift);
-			setPlaybackState(PlaybackState.buffering);
+			transition(PlaybackState.buffering);
 		} else if (state == PlaybackState.buffering) {
-			setPlaybackState(PlaybackState.playing);
+			transition(PlaybackState.playing);
 		}
 	}
 
-	@Override
-	public void onCompletion(final MediaPlayer mp) {
-		setPlaybackState(PlaybackState.stopped);
-	}
-
 	@Override
 	public void onMethodCall(final MethodCall call, final Result result) {
 		final List<?> args = (List<?>)call.arguments;
@@ -105,11 +122,14 @@ public class AudioPlayer implements MethodCallHandler, MediaPlayer.OnCompletionL
 				result.success(null);
 				break;
 			case "stop":
-				stop();
+				stop(result);
-				result.success(null);
 				break;
 			case "setVolume":
-				setVolume((Double)args.get(0));
+				setVolume((float)((double)((Double)args.get(0))));
+				result.success(null);
+				break;
+			case "setSpeed":
+				setSpeed((float)((double)((Double)args.get(0))));
 				result.success(null);
 				break;
 			case "seek":
@@ -125,20 +145,17 @@ public class AudioPlayer implements MethodCallHandler, MediaPlayer.OnCompletionL
 			}
 		} catch (IllegalStateException e) {
 			e.printStackTrace();
-			result.error("Illegal state", null, null);
+			result.error("Illegal state: " + e.getMessage(), null, null);
 		} catch (Exception e) {
 			e.printStackTrace();
-			result.error("Error", null, null);
+			result.error("Error: " + e, null, null);
 		}
 	}
 
 	private void broadcastPlayerState() {
 		final ArrayList<Object> event = new ArrayList<Object>();
-		// state
 		event.add(state.ordinal());
-		// updatePosition
 		event.add(updatePosition = getCurrentPosition());
-		// updateTime
 		event.add(updateTime = System.currentTimeMillis());
 		eventSink.success(event);
 	}
@@ -146,101 +163,243 @@ public class AudioPlayer implements MethodCallHandler, MediaPlayer.OnCompletionL
 	private int getCurrentPosition() {
 		if (state == PlaybackState.none || state == PlaybackState.connecting) {
 			return 0;
-		} else if (seekPos != null) {
+		} else if (seekRequests.size() > 0) {
-			return seekPos;
+			return seekRequests.peekFirst().pos;
 		} else {
-			return player.getCurrentPosition();
+			return (int)(extractor.getSampleTime() / 1000);
 		}
 	}
 
-	private void setPlaybackState(final PlaybackState state) {
+	private void transition(final PlaybackState newState) {
-		final PlaybackState oldState = this.state;
+		transition(state, newState);
-		this.state = state;
+	}
-		if (oldState != PlaybackState.playing && state == PlaybackState.playing) {
+
+	private void transition(final PlaybackState oldState, final PlaybackState newState) {
+		state = newState;
+		if (oldState != PlaybackState.playing && newState == PlaybackState.playing) {
 			startObservingPosition();
 		}
 		broadcastPlayerState();
 	}
 
-	public void setUrl(final String url, final Result result) throws IOException {
+	private void bgTransition(final PlaybackState newState) {
-		setPlaybackState(PlaybackState.connecting);
+		bgTransition(state, newState);
-		player.reset();
+	}
-		player.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
+
+	private void bgTransition(final PlaybackState oldState, final PlaybackState newState) {
+		// Redundant assignment which ensures the state is set
+		// immediately in the background thread.
+		state = newState;
+		handler.post(new Runnable() {
 			@Override
-			public void onPrepared(final MediaPlayer mp) {
+			public void run() {
-				setPlaybackState(PlaybackState.stopped);
+				transition(oldState, newState);
-				result.success(mp.getDuration());
 			}
 		});
-		player.setDataSource(url);
+	}
-		player.prepareAsync();
+
+	public void setUrl(final String url, final Result result) throws IOException {
+		if (state != PlaybackState.none && state != PlaybackState.stopped) {
+			throw new IllegalStateException("Can call setUrl only from none and stopped states");
+		}
+		transition(PlaybackState.connecting);
+		this.url = url;
+		if (extractor != null) {
+			extractor.release();
+		}
+		new Thread(() -> {
+			try {
+				blockingInitExtractorAndCodec();
+
+				sonic = new Sonic(sampleRate, channelCount);
+				sonic.setVolume(volume);
+				sonic.setSpeed(speed);
+
+				bgTransition(PlaybackState.stopped);
+				handler.post(() -> result.success(duration));
+			} catch (Exception e) {
+				e.printStackTrace();
+				handler.post(() -> result.error("Error: " + e, null, null));
+			}
+		}).start();
 	}
 
