Start cleaning up buffering.

- Always continue loading if we've got less than the minimum
  amount of media in the buffer.
- Use LoadControl in ExtractorSampleSource.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=125679669

library/src/main/java/com/google/android/exoplayer/DefaultLoadControl.java

@@ -58,8 +58,6 @@ public final class DefaultLoadControl implements LoadControl {
 
   public static final int DEFAULT_LOW_WATERMARK_MS = 15000;
   public static final int DEFAULT_HIGH_WATERMARK_MS = 30000;
-  public static final float DEFAULT_LOW_BUFFER_LOAD = 0.2f;
-  public static final float DEFAULT_HIGH_BUFFER_LOAD = 0.8f;
 
   private static final int ABOVE_HIGH_WATERMARK = 0;
   private static final int BETWEEN_WATERMARKS = 1;
@@ -73,12 +71,10 @@ public final class DefaultLoadControl implements LoadControl {
 
   private final long lowWatermarkUs;
   private final long highWatermarkUs;
-  private final float lowBufferLoad;
-  private final float highBufferLoad;
 
-  private int targetBufferSize;
   private long maxLoadStartPositionUs;
-  private int bufferState;
+  private int targetBufferSize;
+  private boolean targetBufferSizeReached;
   private boolean fillingBuffers;
   private boolean streamingPrioritySet;
 
@@ -102,7 +98,7 @@ public final class DefaultLoadControl implements LoadControl {
   public DefaultLoadControl(DefaultAllocator allocator, Handler eventHandler,
       EventListener eventListener) {
     this(allocator, eventHandler, eventListener, DEFAULT_LOW_WATERMARK_MS,
-        DEFAULT_HIGH_WATERMARK_MS, DEFAULT_LOW_BUFFER_LOAD, DEFAULT_HIGH_BUFFER_LOAD);
+        DEFAULT_HIGH_WATERMARK_MS);
   }
 
   /**
@@ -117,15 +113,9 @@ public final class DefaultLoadControl implements LoadControl {
    *     the filling state.
    * @param highWatermarkMs The minimum duration of media that can be buffered for the control to
    *     transition from filling to draining.
-   * @param lowBufferLoad The minimum fraction of the buffer that must be utilized for the control
-   *     to be in the draining state. If the utilization is lower, then the control will transition
-   *     to the filling state.
-   * @param highBufferLoad The minimum fraction of the buffer that must be utilized for the control
-   *     to transition from the loading state to the draining state.
    */
   public DefaultLoadControl(DefaultAllocator allocator, Handler eventHandler,
-      EventListener eventListener, int lowWatermarkMs, int highWatermarkMs, float lowBufferLoad,
+      EventListener eventListener, int lowWatermarkMs, int highWatermarkMs) {
-      float highBufferLoad) {
     this.allocator = allocator;
     this.eventHandler = eventHandler;
     this.eventListener = eventListener;
@@ -133,8 +123,6 @@ public final class DefaultLoadControl implements LoadControl {
     this.loaderStates = new HashMap<>();
     this.lowWatermarkUs = lowWatermarkMs * 1000L;
     this.highWatermarkUs = highWatermarkMs * 1000L;
-    this.lowBufferLoad = lowBufferLoad;
-    this.highBufferLoad = highBufferLoad;
   }
 
   @Override
@@ -151,6 +139,7 @@ public final class DefaultLoadControl implements LoadControl {
     LoaderState state = loaderStates.remove(loader);
     targetBufferSize -= state.bufferSizeContribution;
     allocator.setTargetBufferSize(targetBufferSize);
+    targetBufferSizeReached = allocator.getTotalBytesAllocated() >= targetBufferSize;
     updateControlState();
   }
 
@@ -174,11 +163,10 @@ public final class DefaultLoadControl implements LoadControl {
     }
 
     // Update the buffer state.
-    int currentBufferSize = allocator.getTotalBytesAllocated();
+    boolean targetBufferSizeReached = allocator.getTotalBytesAllocated() >= targetBufferSize;
-    int bufferState = getBufferState(currentBufferSize);
+    boolean bufferStateChanged = this.targetBufferSizeReached != targetBufferSizeReached;
-    boolean bufferStateChanged = this.bufferState != bufferState;
     if (bufferStateChanged) {
-      this.bufferState = bufferState;
+      this.targetBufferSizeReached = targetBufferSizeReached;
     }
 
