Make SampleSource interfaces right for TrackSelector.

The TrackSelector API will look like:

TrackSelection[] selectTrack(
    TrackRenderer[] renderers, TrackGroup[] trackGroups);

In this CL:

- SampleSources return TrackGroup[], so that the result can be easily
  passed to the selector.
- TrackStream gets its own file to sit alongside other Track* classes.
- A TrackSelection object is introduced to encapsulate group and track
  indices.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=115251331

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

@@ -16,7 +16,6 @@
 package com.google.android.exoplayer;
 
 import com.google.android.exoplayer.ExoPlayer.ExoPlayerComponent;
-import com.google.android.exoplayer.SampleSource.TrackStream;
 import com.google.android.exoplayer.util.Assertions;
 import com.google.android.exoplayer.util.PriorityHandlerThread;
 import com.google.android.exoplayer.util.TraceUtil;
@@ -75,8 +74,7 @@ import java.util.concurrent.atomic.AtomicInteger;
   private final long minRebufferUs;
   private final List<TrackRenderer> enabledRenderers;
   private final int[] selectedTrackIndices;
-  private final int[][] groupIndices;
+  private final TrackSelection[][] trackSelections;
-  private final int[][][] trackIndices;
   private final Format[][][] trackFormats;
   private final Handler handler;
   private final HandlerThread internalPlaybackThread;
@@ -127,9 +125,8 @@ import java.util.concurrent.atomic.AtomicInteger;
     standaloneMediaClock = new StandaloneMediaClock();
     pendingSeekCount = new AtomicInteger();
     enabledRenderers = new ArrayList<>(renderers.length);
-    groupIndices = new int[renderers.length][];
+    trackSelections = new TrackSelection[renderers.length][];
     trackFormats = new Format[renderers.length][][];
-    trackIndices = new int[renderers.length][][];
     // Note: The documentation for Process.THREAD_PRIORITY_AUDIO that states "Applications can
     // not normally change to this priority" is incorrect.
     internalPlaybackThread = new PriorityHandlerThread("ExoPlayerImplInternal:Handler",
@@ -300,17 +297,15 @@ import java.util.concurrent.atomic.AtomicInteger;
       return;
     }
 
-    this.durationUs = source.getDurationUs();
+    durationUs = source.getDurationUs();
-    this.bufferedPositionUs = source.getBufferedPositionUs();
+    bufferedPositionUs = source.getBufferedPositionUs();
-
+    TrackGroup[] trackGroups = source.getTrackGroups();
-    boolean allRenderersEnded = true;
-    boolean allRenderersReadyOrEnded = true;
 