 	public void play(final Integer untilPosition) {
-		// TODO: dynamically adjust the lag.
-		final int lag = 6;
-		final int start = getCurrentPosition();
 		if (untilPosition != null && untilPosition <= start) {
-			return;
+			throw new IllegalArgumentException("untilPosition must be >= 0");
 		}
-		player.start();
+		this.untilPosition = untilPosition;
-		setPlaybackState(PlaybackState.playing);
+		switch (state) {
-		if (endDetector != null) {
+		case stopped:
-			handler.removeCallbacks(endDetector);
+			ensureStopped();
+			transition(PlaybackState.playing);
+			playThread = new PlayThread();
+			playThread.start();
+			break;
+		case paused:
+			synchronized (monitor) {
+				transition(PlaybackState.playing);
+				monitor.notifyAll();
 			}
-		if (untilPosition != null) {
+			break;
-			final int duration = Math.max(0, untilPosition - start - lag);
+		default:
-			handler.postDelayed(new Runnable() {
+			throw new IllegalStateException("Can call play only from stopped and paused states (" + state + ")");
-				@Override
-				public void run() {
-					final int position = getCurrentPosition();
-					if (position > untilPosition - 20) {
-						pause();
-					} else {
-						final int duration = Math.max(0, untilPosition - position - lag);
-						handler.postDelayed(this, duration);
 		}
 	}
-			}, duration);
+
+	private void ensureStopped() {
+		synchronized (monitor) {
+			try {
+				while (playThread != null) {
+					monitor.wait();
+				}
+			} catch (Exception e) {}
 		}
 	}
 
 	public void pause() {
-		player.pause();
+		switch (state) {
-		setPlaybackState(PlaybackState.paused);
+		case playing:
+		case buffering:
+			synchronized (monitor) {
+				transition(PlaybackState.paused);
+				audioTrack.pause();
+				monitor.notifyAll();
+			}
+			break;
+		default:
+			throw new IllegalStateException("Can call pause only from playing and buffering states");
+		}
 	}
 
-	public void stop() {
+	public void stop(final Result result) {
-		player.pause();
+		switch (state) {
-		player.seekTo(0);
+		case stopped:
-		setPlaybackState(PlaybackState.stopped);
+			break;
+		// TODO: Allow stopping from buffered state.
+		case playing:
+		case paused:
+			synchronized (monitor) {
+				// It takes some time for the PlayThread to actually wind down
+				// so other methods that transition from the stopped state should
+				// wait for playThread == null with ensureStopped().
+				PlaybackState oldState = state;
+				transition(PlaybackState.stopped);
+				if (oldState == PlaybackState.paused) {
+					monitor.notifyAll();
+				} else {
+					audioTrack.pause();
+				}
+				new Thread(() -> {
+					ensureStopped();
+					handler.post(() -> result.success(null));
+				}).start();
+			}
+			break;
+		default:
+			throw new IllegalStateException("Can call stop only from playing, paused and buffering states");
+		}
 	}
 
-	public void setVolume(final double volume) {
+	public void setVolume(final float volume) {
-		player.setVolume((float)volume, (float)volume);
+		this.volume = volume;
+		if (sonic != null) {
+			sonic.setVolume(volume);
+		}
 	}
 