     // If either of the individual states have changed, update the shared control state.
@@ -186,8 +174,7 @@ public final class DefaultLoadControl implements LoadControl {
       updateControlState();
     }
 
-    return currentBufferSize < targetBufferSize && nextLoadPositionUs != C.UNSET_TIME_US
+    return nextLoadPositionUs != C.UNSET_TIME_US && nextLoadPositionUs <= maxLoadStartPositionUs;
-        && nextLoadPositionUs <= maxLoadStartPositionUs;
   }
 
   private int getLoaderBufferState(long playbackPositionUs, long nextLoadPositionUs) {
@@ -201,27 +188,20 @@ public final class DefaultLoadControl implements LoadControl {
     }
   }
 
-  private int getBufferState(int currentBufferSize) {
-    float bufferLoad = (float) currentBufferSize / targetBufferSize;
-    return bufferLoad > highBufferLoad ? ABOVE_HIGH_WATERMARK
-        : bufferLoad < lowBufferLoad ? BELOW_LOW_WATERMARK
-        : BETWEEN_WATERMARKS;
-  }
-
   private void updateControlState() {
     boolean loading = false;
     boolean haveNextLoadPosition = false;
-    int highestState = bufferState;
+    int worstLoaderState = ABOVE_HIGH_WATERMARK;
     for (int i = 0; i < loaders.size(); i++) {
       LoaderState loaderState = loaderStates.get(loaders.get(i));
       loading |= loaderState.loading;
       haveNextLoadPosition |= loaderState.nextLoadPositionUs != C.UNSET_TIME_US;
-      highestState = Math.max(highestState, loaderState.bufferState);
+      worstLoaderState = Math.max(worstLoaderState, loaderState.bufferState);
     }
 
     fillingBuffers = !loaders.isEmpty() && (loading || haveNextLoadPosition)
-        && (highestState == BELOW_LOW_WATERMARK
+        && (worstLoaderState == BELOW_LOW_WATERMARK
-        || (highestState == BETWEEN_WATERMARKS && fillingBuffers));
+        || (worstLoaderState == BETWEEN_WATERMARKS && fillingBuffers && !targetBufferSizeReached));
     if (fillingBuffers && !streamingPrioritySet) {
       NetworkLock.instance.add(NetworkLock.STREAMING_PRIORITY);
       streamingPrioritySet = true;

library/src/main/java/com/google/android/exoplayer/extractor/ExtractorSampleSource.java

@@ -17,14 +17,15 @@ package com.google.android.exoplayer.extractor;
 
 import com.google.android.exoplayer.C;
 import com.google.android.exoplayer.DecoderInputBuffer;
+import com.google.android.exoplayer.DefaultLoadControl;
 import com.google.android.exoplayer.FormatHolder;
+import com.google.android.exoplayer.LoadControl;
 import com.google.android.exoplayer.ParserException;
 import com.google.android.exoplayer.SampleSource;
 import com.google.android.exoplayer.TrackGroup;
 import com.google.android.exoplayer.TrackGroupArray;
 import com.google.android.exoplayer.TrackSelection;
 import com.google.android.exoplayer.TrackStream;
-import com.google.android.exoplayer.upstream.Allocator;
 import com.google.android.exoplayer.upstream.BandwidthMeter;
 import com.google.android.exoplayer.upstream.DataSource;
 import com.google.android.exoplayer.upstream.DataSourceFactory;
@@ -36,6 +37,7 @@ import com.google.android.exoplayer.util.Assertions;
 import com.google.android.exoplayer.util.Util;
 
 import android.net.Uri;
+import android.os.ConditionVariable;
 import android.os.Handler;
 
 import java.io.EOFException;
@@ -125,7 +127,8 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
   private final Handler eventHandler;
   private final EventListener eventListener;
   private final DataSource dataSource;
-  private final Allocator allocator;
+  private final ConditionVariable loadCondition;
+  private final LoadControl loadControl;
   private final Loader loader;
   private final ExtractorHolder extractorHolder;
 