     // The maximum number of tracks that one renderer can support is the total number of tracks in
     // all groups, plus possibly one adaptive track per group.
-    int maxTrackCount = source.getTrackGroupCount();
+    int maxTrackCount = trackGroups.length;
-    for (int groupIndex = 0; groupIndex < source.getTrackGroupCount(); groupIndex++) {
+    for (int groupIndex = 0; groupIndex < trackGroups.length; groupIndex++) {
-      maxTrackCount += source.getTrackGroup(groupIndex).length;
+      maxTrackCount += trackGroups[groupIndex].length;
     }
     // Construct tracks for each renderer.
     Format[][] externalTrackFormats = new Format[renderers.length][];
@@ -318,11 +313,10 @@ import java.util.concurrent.atomic.AtomicInteger;
       TrackRenderer renderer = renderers[rendererIndex];
       int rendererTrackCount = 0;
       Format[] rendererExternalTrackFormats = new Format[maxTrackCount];
-      int[] rendererTrackGroups = new int[maxTrackCount];
+      TrackSelection[] rendererTrackSelections = new TrackSelection[maxTrackCount];
-      int[][] rendererTrackIndices = new int[maxTrackCount][];
       Format[][] rendererTrackFormats = new Format[maxTrackCount][];
-      for (int groupIndex = 0; groupIndex < source.getTrackGroupCount(); groupIndex++) {
+      for (int groupIndex = 0; groupIndex < trackGroups.length; groupIndex++) {
-        TrackGroup trackGroup = source.getTrackGroup(groupIndex);
+        TrackGroup trackGroup = trackGroups[groupIndex];
         // TODO[REFACTOR]: This should check that the renderer is capable of adaptive playback, in
         // addition to checking that the group is adaptive.
         if (trackGroup.adaptive) {
@@ -331,7 +325,7 @@ import java.util.concurrent.atomic.AtomicInteger;
           int[] adaptiveTrackIndices = new int[trackGroup.length];
           Format[] adaptiveTrackFormats = new Format[trackGroup.length];
           for (int trackIndex = 0; trackIndex < trackGroup.length; trackIndex++) {
-            Format trackFormat = source.getTrackGroup(groupIndex).getFormat(trackIndex);
+            Format trackFormat = trackGroup.getFormat(trackIndex);
             if ((renderer.supportsFormat(trackFormat) & TrackRenderer.FORMAT_SUPPORT_MASK)
                 == TrackRenderer.FORMAT_HANDLED) {
               adaptiveTrackIndices[adaptiveTrackIndexCount] = trackIndex;
@@ -340,9 +334,8 @@ import java.util.concurrent.atomic.AtomicInteger;
           }
           if (adaptiveTrackIndexCount > 1) {
             // We succeeded in building an adaptive track.
-            rendererTrackGroups[rendererTrackCount] = groupIndex;
+            rendererTrackSelections[rendererTrackCount] = new TrackSelection(groupIndex,
-            rendererTrackIndices[rendererTrackCount] =
+                Arrays.copyOf(adaptiveTrackIndices, adaptiveTrackIndexCount));
-                Arrays.copyOf(adaptiveTrackIndices, adaptiveTrackIndexCount);
             rendererTrackFormats[rendererTrackCount] =
                 Arrays.copyOf(adaptiveTrackFormats, adaptiveTrackIndexCount);
             rendererExternalTrackFormats[rendererTrackCount++] = Format.createSampleFormat(
@@ -350,30 +343,32 @@ import java.util.concurrent.atomic.AtomicInteger;
           }
         }
         for (int trackIndex = 0; trackIndex < trackGroup.length; trackIndex++) {
-          Format trackFormat = source.getTrackGroup(groupIndex).getFormat(trackIndex);
+          Format trackFormat = trackGroup.getFormat(trackIndex);
           if ((renderer.supportsFormat(trackFormat) & TrackRenderer.FORMAT_SUPPORT_MASK)
               == TrackRenderer.FORMAT_HANDLED) {
-            rendererTrackGroups[rendererTrackCount] = groupIndex;
+            rendererTrackSelections[rendererTrackCount] = new TrackSelection(groupIndex,
-            rendererTrackIndices[rendererTrackCount] = new int[] {trackIndex};
+                trackIndex);
             rendererTrackFormats[rendererTrackCount] = new Format[] {trackFormat};
             rendererExternalTrackFormats[rendererTrackCount++] = trackFormat;
           }
         }
       }
-      groupIndices[rendererIndex] = Arrays.copyOf(rendererTrackGroups, rendererTrackCount);
+      trackSelections[rendererIndex] = Arrays.copyOf(rendererTrackSelections, rendererTrackCount);
-      trackIndices[rendererIndex] = Arrays.copyOf(rendererTrackIndices, rendererTrackCount);
       trackFormats[rendererIndex] = Arrays.copyOf(rendererTrackFormats, rendererTrackCount);
       externalTrackFormats[rendererIndex] = Arrays.copyOf(rendererExternalTrackFormats,
           rendererTrackCount);
     }
 
+    boolean allRenderersEnded = true;
+    boolean allRenderersReadyOrEnded = true;
+
     // Enable renderers where appropriate.
     for (int rendererIndex = 0; rendererIndex < renderers.length; rendererIndex++) {
       TrackRenderer renderer = renderers[rendererIndex];
       int trackIndex = selectedTrackIndices[rendererIndex];
-      if (0 <= trackIndex && trackIndex < trackIndices[rendererIndex].length) {
+      if (0 <= trackIndex && trackIndex < trackSelections[rendererIndex].length) {
-        TrackStream trackStream = source.enable(groupIndices[rendererIndex][trackIndex],
+        TrackStream trackStream = source.enable(trackSelections[rendererIndex][trackIndex],
-            trackIndices[rendererIndex][trackIndex], positionUs);
+            positionUs);
         renderer.enable(trackFormats[rendererIndex][trackIndex], trackStream, positionUs, false);
         enabledRenderers.add(renderer);
         allRenderersEnded = allRenderersEnded && renderer.isEnded();
@@ -572,7 +567,7 @@ import java.util.concurrent.atomic.AtomicInteger;
       resetRendererInternal(renderers[i]);
     }
     enabledRenderers.clear();
-    Arrays.fill(trackIndices, null);
+    Arrays.fill(trackSelections, null);
     source = null;
   }
 