+	public void setSpeed(final float speed) {
+		// NOTE: existing audio data in the pipeline will continue
+		// to play out at the speed it was already processed at. So
+		// for a brief moment, checkForDiscontinuity() may erroneously
+		// detect some buffering.
+		// TODO: Sort this out. The cheap workaround would be to disable
+		// checks for discontinuity during this brief moment.
+		this.speed = speed;
+		if (sonic != null) {
+			sonic.setSpeed(speed);
+		}
+		broadcastPlayerState();
+	}
+
+	// TODO: Test whether this times out the MediaCodec on Ogg files.
+	// See: https://stackoverflow.com/questions/22109050/mediacodec-dequeueoutputbuffer-times-out-when-seeking-with-ogg-audio-files
 	public void seek(final int position, final Result result) {
-		stateBeforeSeek = state;
+		synchronized (monitor) {
-		seekPos = position;
+			if (state == PlaybackState.none || state == PlaybackState.connecting) {
-		handler.removeCallbacks(positionObserver);
+				throw new IllegalStateException("Cannot call seek in none or connecting states");
-		setPlaybackState(PlaybackState.buffering);
+			}
-		player.setOnSeekCompleteListener(new MediaPlayer.OnSeekCompleteListener() {
+			if (state == PlaybackState.stopped) {
-			@Override
+				ensureStopped();
-			public void onSeekComplete(final MediaPlayer mp) {
+			}
-				seekPos = null;
+			start = position;
-				setPlaybackState(stateBeforeSeek);
+			if (seekRequests.size() == 0) {
-				stateBeforeSeek = null;
+				stateBeforeSeek = state;
-				result.success(null);
+			}
-				player.setOnSeekCompleteListener(null);
+			seekRequests.addLast(new SeekRequest(position, result));
+			handler.removeCallbacks(positionObserver);
+			transition(PlaybackState.buffering);
+			if (stateBeforeSeek == PlaybackState.stopped) {
+				new Thread(() -> {
+					processSeekRequests();
+				}).start();
+			} else {
+				monitor.notifyAll();
+			}
 		}
-		});
-		player.seekTo(position);
 	}
 
 	public void dispose() {
-		player.release();
+		if (state != PlaybackState.stopped && state != PlaybackState.none) {
-		setPlaybackState(PlaybackState.none);
+			throw new IllegalStateException("Can call dispose only from stopped and none states");
+		}
+		if (extractor != null) {
+			ensureStopped();
+			transition(PlaybackState.none);
+			extractor.release();
+			extractor = null;
+			codec.stop();
+			codec.release();
+			codec = null;
+		}
+	}
+
+	private void blockingInitExtractorAndCodec() throws IOException {
+		extractor = new MediaExtractor();
+		extractor.setDataSource(url);
+		format = selectAudioTrack(extractor);
+		channelCount = format.getInteger(MediaFormat.KEY_CHANNEL_COUNT);
+		sampleRate = format.getInteger(MediaFormat.KEY_SAMPLE_RATE);
+		long durationMs = format.getLong(MediaFormat.KEY_DURATION);
+		duration = (int)(durationMs / 1000);
+		start = 0;
+		codec = MediaCodec.createDecoderByType(format.getString(MediaFormat.KEY_MIME));
+		codec.configure(format, null, null, 0);
+		codec.start();
+	}
+
+	private MediaFormat selectAudioTrack(MediaExtractor extractor) throws IOException {
+		int trackCount = extractor.getTrackCount();
+		for (int i = 0; i < trackCount; i++) {
+			MediaFormat format = extractor.getTrackFormat(i);
+			if (format.getString(MediaFormat.KEY_MIME).startsWith("audio/")) {
+				extractor.selectTrack(i);
+				return format;
+			}
+		}
+		throw new RuntimeException("No audio track found");
+	}
+
+	private void processSeekRequests() {
+		while (seekRequests.size() > 0) {
+			SeekRequest seekRequest = seekRequests.removeFirst();
+			extractor.seekTo(seekRequest.pos*1000L, MediaExtractor.SEEK_TO_CLOSEST_SYNC);
+			if (seekRequests.size() == 0) {
+				bgTransition(stateBeforeSeek);
+				stateBeforeSeek = null;
+			}
+			handler.post(() -> seekRequest.result.success(null));
+		}
 	}
 
 	private void startObservingPosition() {
@@ -248,6 +407,217 @@ public class AudioPlayer implements MethodCallHandler, MediaPlayer.OnCompletionL
 		handler.post(positionObserver);
 	}
 