@@ -186,7 +189,8 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
     this.eventListener = eventListener;
     this.eventHandler = eventHandler;
     dataSource = dataSourceFactory.createDataSource(bandwidthMeter);
-    allocator = new DefaultAllocator(C.DEFAULT_BUFFER_SEGMENT_SIZE);
+    loadCondition = new ConditionVariable();
+    loadControl = new DefaultLoadControl(new DefaultAllocator(C.DEFAULT_BUFFER_SEGMENT_SIZE));
     loader = new Loader("Loader:ExtractorSampleSource");
     extractorHolder = new ExtractorHolder(extractors, this);
     pendingResetPositionUs = C.UNSET_TIME_US;
@@ -308,6 +312,7 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
       return true;
     }
     if (seekMap != null && tracksBuilt && haveFormatsForAllTracks()) {
+      loadCondition.close();
       int trackCount = sampleQueues.length;
       TrackGroup[] trackArray = new TrackGroup[trackCount];
       trackEnabledStates = new boolean[trackCount];
@@ -322,6 +327,7 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
     // We're not prepared.
     maybeThrowError();
     if (!loader.isLoading()) {
+      loadCondition.open();
       startLoading();
     }
     return false;
@@ -341,6 +347,7 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
   public TrackStream[] selectTracks(List<TrackStream> oldStreams,
       List<TrackSelection> newSelections, long positionUs) {
     Assertions.checkState(prepared);
+    boolean tracksWereEnabled = enabledTrackCount > 0;
     // Unselect old tracks.
     for (int i = 0; i < oldStreams.size(); i++) {
       int track = ((TrackStreamImpl) oldStreams.get(i)).track;
@@ -372,19 +379,33 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
     }
     // Cancel or start requests as necessary.
     if (enabledTrackCount == 0) {
+      if (tracksWereEnabled) {
+        loadControl.unregister(this);
+        loadCondition.close();
+      }
       if (loader.isLoading()) {
         loader.cancelLoading();
       }
-    } else if (seenFirstTrackSelection ? newStreams.length > 0 : positionUs != 0) {
+    } else {
+      if (!tracksWereEnabled) {
+        loadControl.register(this, C.DEFAULT_MUXED_BUFFER_SIZE);
+        loadCondition.open();
+      }
+      if (seenFirstTrackSelection ? newStreams.length > 0 : positionUs != 0) {
         seekToUs(positionUs);
       }
+    }
     seenFirstTrackSelection = true;
     return newStreams;
   }
 
   @Override
   public void continueBuffering(long playbackPositionUs) {
-    // Do nothing.
+    if (loadControl.update(this, playbackPositionUs, getBufferedPositionUs(), loader.isLoading())) {
+      loadCondition.open();
+    } else {
+      loadCondition.close();
+    }
   }
 
   @Override
@@ -434,6 +455,9 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
     for (DefaultTrackOutput sampleQueue : sampleQueues) {
       sampleQueue.disable();
     }
+    if (enabledTrackCount > 0) {
+      loadControl.unregister(this);
+    }
     loader.release();
   }
 
@@ -498,7 +522,7 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
   @Override
   public TrackOutput track(int id) {
     sampleQueues = Arrays.copyOf(sampleQueues, sampleQueues.length + 1);
-    DefaultTrackOutput sampleQueue = new DefaultTrackOutput(allocator);
+    DefaultTrackOutput sampleQueue = new DefaultTrackOutput(loadControl.getAllocator());
     sampleQueues[sampleQueues.length - 1] = sampleQueue;
     return sampleQueue;
   }
@@ -536,7 +560,7 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
 