@@ -622,13 +617,13 @@ import java.util.concurrent.atomic.AtomicInteger;
 
     TrackRenderer renderer = renderers[rendererIndex];
     int rendererState = renderer.getState();
-    if (trackIndices[rendererIndex].length == 0) {
+    if (trackSelections[rendererIndex].length == 0) {
       return;
     }
 
     boolean isEnabled = rendererState == TrackRenderer.STATE_ENABLED
         || rendererState == TrackRenderer.STATE_STARTED;
-    boolean shouldEnable = 0 <= trackIndex && trackIndex < trackIndices[rendererIndex].length;
+    boolean shouldEnable = 0 <= trackIndex && trackIndex < trackSelections[rendererIndex].length;
 
     if (isEnabled) {
       // The renderer is currently enabled. We need to disable it, so that we can either re-enable
@@ -650,8 +645,8 @@ import java.util.concurrent.atomic.AtomicInteger;
       boolean playing = playWhenReady && state == ExoPlayer.STATE_READY;
       // Consider as joining if the renderer was previously disabled, but not when switching tracks.
       boolean joining = !isEnabled && playing;
-      TrackStream trackStream = source.enable(groupIndices[rendererIndex][trackIndex],
+      TrackStream trackStream = source.enable(trackSelections[rendererIndex][trackIndex],
-          trackIndices[rendererIndex][trackIndex], positionUs);
+          positionUs);
       renderer.enable(trackFormats[rendererIndex][trackIndex], trackStream, positionUs, joining);
       enabledRenderers.add(renderer);
       if (playing) {

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

@@ -156,13 +156,8 @@ public final class FrameworkSampleSource implements SampleSource {
   }
 
   @Override
-  public int getTrackGroupCount() {
+  public TrackGroup[] getTrackGroups() {
-    return tracks.length;
+    return tracks;
-  }
-
-  @Override
-  public TrackGroup getTrackGroup(int group) {
-    return tracks[group];
   }
 
   @Override
@@ -171,14 +166,17 @@ public final class FrameworkSampleSource implements SampleSource {
   }
 
   @Override
-  public TrackStream enable(int group, int[] track, long positionUs) {
+  public TrackStream enable(TrackSelection selection, long positionUs) {
     Assertions.checkState(prepared);
-    Assertions.checkState(trackStates[group] == TRACK_STATE_DISABLED);
+    Assertions.checkState(selection.tracks.length == 1);
+    Assertions.checkState(selection.tracks[0] == 0);
+    int track = selection.group;
+    Assertions.checkState(trackStates[track] == TRACK_STATE_DISABLED);
     enabledTrackCount++;
-    trackStates[group] = TRACK_STATE_ENABLED;
+    trackStates[track] = TRACK_STATE_ENABLED;
-    extractor.selectTrack(group);
+    extractor.selectTrack(track);
     seekToUsInternal(positionUs, positionUs != 0);
-    return new TrackStreamImpl(group);
+    return new TrackStreamImpl(track);
   }
 
   /* package */ long readReset(int track) {

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

@@ -16,7 +16,6 @@
 package com.google.android.exoplayer;
 
 import com.google.android.exoplayer.MediaCodecUtil.DecoderQueryException;
-import com.google.android.exoplayer.SampleSource.TrackStream;
 import com.google.android.exoplayer.drm.DrmInitData;
 import com.google.android.exoplayer.drm.DrmSessionManager;
 import com.google.android.exoplayer.util.Assertions;

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

@@ -16,7 +16,6 @@
 package com.google.android.exoplayer;
 
 import com.google.android.exoplayer.MediaCodecUtil.DecoderQueryException;
-import com.google.android.exoplayer.SampleSource.TrackStream;
 import com.google.android.exoplayer.drm.DrmSessionManager;
 import com.google.android.exoplayer.util.MimeTypes;
 import com.google.android.exoplayer.util.TraceUtil;