+	private class PlayThread extends Thread {
+		private static final int TIMEOUT = 1000;
+		private static final int FRAME_SIZE = 1024*2;
+		private static final int BEHIND_LIMIT = 500; // ms
+		private byte[] silence;
+		private boolean finishedDecoding = false;
+
+		@Override
+		public void run() {
+
+			int encoding = AudioFormat.ENCODING_PCM_16BIT;
+			int channelFormat = channelCount==1?AudioFormat.CHANNEL_OUT_MONO:AudioFormat.CHANNEL_OUT_STEREO;
+			int minSize = AudioTrack.getMinBufferSize(sampleRate, channelFormat, encoding);
+			int audioTrackBufferSize = minSize * 4;
+			audioTrack = new AudioTrack(
+					AudioManager.STREAM_MUSIC,
+					sampleRate,
+					channelFormat,
+					encoding,
+					audioTrackBufferSize,
+					AudioTrack.MODE_STREAM);
+
+			silence = new byte[audioTrackBufferSize];
+
+			MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();
+			boolean firstSample = true;
+			int decoderIdleCount = 0;
+			boolean finishedReading = false;
+			int progress = 0;
+			// The extractor position seems to jump around at the beginning.
+			// This is a hack to address that.
+			long behindStartTime = 0;
+			byte[] sonicOut = new byte[audioTrackBufferSize];
+			try {
+				audioTrack.play();
+				while (!finishedDecoding) {
+
+					if (checkForRequest()) continue;
+
+					// put data into input buffer
+
+					if (!finishedReading) {
+						int inputBufferIndex = codec.dequeueInputBuffer(TIMEOUT);
+						if (inputBufferIndex >= 0) {
+							ByteBuffer inputBuffer = codec.getInputBuffer(inputBufferIndex);
+							long presentationTime = extractor.getSampleTime();
+							int presentationTimeMs = (int)(presentationTime / 1000);
+							if (presentationTimeMs < start) {
+								if (behindStartTime == 0) behindStartTime = System.currentTimeMillis();
+								if (System.currentTimeMillis() - behindStartTime > BEHIND_LIMIT) {
+									System.out.println("Too early, re-seeking");
+									extractor.seekTo(start*1000L, MediaExtractor.SEEK_TO_CLOSEST_SYNC);
+									behindStartTime = 0;
+								}
+							} else {
+								behindStartTime = 0;
+							}
+							int sampleSize = extractor.readSampleData(inputBuffer, 0);
+							if (firstSample && sampleSize == 2 && format.getString(MediaFormat.KEY_MIME).equals("audio/mp4a-latm")) {
+								// Skip initial frames.
+								extractor.advance();
+							} else if (sampleSize >= 0) {
+								codec.queueInputBuffer(inputBufferIndex, 0, sampleSize, presentationTime, 0);
+								extractor.advance();
+							} else {
+								codec.queueInputBuffer(inputBufferIndex, 0, 0, -1, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
+								finishedReading = true;
+							}
+							firstSample = false;
+						}
+					}
+
+					if (checkForRequest()) continue;
+
+					// read data from output buffer
+
+					int outputBufferIndex = codec.dequeueOutputBuffer(info, TIMEOUT);
+					decoderIdleCount++;
+					if (outputBufferIndex >= 0) {
+						int currentPosition = (int)(info.presentationTimeUs/1000);
+						ByteBuffer buf = codec.getOutputBuffer(outputBufferIndex);
+						if (info.size > 0) {
+							decoderIdleCount = 0;
+
+							final byte[] chunk = new byte[info.size];
+							buf.get(chunk);
+							buf.clear();
+
+							// put decoded data into sonic
+
+							if (chunk.length > 0) {
+								sonic.writeBytesToStream(chunk, chunk.length);
+							} else {
+								sonic.flushStream();
+							}
+
+							// output sonic'd data to audioTrack
+
+							int numWritten;
+							do {
+								numWritten = sonic.readBytesFromStream(sonicOut, sonicOut.length);
+								if (numWritten > 0) {
+									audioTrack.write(sonicOut, 0, numWritten);
+								}
+							} while (numWritten > 0);
+						}
+
+						// Detect end of playback
+
+						codec.releaseOutputBuffer(outputBufferIndex, false);
+						if ((info.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
+							if (untilPosition != null) {
+								extractor.release();
+								codec.flush();
+								codec.stop();
+								codec.release();
+								blockingInitExtractorAndCodec();
+								finishedReading = false;
+								finishedDecoding = false;
+								decoderIdleCount = 0;
+								audioTrack.pause();
+								bgTransition(PlaybackState.paused);
+							} else {
+								audioTrack.pause();
+								finishedDecoding = true;
+							}
+						} else if (untilPosition != null && currentPosition >= untilPosition) {
+							// NOTE: When streaming audio over bluetooth, it clips off
+							// the last 200-300ms of the clip, even though it has been
+							// written to the AudioTrack. So, we need an option to pad the
+							// audio with an extra 200-300ms of silence.
+							// Could be a good idea to do the same at the start
+							// since some bluetooth headphones fade in and miss the
+							// first little bit.
+
+							Arrays.fill(sonicOut, (byte)0);
+							audioTrack.write(sonicOut, 0, sonicOut.length);
+							bgTransition(PlaybackState.paused);
+							audioTrack.pause();
+						}
+					} else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
+						// Don't expect this to happen in audio files, but could be wrong.
+						// TODO: Investigate.
+						//MediaFormat newFormat = codec.getOutputFormat();
+					}
+					if (decoderIdleCount >= 100) {
+						// Data has stopped coming through the pipeline despite not receiving a
+						// BUFFER_FLAG_END_OF_STREAM signal, so stop.
+						System.out.println("decoderIdleCount >= 100. finishedDecoding = true");
+						finishedDecoding = true;
+						audioTrack.pause();
+					}
+				}
+			} catch (IOException e) {
+				e.printStackTrace();
+			} finally {
+				codec.flush();
+				audioTrack.flush();
+				audioTrack.release();
+				audioTrack = null;
+				synchronized (monitor) {
+					start = 0;
+					untilPosition = null;
+					bgTransition(PlaybackState.stopped);
+					extractor.seekTo(0L, MediaExtractor.SEEK_TO_CLOSEST_SYNC);
+					playThread = null;
+					monitor.notifyAll();
+				}
+			}
+		}
+
+		// Return true to "continue" to the audio loop
+		private boolean checkForRequest() {
+			try {
+				synchronized (monitor) {
+					if (state == PlaybackState.paused) {
+						while (state == PlaybackState.paused) {
+							monitor.wait();
+						}
+						// Unpaused
+						// Reset updateTime for higher accuracy.
+						bgTransition(state);
+						if (state == PlaybackState.playing) {
+							audioTrack.play();
+						} else if (state == PlaybackState.buffering) {
+							// TODO: What if we are in the second checkForRequest call and
+							// we ask to continue the loop, we may forget about dequeued
+							// input buffers. Need to handle this correctly.
+							return true;
+						}
+					} else if (state == PlaybackState.buffering && seekRequests.size() > 0) {
+						// Seek requested
+						codec.flush();
+						audioTrack.flush();
+						processSeekRequests();
+						if (state != PlaybackState.stopped) {
+							// The == stopped case is handled below.
+							return true;
+						}
+					}
+					if (state == PlaybackState.stopped) {
+						finishedDecoding = true;
+						return true;
+					}
+				}
+			}
+			catch (Exception e) {}
+			return false;
+		}
+	}
+
 	enum PlaybackState {
 		none,
 		stopped,
@@ -256,4 +626,14 @@ public class AudioPlayer implements MethodCallHandler, MediaPlayer.OnCompletionL
 		buffering,
 		connecting
 	}
+
+	class SeekRequest {
+		public final int pos;
+		public final Result result;
+
+		public SeekRequest(int pos, Result result) {
+			this.pos = pos;
+			this.result = result;
+		}
+	}
 }