   private void startLoading() {
     ExtractingLoadable loadable = new ExtractingLoadable(uri, dataSource, extractorHolder,
-        allocator, C.DEFAULT_MUXED_BUFFER_SIZE);
+        loadCondition);
     if (prepared) {
       Assertions.checkState(isPendingReset());
       if (durationUs != C.UNSET_TIME_US && pendingResetPositionUs >= durationUs) {
@@ -657,8 +681,7 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
     private final Uri uri;
     private final DataSource dataSource;
     private final ExtractorHolder extractorHolder;
-    private final Allocator allocator;
+    private final ConditionVariable loadCondition;
-    private final int requestedBufferSize;
     private final PositionHolder positionHolder;
 
     private volatile boolean loadCanceled;
@@ -667,12 +690,11 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
     private long length;
 
     public ExtractingLoadable(Uri uri, DataSource dataSource, ExtractorHolder extractorHolder,
-        Allocator allocator, int requestedBufferSize) {
+        ConditionVariable loadCondition) {
       this.uri = Assertions.checkNotNull(uri);
       this.dataSource = Assertions.checkNotNull(dataSource);
       this.extractorHolder = Assertions.checkNotNull(extractorHolder);
-      this.allocator = Assertions.checkNotNull(allocator);
+      this.loadCondition = loadCondition;
-      this.requestedBufferSize = requestedBufferSize;
       this.positionHolder = new PositionHolder();
       this.pendingExtractorSeek = true;
       this.length = C.LENGTH_UNBOUNDED;
@@ -711,11 +733,10 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
             pendingExtractorSeek = false;
           }
           while (result == Extractor.RESULT_CONTINUE && !loadCanceled) {
-            allocator.blockWhileTotalBytesAllocatedExceeds(requestedBufferSize);
+            // TODO: Prevent the loader from loading too much data between evaluations of the
+            // buffering condition.
+            loadCondition.block();
             result = extractor.read(input, positionHolder);
-            // TODO: Implement throttling to stop us from buffering data too often.
-            // TODO: Block buffering between the point at which we have sufficient data for
-            // preparation to complete and the first call to endTrackSelection.
           }
         } finally {
           if (result == Extractor.RESULT_SEEK) {

library/src/main/java/com/google/android/exoplayer/upstream/Allocator.java

@@ -39,19 +39,10 @@ public interface Allocator {
 
   /**
    * Hints to the {@link Allocator} that it should make a best effort to release any memory that it
-   * has allocated that it no longer requires.
+   * has allocated beyond the target buffer size.
    */
   void trim();
 
-  /**
-   * Blocks execution until the number of bytes allocated is not greater than the limit, or the
-   * thread is interrupted.
-   *
-   * @param limit The limit in bytes.
-   * @throws InterruptedException If the thread is interrupted.
-   */
-  void blockWhileTotalBytesAllocatedExceeds(int limit) throws InterruptedException;
-
   /**
    * Returns the total number of bytes currently allocated.
    */

library/src/main/java/com/google/android/exoplayer/upstream/DefaultAllocator.java

@@ -47,7 +47,7 @@ public final class DefaultAllocator implements Allocator {
   /**
    * Constructs a pool with some {@link Allocation}s created up front.
    * <p>
-   * Note: Initial {@link Allocation}s will never be discarded by {@link #trim(int)}.
+   * Note: Initial {@link Allocation}s will never be discarded by {@link #trim()}.
    *
    * @param individualAllocationSize The length of each individual allocation.
    * @param initialAllocationCount The number of allocations to create up front.
@@ -70,7 +70,11 @@ public final class DefaultAllocator implements Allocator {
   }
 
   public synchronized void setTargetBufferSize(int targetBufferSize) {
+    boolean targetBufferSizeReduced = targetBufferSize < this.targetBufferSize;
     this.targetBufferSize = targetBufferSize;
+    if (targetBufferSizeReduced) {
+      trim();
+    }
   }
 
   @Override
@@ -147,14 +151,6 @@ public final class DefaultAllocator implements Allocator {
     return allocatedCount * individualAllocationSize;
   }
 
-  @Override
-  public synchronized void blockWhileTotalBytesAllocatedExceeds(int limit)
-      throws InterruptedException {
-    while (getTotalBytesAllocated() > limit) {
-      wait();
-    }
-  }
-
   @Override
   public int getIndividualAllocationLength() {
     return individualAllocationSize;