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

@@ -48,7 +48,7 @@ public class MultiSampleSource implements SampleSource {
       this.durationUs = C.UNKNOWN_TIME_US;
       int totalTrackGroupCount = 0;
       for (int i = 0; i < sources.length; i++) {
-        totalTrackGroupCount += sources[i].getTrackGroupCount();
+        totalTrackGroupCount += sources[i].getTrackGroups().length;
         if (sources[i].getDurationUs() > durationUs) {
           durationUs = sources[i].getDurationUs();
         }
@@ -56,9 +56,9 @@ public class MultiSampleSource implements SampleSource {
       tracks = new TrackGroup[totalTrackGroupCount];
       int trackGroupIndex = 0;
       for (int i = 0; i < sources.length; i++) {
-        int sourceTrackGroupCount = sources[i].getTrackGroupCount();
+        int sourceTrackGroupCount = sources[i].getTrackGroups().length;
         for (int j = 0; j < sourceTrackGroupCount; j++) {
-          tracks[trackGroupIndex++] = sources[i].getTrackGroup(j);
+          tracks[trackGroupIndex++] = sources[i].getTrackGroups()[j];
         }
       }
     }
@@ -71,19 +71,15 @@ public class MultiSampleSource implements SampleSource {
   }
 
   @Override
-  public int getTrackGroupCount() {
+  public TrackGroup[] getTrackGroups() {
-    return tracks.length;
+    return tracks;
   }
 
   @Override
-  public TrackGroup getTrackGroup(int group) {
+  public TrackStream enable(TrackSelection selection, long positionUs) {
-    return tracks[group];
+    Pair<Integer, Integer> sourceAndGroup = getSourceAndTrackGroupIndices(selection.group);
-  }
+    return sources[sourceAndGroup.first].enable(
-
+        new TrackSelection(sourceAndGroup.second, selection.tracks), positionUs);
-  @Override
-  public TrackStream enable(int group, int[] tracks, long positionUs) {
-    Pair<Integer, Integer> sourceAndGroup = getSourceAndTrackGroupIndices(group);
-    return sources[sourceAndGroup.first].enable(sourceAndGroup.second, tracks, positionUs);
   }
 
   @Override
@@ -132,7 +128,7 @@ public class MultiSampleSource implements SampleSource {
   private Pair<Integer, Integer> getSourceAndTrackGroupIndices(int group) {
     int totalTrackGroupCount = 0;
     for (int i = 0; i < sources.length; i++) {
-      int sourceTrackGroupCount = sources[i].getTrackGroupCount();
+      int sourceTrackGroupCount = sources[i].getTrackGroups().length;
       if (group < totalTrackGroupCount + sourceTrackGroupCount) {
         return Pair.create(i, group - totalTrackGroupCount);
       }

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

@@ -52,23 +52,13 @@ public interface SampleSource {
   long getDurationUs();
 
   /**
-   * Returns the number of track groups exposed by the source.
+   * Returns the {@link TrackGroup}s exposed by the source.
    * <p>
    * This method should only be called after the source has been prepared.
    *
-   * @return The number of track groups exposed by the source.
+   * @return The {@link TrackGroup}s.
    */
-  public int getTrackGroupCount();
+  public TrackGroup[] getTrackGroups();
-
-  /**
-   * Returns the {@link TrackGroup} at the specified index.
-   * <p>
-   * This method should only be called after the source has been prepared.
-   *
-   * @int group The group index.
-   * @return The corresponding {@link TrackGroup}.
-   */
-  public TrackGroup getTrackGroup(int group);
 
   /**
    * Indicates to the source that it should continue buffering data for its enabled tracks.
@@ -101,19 +91,19 @@ public interface SampleSource {
   void seekToUs(long positionUs);
 
   /**
-   * Enables the specified group to read the specified tracks. A {@link TrackStream} is returned
+   * Enables the source to read a track defined by a {@link TrackSelection}. A {@link TrackStream}
-   * through which the enabled track's data can be read.
+   * is returned through which the track's data can be read.
    * <p>
-   * This method should only be called after the source has been prepared, and when the specified
+   * This method should only be called after the source has been prepared, and when there are no
-   * group is disabled. Note that {@code tracks.length} is only permitted to be greater than one
+   * other enabled tracks with the same {@link TrackSelection#group} index. Note that
-   * if {@link TrackGroup#adaptive} is true for the group.
+   * {@code TrackSelection#tracks} must be of length 1 unless {@link TrackGroup#adaptive} is true
+   * for the group.
    *
-   * @param group The group index.
+   * @param selection Defines the track.
-   * @param tracks The track indices.
    * @param positionUs The current playback position in microseconds.
    * @return A {@link TrackStream} from which the enabled track's data can be read.
    */
-  public TrackStream enable(int group, int[] tracks, long positionUs);
+  public TrackStream enable(TrackSelection selection, long positionUs);
 