android/src/main/java/com/ryanheise/just_audio/JustAudioPlugin.java

@@ -5,6 +5,7 @@ import io.flutter.plugin.common.MethodChannel;
 import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
 import io.flutter.plugin.common.MethodChannel.Result;
 import io.flutter.plugin.common.PluginRegistry.Registrar;
+import java.util.List;
 
 /** JustAudioPlugin */
 public class JustAudioPlugin implements MethodCallHandler {
@@ -24,7 +25,8 @@ public class JustAudioPlugin implements MethodCallHandler {
   public void onMethodCall(MethodCall call, Result result) {
 		switch (call.method) {
 		case "init":
-			String id = (String)call.arguments;
+			final List<?> args = (List<?>)call.arguments;
+			String id = (String)args.get(0);
 			new AudioPlayer(registrar, id);
 			result.success(null);
 			break;

example/.gitignore

@@ -24,6 +24,7 @@
 **/doc/api/
 .dart_tool/
 .flutter-plugins
+.flutter-plugins-dependencies
 .packages
 .pub-cache/
 .pub/

example/android/app/build.gradle

@@ -34,11 +34,11 @@ android {
     defaultConfig {
         // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId "com.ryanheise.just_audio_example"
-        minSdkVersion 16
+        minSdkVersion 21
         targetSdkVersion 28
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
-        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
 
     buildTypes {
@@ -56,6 +56,6 @@ flutter {
 
 dependencies {
     testImplementation 'junit:junit:4.12'
-    androidTestImplementation 'com.android.support.test:runner:1.0.2'
+    androidTestImplementation 'androidx.test:runner:1.1.1'
-    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
+    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
 }

example/android/build.gradle

@@ -5,7 +5,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.2.1'
+        classpath 'com.android.tools.build:gradle:3.5.0'
     }
 }
 

example/android/gradle.properties

@@ -1,2 +1,4 @@
 org.gradle.jvmargs=-Xmx1536M
-
+android.enableR8=true
+android.useAndroidX=true
+android.enableJetifier=true

example/android/gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.10.2-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.4.1-all.zip

example/lib/main.dart

@@ -1,10 +1,7 @@
-import 'dart:math';
-
 import 'package:flutter/material.dart';
-import 'dart:async';
 
-import 'package:flutter/services.dart';
 import 'package:just_audio/just_audio.dart';
+import 'package:rxdart/rxdart.dart';
 
 void main() => runApp(MyApp());
 
@@ -14,11 +11,14 @@ class MyApp extends StatefulWidget {
 }
 
 class _MyAppState extends State<MyApp> {
-  final AudioPlayer _player = AudioPlayer();
+  final _volumeSubject = BehaviorSubject.seeded(1.0);
+  final _speedSubject = BehaviorSubject.seeded(1.0);
+  AudioPlayer _player;
 
   @override
   void initState() {
     super.initState();
+    _player = AudioPlayer();
     _player.setUrl(
         "https://s3.amazonaws.com/scifri-episodes/scifri20181123-episode.mp3");
   }
@@ -82,6 +82,7 @@ class _MyAppState extends State<MyApp> {
                   );
                 },
               ),
+              Text("Track position"),
               StreamBuilder<Duration>(
                 stream: _player.durationStream,
                 builder: (context, snapshot) {
@@ -101,6 +102,34 @@ class _MyAppState extends State<MyApp> {
                   );
                 },
               ),
+              Text("Volume"),
+              StreamBuilder<double>(
+                stream: _volumeSubject.stream,
+                builder: (context, snapshot) => Slider(
+                  divisions: 20,
+                  min: 0.0,
+                  max: 2.0,
+                  value: snapshot.data ?? 1.0,
+                  onChanged: (value) {
+                    _volumeSubject.add(value);
+                    _player.setVolume(value);
+                  },
+                ),
+              ),
+              Text("Speed"),
+              StreamBuilder<double>(
+                stream: _speedSubject.stream,
+                builder: (context, snapshot) => Slider(
+                  divisions: 10,
+                  min: 0.5,
+                  max: 1.5,
+                  value: snapshot.data ?? 1.0,
+                  onChanged: (value) {
+                    _speedSubject.add(value);
+                    _player.setSpeed(value);
+                  },
+                ),
+              ),
             ],
           ),
         ),

example/pubspec.lock

@@ -7,7 +7,7 @@ packages:
       name: archive
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.10"
+    version: "2.0.11"
   args:
     dependency: transitive
     description:
@@ -21,7 +21,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.3.0"
+    version: "2.4.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -87,21 +87,21 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "0.0.1"
+    version: "0.0.2"
   matcher:
     dependency: transitive
     description:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.5"
+    version: "0.12.6"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.7"
+    version: "1.1.8"
   path:
     dependency: transitive
     description:
@@ -145,12 +145,12 @@ packages:
     source: hosted
     version: "2.0.5"
   rxdart:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: rxdart
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.22.6"
+    version: "0.23.1"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -197,7 +197,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.5"
+    version: "0.2.11"
   typed_data:
     dependency: transitive
     description:
@@ -220,5 +220,5 @@ packages:
     source: hosted
     version: "3.5.0"
 sdks:
-  dart: ">=2.4.0 <3.0.0"
+  dart: ">=2.6.0 <3.0.0"
   flutter: ">=1.9.1+hotfix.5 <2.0.0"

example/pubspec.yaml

@@ -6,9 +6,8 @@ dependencies:
   flutter:
     sdk: flutter
 
-  # The following adds the Cupertino Icons font to your application.
-  # Use with the CupertinoIcons class for iOS style icons.
   cupertino_icons: ^0.1.2
+  rxdart: ^0.23.1
 