   /**
    * Releases the source.
@@ -122,77 +112,4 @@ public interface SampleSource {
    */
   void release();
 
-  /**
-   * A stream of data corresponding to a single {@link SampleSource} track.
-   */
-  interface TrackStream {
-
-    /**
-     * The end of stream has been reached.
-     */
-    static final int END_OF_STREAM = -1;
-    /**
-     * Nothing was read.
-     */
-    static final int NOTHING_READ = -2;
-    /**
-     * A sample was read.
-     */
-    static final int SAMPLE_READ = -3;
-    /**
-     * A format was read.
-     */
-    static final int FORMAT_READ = -4;
-    /**
-     * Returned from {@link #readReset()} to indicate no reset is required.
-     */
-    static final long NO_RESET = Long.MIN_VALUE;
-
-    /**
-     * Returns whether data is available to be read.
-     * <p>
-     * Note: If the stream has ended then {@link #END_OF_STREAM} can always be read from
-     * {@link #readData(FormatHolder, SampleHolder)}. Hence an ended stream is always ready.
-     *
-     * @return True if data is available to be read. False otherwise.
-     */
-    boolean isReady();
-
-    /**
-     * If there's an underlying error preventing data from being read, it's thrown by this method.
-     * If not, this method does nothing.
-     *
-     * @throws IOException The underlying error.
-     */
-    void maybeThrowError() throws IOException;
-
-    /**
-     * Attempts to read a pending reset.
-     *
-     * @return If a reset was read then the position after the reset. Else {@link #NO_RESET}.
-     */
-    long readReset();
-
-    /**
-     * Attempts to read the next format or sample.
-     * <p>
-     * This method will always return {@link #NOTHING_READ} in the case that there's a pending
-     * discontinuity to be read from {@link #readReset} for the specified track.
-     *
-     * @param formatHolder A {@link FormatHolder} to populate in the case of a new format.
-     * @param sampleHolder A {@link SampleHolder} to populate in the case of a new sample. If the
-     *     caller requires the sample data then it must ensure that {@link SampleHolder#data}
-     *     references a valid output buffer.
-     * @return The result, which can be {@link #END_OF_STREAM}, {@link #NOTHING_READ},
-     *     {@link #FORMAT_READ} or {@link #SAMPLE_READ}.
-     */
-    int readData(FormatHolder formatHolder, SampleHolder sampleHolder);
-
-    /**
-     * Disables the track.
-     */
-    void disable();
-
-  }
-
 }

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

@@ -15,7 +15,6 @@
  */
 package com.google.android.exoplayer;
 
-import com.google.android.exoplayer.SampleSource.TrackStream;
 import com.google.android.exoplayer.util.Assertions;
 
 import java.io.IOException;

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

@@ -15,7 +15,6 @@
  */
 package com.google.android.exoplayer;
 
-import com.google.android.exoplayer.SampleSource.TrackStream;
 import com.google.android.exoplayer.upstream.DataSource;
 import com.google.android.exoplayer.upstream.DataSpec;
 import com.google.android.exoplayer.upstream.Loader;
@@ -53,7 +52,7 @@ public final class SingleSampleSource implements SampleSource, TrackStream, Load
   private final Format format;
   private final long durationUs;
   private final int minLoadableRetryCount;
-  private final TrackGroup tracks;
+  private final TrackGroup[] trackGroups;
 
   private int state;
   private byte[] sampleData;
@@ -76,7 +75,7 @@ public final class SingleSampleSource implements SampleSource, TrackStream, Load
     this.format = format;
     this.durationUs = durationUs;
     this.minLoadableRetryCount = minLoadableRetryCount;
-    tracks = new TrackGroup(format);
+    trackGroups = new TrackGroup[] {new TrackGroup(format)};
     sampleData = new byte[INITIAL_SAMPLE_SIZE];
   }
 
@@ -106,17 +105,12 @@ public final class SingleSampleSource implements SampleSource, TrackStream, Load
   }
 
   @Override
-  public int getTrackGroupCount() {
+  public TrackGroup[] getTrackGroups() {
-    return 1;
+    return trackGroups;
   }
 
   @Override
-  public TrackGroup getTrackGroup(int group) {
+  public TrackStream enable(TrackSelection selection, long positionUs) {
-    return tracks;
-  }
-
-  @Override
-  public TrackStream enable(int group, int[] tracks, long positionUs) {
     state = STATE_SEND_FORMAT;
     clearCurrentLoadableException();
     maybeStartLoading();

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

@@ -15,8 +15,6 @@
  */
 package com.google.android.exoplayer;
 
-import com.google.android.exoplayer.SampleSource.TrackStream;
-
 /**
  * Defines a group of tracks exposed by a {@link SampleSource}.
  * <p>

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

@@ -16,7 +16,6 @@
 package com.google.android.exoplayer;
 
 import com.google.android.exoplayer.ExoPlayer.ExoPlayerComponent;
-import com.google.android.exoplayer.SampleSource.TrackStream;
 import com.google.android.exoplayer.util.Assertions;
 import com.google.android.exoplayer.util.MimeTypes;
 

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

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer;
+
+/**
+ * Defines a track selection.
+ */
+public final class TrackSelection {
+
+  /**
+   * The index of the {@link TrackGroup}.
+   */
+  public final int group;
+  /**
+   * The indices of the individual tracks within the {@link TrackGroup}.
+   */
+  public final int[] tracks;
+
+  /**
+   * @param group The index of the {@link TrackGroup}.
+   * @param tracks The indices of the individual tracks within the {@link TrackGroup}.
+   */
+  public TrackSelection(int group, int... tracks) {
+    this.group = group;
+    this.tracks = tracks;
+  }
+
+}

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

@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer;
+
+import java.io.IOException;
+
+/**
+ * A stream of media data.
+ */
+public interface TrackStream {
+
+  /**
+   * The end of stream has been reached.
+   */
+  int END_OF_STREAM = -1;
+  /**
+   * Nothing was read.
+   */
+  int NOTHING_READ = -2;
+  /**
+   * A sample was read.
+   */
+  int SAMPLE_READ = -3;
+  /**
+   * A format was read.
+   */
+  int FORMAT_READ = -4;
+  /**
+   * Returned from {@link #readReset()} to indicate no reset is required.
+   */
+  long NO_RESET = Long.MIN_VALUE;
+
+  /**
+   * Returns whether data is available to be read.
+   * <p>
+   * Note: If the stream has ended then {@link #END_OF_STREAM} can always be read from
+   * {@link #readData(FormatHolder, SampleHolder)}. Hence an ended stream is always ready.
+   *
+   * @return True if data is available to be read. False otherwise.
+   */
+  boolean isReady();
+
+  /**
+   * If there's an underlying error preventing data from being read, it's thrown by this method.
+   * If not, this method does nothing.
+   *
+   * @throws IOException The underlying error.
+   */
+  void maybeThrowError() throws IOException;
+
+  /**
+   * Attempts to read a pending reset.
+   *
+   * @return If a reset was read then the position after the reset. Else {@link #NO_RESET}.
+   */
+  long readReset();
+
+  /**
+   * Attempts to read the next format or sample.
+   * <p>
+   * This method will always return {@link #NOTHING_READ} in the case that there's a pending
+   * discontinuity to be read from {@link #readReset} for the specified track.
+   *
+   * @param formatHolder A {@link FormatHolder} to populate in the case of a new format.
+   * @param sampleHolder A {@link SampleHolder} to populate in the case of a new sample. If the
+   *     caller requires the sample data then it must ensure that {@link SampleHolder#data}
+   *     references a valid output buffer.
+   * @return The result, which can be {@link #END_OF_STREAM}, {@link #NOTHING_READ},
+   *     {@link #FORMAT_READ} or {@link #SAMPLE_READ}.
+   */
+  int readData(FormatHolder formatHolder, SampleHolder sampleHolder);
+
+  /**
+   * Disables the track.
+   */
+  void disable();
+
+}

library/src/main/java/com/google/android/exoplayer/chunk/BaseChunkSampleSourceEventListener.java

@@ -18,7 +18,7 @@ package com.google.android.exoplayer.chunk;
 import com.google.android.exoplayer.C;
 import com.google.android.exoplayer.Format;
 import com.google.android.exoplayer.SampleSource;
-import com.google.android.exoplayer.SampleSource.TrackStream;
+import com.google.android.exoplayer.TrackStream;
 
 import java.io.IOException;
 

library/src/main/java/com/google/android/exoplayer/chunk/ChunkSampleSource.java

@@ -21,8 +21,9 @@ import com.google.android.exoplayer.FormatHolder;
 import com.google.android.exoplayer.LoadControl;
 import com.google.android.exoplayer.SampleHolder;
 import com.google.android.exoplayer.SampleSource;
-import com.google.android.exoplayer.SampleSource.TrackStream;
 import com.google.android.exoplayer.TrackGroup;
+import com.google.android.exoplayer.TrackSelection;
+import com.google.android.exoplayer.TrackStream;
 import com.google.android.exoplayer.extractor.DefaultTrackOutput;
 import com.google.android.exoplayer.upstream.Loader;
 import com.google.android.exoplayer.upstream.Loader.Loadable;
@@ -77,6 +78,7 @@ public class ChunkSampleSource implements SampleSource, TrackStream, Loader.Call
   private long lastPerformedBufferOperation;
   private boolean pendingReset;
 
+  private TrackGroup[] trackGroups;
   private long durationUs;
   private Loader loader;
   private boolean loadingFinished;
@@ -156,6 +158,9 @@ public class ChunkSampleSource implements SampleSource, TrackStream, Loader.Call
     TrackGroup trackGroup = chunkSource.getTracks();
     if (trackGroup.length > 0) {
       loader = new Loader("Loader:" + trackGroup.getFormat(0).containerMimeType);
+      trackGroups = new TrackGroup[] {trackGroup};
+    } else {
+      trackGroups = new TrackGroup[0];
     }
     state = STATE_PREPARED;
     return true;
@@ -172,22 +177,17 @@ public class ChunkSampleSource implements SampleSource, TrackStream, Loader.Call
   }
 
   @Override
-  public int getTrackGroupCount() {
+  public TrackGroup[] getTrackGroups() {
-    return 1;
-  }
-
-  @Override
-  public TrackGroup getTrackGroup(int group) {
     Assertions.checkState(state != STATE_IDLE);
-    return chunkSource.getTracks();
+    return trackGroups;
   }
 
   @Override
-  public TrackStream enable(int group, int[] tracks, long positionUs) {
+  public TrackStream enable(TrackSelection selection, long positionUs) {
     Assertions.checkState(state == STATE_PREPARED);
     Assertions.checkState(enabledTrackCount++ == 0);
     state = STATE_ENABLED;
-    chunkSource.enable(tracks);
+    chunkSource.enable(selection.tracks);
     loadControl.register(this, bufferSizeContribution);
     downstreamFormat = null;
     downstreamSampleFormat = null;

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

@@ -21,6 +21,8 @@ import com.google.android.exoplayer.ParserException;
 import com.google.android.exoplayer.SampleHolder;
 import com.google.android.exoplayer.SampleSource;
 import com.google.android.exoplayer.TrackGroup;
+import com.google.android.exoplayer.TrackSelection;
+import com.google.android.exoplayer.TrackStream;
 import com.google.android.exoplayer.drm.DrmInitData;
 import com.google.android.exoplayer.upstream.Allocator;
 import com.google.android.exoplayer.upstream.DataSource;
@@ -288,23 +290,21 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
   }
 
   @Override
-  public int getTrackGroupCount() {
+  public TrackGroup[] getTrackGroups() {
-    return tracks.length;
+    return tracks;
   }
 
   @Override
-  public TrackGroup getTrackGroup(int group) {
+  public TrackStream enable(TrackSelection selection, long positionUs) {
-    return tracks[group];
-  }
-
-  @Override
-  public TrackStream enable(int group, int[] tracks, long positionUs) {
     Assertions.checkState(prepared);
-    Assertions.checkState(!trackEnabledStates[group]);
+    Assertions.checkState(selection.tracks.length == 1);
+    Assertions.checkState(selection.tracks[0] == 0);
+    int track = selection.group;
+    Assertions.checkState(!trackEnabledStates[track]);
     enabledTrackCount++;
-    trackEnabledStates[group] = true;
+    trackEnabledStates[track] = true;
-    pendingMediaFormat[group] = true;
+    pendingMediaFormat[track] = true;
-    pendingResets[group] = false;
+    pendingResets[track] = false;
     if (enabledTrackCount == 1) {
       // Treat all enables in non-seekable media as being from t=0.
       positionUs = !seekMap.isSeekable() ? 0 : positionUs;
@@ -312,7 +312,7 @@ public final class ExtractorSampleSource implements SampleSource, ExtractorOutpu
       lastSeekPositionUs = positionUs;
       restartFrom(positionUs);
     }
-    return new TrackStreamImpl(group);
+    return new TrackStreamImpl(track);
   }
 
   /* package */ void disable(int track) {

library/src/main/java/com/google/android/exoplayer/hls/HlsSampleSource.java

@@ -22,6 +22,8 @@ import com.google.android.exoplayer.LoadControl;
 import com.google.android.exoplayer.SampleHolder;
 import com.google.android.exoplayer.SampleSource;
 import com.google.android.exoplayer.TrackGroup;
+import com.google.android.exoplayer.TrackSelection;
+import com.google.android.exoplayer.TrackStream;
 import com.google.android.exoplayer.chunk.BaseChunkSampleSourceEventListener;
 import com.google.android.exoplayer.chunk.Chunk;
 import com.google.android.exoplayer.chunk.ChunkOperationHolder;
@@ -179,19 +181,16 @@ public final class HlsSampleSource implements SampleSource, Loader.Callback {
   }
 
   @Override
-  public int getTrackGroupCount() {
+  public TrackGroup[] getTrackGroups() {
-    return trackGroups.length;
+    Assertions.checkState(prepared);
+    return trackGroups;
   }
 
   @Override
-  public TrackGroup getTrackGroup(int group) {
+  public TrackStream enable(TrackSelection selection, long positionUs) {
-    Assertions.checkState(prepared);
-    return trackGroups[group];
-  }
-
-  @Override
-  public TrackStream enable(int group, int[] tracks, long positionUs) {
     Assertions.checkState(prepared);
+    int group = selection.group;
+    int[] tracks = selection.tracks;
     setTrackGroupEnabledState(group, true);
     downstreamSampleFormats[group] = null;
     pendingResets[group] = false;

library/src/main/java/com/google/android/exoplayer/metadata/MetadataTrackRenderer.java

@@ -19,9 +19,9 @@ import com.google.android.exoplayer.ExoPlaybackException;
 import com.google.android.exoplayer.Format;
 import com.google.android.exoplayer.FormatHolder;
 import com.google.android.exoplayer.SampleHolder;
-import com.google.android.exoplayer.SampleSource.TrackStream;
 import com.google.android.exoplayer.SampleSourceTrackRenderer;
 import com.google.android.exoplayer.TrackRenderer;
+import com.google.android.exoplayer.TrackStream;
 import com.google.android.exoplayer.util.Assertions;
 
 import android.os.Handler;

library/src/main/java/com/google/android/exoplayer/text/TextTrackRenderer.java

@@ -19,9 +19,9 @@ import com.google.android.exoplayer.ExoPlaybackException;
 import com.google.android.exoplayer.Format;
 import com.google.android.exoplayer.FormatHolder;
 import com.google.android.exoplayer.SampleHolder;
-import com.google.android.exoplayer.SampleSource.TrackStream;
 import com.google.android.exoplayer.SampleSourceTrackRenderer;
 import com.google.android.exoplayer.TrackRenderer;
+import com.google.android.exoplayer.TrackStream;
 import com.google.android.exoplayer.util.Assertions;
 
 import android.annotation.TargetApi;

library/src/main/java/com/google/android/exoplayer/text/eia608/Eia608TrackRenderer.java

@@ -20,9 +20,9 @@ import com.google.android.exoplayer.ExoPlaybackException;
 import com.google.android.exoplayer.Format;
 import com.google.android.exoplayer.FormatHolder;
 import com.google.android.exoplayer.SampleHolder;
-import com.google.android.exoplayer.SampleSource.TrackStream;
 import com.google.android.exoplayer.SampleSourceTrackRenderer;
 import com.google.android.exoplayer.TrackRenderer;
+import com.google.android.exoplayer.TrackStream;
 import com.google.android.exoplayer.text.Cue;
 import com.google.android.exoplayer.text.TextRenderer;
 import com.google.android.exoplayer.util.Assertions;