 dev_dependencies:
   flutter_test:

ios/Classes/AudioPlayer.m

@@ -60,6 +60,9 @@
 	} else if ([@"setVolume" isEqualToString:call.method]) {
 		[self setVolume:(float)[args[0] doubleValue]];
 		result(nil);
+	} else if ([@"setSpeed" isEqualToString:call.method]) {
+		[self setSpeed:(float)[args[0] doubleValue]];
+		result(nil);
 	} else if ([@"seek" isEqualToString:call.method]) {
 		[self seek:[args[0] intValue] result:result];
 		result(nil);
@@ -92,7 +95,7 @@
 	long long now = (long long)([[NSDate date] timeIntervalSince1970] * 1000.0);
 	int position = [self getCurrentPosition];
 	long long timeSinceLastUpdate = now - _updateTime;
-	long long expectedPosition = _updatePosition + timeSinceLastUpdate;
+	long long expectedPosition = _updatePosition + timeSinceLastUpdate; // TODO: * speed
 	long long drift = position - expectedPosition;
 	// Update if we've drifted or just started observing
 	if (_updateTime == 0L) {
@@ -257,6 +260,14 @@
 	[_player setVolume:volume];
 }
 
+- (void)setSpeed:(float)speed {
+	//if (speed == 1.0
+	//		|| speed < 1.0 && _player.currentItem.canPlaySlowForward
+	//		|| speed > 1.0 && _player.currentItem.canPlayFastForward) {
+	//	_player.rate = speed;
+	//}
+}
+
 - (void)seek:(int)position result:(FlutterResult)result {
 	_stateBeforeSeek = _state;
 	_seekPos = position;

ios/Classes/JustAudioPlugin.m

@@ -23,7 +23,8 @@
 
 - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
 	if ([@"init" isEqualToString:call.method]) {
-    NSString* playerId = call.arguments;
+		NSArray* args = (NSArray*)call.arguments;
+		NSString* playerId = args[0];
 		AudioPlayer* player = [[AudioPlayer alloc] initWithRegistrar:_registrar playerId:playerId];
 		result(nil);
 	} else {

lib/just_audio.dart

@@ -46,8 +46,8 @@ import 'package:rxdart/rxdart.dart';
 class AudioPlayer {
   static final _mainChannel = MethodChannel('com.ryanheise.just_audio.methods');
 
-  static Future<MethodChannel> _createChannel(int id) async {
+  static Future<MethodChannel> _init(int id) async {
-    await _mainChannel.invokeMethod('init', '$id');
+    await _mainChannel.invokeMethod('init', ['$id']);
     return MethodChannel('com.ryanheise.just_audio.methods.$id');
   }
 
@@ -69,22 +69,31 @@ class AudioPlayer {
 
   final _playbackStateSubject = BehaviorSubject<AudioPlaybackState>();
 
+  double _volume = 1.0;
+
+  double _speed = 1.0;
+
   /// Creates an [AudioPlayer].
   factory AudioPlayer() =>
       AudioPlayer._internal(DateTime.now().microsecondsSinceEpoch);
 
-  AudioPlayer._internal(this._id) : _channel = _createChannel(_id) {
+  AudioPlayer._internal(this._id) : _channel = _init(_id) {
     _eventChannelStream = EventChannel('com.ryanheise.just_audio.events.$_id')
         .receiveBroadcastStream()
         .map((data) => _audioPlayerState = AudioPlayerState(
               state: AudioPlaybackState.values[data[0]],
               updatePosition: Duration(milliseconds: data[1]),
               updateTime: Duration(milliseconds: data[2]),
+              speed: _speed,
             ));
     _eventChannelStreamSubscription =
         _eventChannelStream.listen(_playerStateSubject.add);
     _playbackStateSubject
         .addStream(playerStateStream.map((state) => state.state).distinct());
+
+    playerStateStream.listen((state) {
+      print("state: $state");
+    });
   }
 
   /// The duration of any media set via [setUrl], [setFilePath] or [setAsset],
@@ -107,11 +116,18 @@ class AudioPlayer {
   /// A stream periodically tracking the current position of this player.
   Stream<Duration> getPositionStream(
           [final Duration period = const Duration(milliseconds: 200)]) =>
-      Observable.combineLatest2<AudioPlayerState, void, Duration>(
+      Rx.combineLatest2<AudioPlayerState, void, Duration>(
           playerStateStream,
-          Observable.periodic(period),
+          // TODO: emit periodically only in playing state.
+          Stream.periodic(period),
           (state, _) => state.position);
 
+  /// The current volume of the player.
+  double get volume => _volume;
+
+  /// The current speed of the player.
+  double get speed => _speed;
+
   /// Loads audio media from a URL and returns the duration of that audio.
   Future<Duration> setUrl(final String url) async {
     _durationFuture =
@@ -170,10 +186,11 @@ class AudioPlayer {
   }
 
   /// Stops the currently playing media such that the next [play] invocation
-  /// will start from position 0. It is legal to invoke this method from any
+  /// will start from position 0. It is legal to invoke this method only from
-  /// state except for:
+  /// the following states:
   ///
-  /// * [AudioPlaybackState.none]
+  /// * [AudioPlaybackState.playing]
+  /// * [AudioPlaybackState.paused]
   /// * [AudioPlaybackState.stopped]
   Future<void> stop() async {
     await _invokeMethod('stop');
@@ -181,9 +198,16 @@ class AudioPlayer {
 
   /// Sets the volume of this player, where 1.0 is normal volume.
   Future<void> setVolume(final double volume) async {
+    _volume = volume;
     await _invokeMethod('setVolume', [volume]);
   }
 
+  /// Sets the playback speed of this player, where 1.0 is normal speed.
+  Future<void> setSpeed(final double speed) async {
+    _speed = speed;
+    await _invokeMethod('setSpeed', [speed]);
+  }
+
   /// Seeks to a particular position. It is legal to invoke this method
   /// from any state except for [AudioPlaybackState.none].
   Future<void> seek(final Duration position) async {
@@ -218,18 +242,26 @@ class AudioPlayerState {
   /// The position at [updateTime].
   final Duration updatePosition;
 
+  /// The playback speed.
+  final double speed;
+
   AudioPlayerState({
     @required this.state,
     @required this.updateTime,
     @required this.updatePosition,
+    @required this.speed,
   });
 
   /// The current position of the player.
   Duration get position => state == AudioPlaybackState.playing
       ? updatePosition +
           (Duration(milliseconds: DateTime.now().millisecondsSinceEpoch) -
-              updateTime)
+                  updateTime) *
+              speed
       : updatePosition;
+
+  @override
+  String toString() => "{state=$state, updateTime=$updateTime, updatePosition=$updatePosition, speed=$speed}";
 }
 
 /// Enumerates the different playback states of a player.

pubspec.lock

@@ -1,13 +1,27 @@
 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
+  archive:
+    dependency: transitive
+    description:
+      name: archive
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.11"
+  args:
+    dependency: transitive
+    description:
+      name: args
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.5.2"
   async:
     dependency: transitive
     description:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.3.0"
+    version: "2.4.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -29,6 +43,20 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.14.11"
+  convert:
+    dependency: transitive
+    description:
+      name: convert
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.1"
+  crypto:
+    dependency: transitive
+    description:
+      name: crypto
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.3"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -39,20 +67,27 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  image:
+    dependency: transitive
+    description:
+      name: image
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.4"
   matcher:
     dependency: transitive
     description:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.5"
+    version: "0.12.6"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.7"
+    version: "1.1.8"
   path:
     dependency: "direct main"
     description:
@@ -74,6 +109,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.8.0+1"
+  petitparser:
+    dependency: transitive
+    description:
+      name: petitparser
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.4.0"
   platform:
     dependency: transitive
     description:
@@ -94,7 +136,7 @@ packages:
       name: rxdart
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.22.6"
+    version: "0.23.1"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -141,7 +183,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.5"
+    version: "0.2.11"
   typed_data:
     dependency: transitive
     description:
@@ -156,6 +198,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.8"
+  xml:
+    dependency: transitive
+    description:
+      name: xml
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "3.5.0"
 sdks:
-  dart: ">=2.2.2 <3.0.0"
+  dart: ">=2.6.0 <3.0.0"
   flutter: ">=1.9.1+hotfix.5 <2.0.0"

pubspec.yaml

@@ -8,7 +8,7 @@ environment:
   sdk: ">=2.1.0 <3.0.0"
 
 dependencies:
-  rxdart: ^0.22.6
+  rxdart: ^0.23.1
   path: ^1.6.4
   path_provider: ^1.4.5
   flutter: