Add ClippingMediaSource.

ClippingMediaSource wraps a single period/window video-on-demand source and
exposes a specified time range within it.

Issue: #1988

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=141991215

library/src/androidTest/java/com/google/android/exoplayer2/source/ClippingMediaSourceTest.java

@@ -0,0 +1,143 @@
+/*
+ * Copyright (C) 2016 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.exoplayer2.source;
+
+import static org.mockito.Mockito.doAnswer;
+
+import android.test.InstrumentationTestCase;
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.ExoPlayer;
+import com.google.android.exoplayer2.Timeline;
+import com.google.android.exoplayer2.Timeline.Period;
+import com.google.android.exoplayer2.Timeline.Window;
+import com.google.android.exoplayer2.source.MediaSource.Listener;
+import com.google.android.exoplayer2.testutil.TestUtil;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+
+/**
+ * Unit tests for {@link ClippingMediaSource}.
+ */
+public final class ClippingMediaSourceTest extends InstrumentationTestCase {
+
+  private static final long TEST_PERIOD_DURATION_US = 1000000;
+  private static final long TEST_CLIP_AMOUNT_US = 300000;
+
+  @Mock
+  private MediaSource mockMediaSource;
+  private Timeline clippedTimeline;
+  private Window window;
+  private Period period;
+
+  @Override
+  protected void setUp() throws Exception {
+    TestUtil.setUpMockito(this);
+    window = new Timeline.Window();
+    period = new Timeline.Period();
+  }
+
+  public void testNoClipping() {
+    Timeline timeline = new SinglePeriodTimeline(C.msToUs(TEST_PERIOD_DURATION_US), true);
+
+    Timeline clippedTimeline = getClippedTimeline(timeline, 0, TEST_PERIOD_DURATION_US);
+
+    assertEquals(1, clippedTimeline.getWindowCount());
+    assertEquals(1, clippedTimeline.getPeriodCount());
+    assertEquals(TEST_PERIOD_DURATION_US, clippedTimeline.getWindow(0, window).getDurationUs());
+    assertEquals(TEST_PERIOD_DURATION_US, clippedTimeline.getPeriod(0, period).getDurationUs());
+  }
+
+  public void testClippingUnseekableWindowThrows() {
+    Timeline timeline = new SinglePeriodTimeline(C.msToUs(TEST_PERIOD_DURATION_US), false);
+
+    // If the unseekable window isn't clipped, clipping succeeds.
+    getClippedTimeline(timeline, 0, TEST_PERIOD_DURATION_US);
+    try {
+      // If the unseekable window is clipped, clipping fails.
+      getClippedTimeline(timeline, 1, TEST_PERIOD_DURATION_US);
+      fail("Expected clipping to fail.");
+    } catch (IllegalArgumentException e) {
+      // Expected.
+    }
+  }
+
+  public void testClippingStart() {
+    Timeline timeline = new SinglePeriodTimeline(C.msToUs(TEST_PERIOD_DURATION_US), true);
+
+    Timeline clippedTimeline = getClippedTimeline(timeline, TEST_CLIP_AMOUNT_US,
+        TEST_PERIOD_DURATION_US);
+    assertEquals(TEST_PERIOD_DURATION_US - TEST_CLIP_AMOUNT_US,
+        clippedTimeline.getWindow(0, window).getDurationUs());
+    assertEquals(TEST_PERIOD_DURATION_US - TEST_CLIP_AMOUNT_US,
+        clippedTimeline.getPeriod(0, period).getDurationUs());
+  }
+
+  public void testClippingEnd() {
+    Timeline timeline = new SinglePeriodTimeline(C.msToUs(TEST_PERIOD_DURATION_US), true);
+
+    Timeline clippedTimeline = getClippedTimeline(timeline, 0,
+        TEST_PERIOD_DURATION_US - TEST_CLIP_AMOUNT_US);
+    assertEquals(TEST_PERIOD_DURATION_US - TEST_CLIP_AMOUNT_US,
+        clippedTimeline.getWindow(0, window).getDurationUs());
+    assertEquals(TEST_PERIOD_DURATION_US - TEST_CLIP_AMOUNT_US,
+        clippedTimeline.getPeriod(0, period).getDurationUs());
+  }
+
+  public void testClippingStartAndEnd() {
+    Timeline timeline = new SinglePeriodTimeline(C.msToUs(TEST_PERIOD_DURATION_US), true);
+
+    Timeline clippedTimeline = getClippedTimeline(timeline, TEST_CLIP_AMOUNT_US,
+        TEST_PERIOD_DURATION_US - TEST_CLIP_AMOUNT_US * 2);
+    assertEquals(TEST_PERIOD_DURATION_US - TEST_CLIP_AMOUNT_US * 3,
+        clippedTimeline.getWindow(0, window).getDurationUs());
+    assertEquals(TEST_PERIOD_DURATION_US - TEST_CLIP_AMOUNT_US * 3,
+        clippedTimeline.getPeriod(0, period).getDurationUs());
+  }
+
+  /**
+   * Wraps the specified timeline in a {@link ClippingMediaSource} and returns the clipped timeline.
+   */
+  private Timeline getClippedTimeline(Timeline timeline, long startMs, long endMs) {
+    mockMediaSourceSourceWithTimeline(timeline);
+    new ClippingMediaSource(mockMediaSource, startMs, endMs).prepareSource(null, true,
+        new Listener() {
+          @Override
+          public void onSourceInfoRefreshed(Timeline timeline, Object manifest) {
+            clippedTimeline = timeline;
+          }
+        });
+    return clippedTimeline;
+  }
+
+  /**
+   * Returns a mock {@link MediaSource} with the specified {@link Timeline} in its source info.
+   */
+  private MediaSource mockMediaSourceSourceWithTimeline(final Timeline timeline) {
+    doAnswer(new Answer<Void>() {
+      @Override
+      public Void answer(InvocationOnMock invocation) throws Throwable {
+        MediaSource.Listener listener = (MediaSource.Listener) invocation.getArguments()[2];
+        listener.onSourceInfoRefreshed(timeline, null);
+        return null;
+      }
+    }).when(mockMediaSource).prepareSource(Mockito.any(ExoPlayer.class), Mockito.anyBoolean(),
+        Mockito.any(MediaSource.Listener.class));
+    return mockMediaSource;
+  }
+
+}

library/src/main/java/com/google/android/exoplayer2/BaseRenderer.java

@@ -70,8 +70,8 @@ public final int getState() {
   }
 
   @Override
-  public final void enable(Format[] formats, SampleStream stream, long positionUs,
-      boolean joining, long offsetUs) throws ExoPlaybackException {
+  public final void enable(Format[] formats, SampleStream stream, long positionUs, boolean joining,
+      long offsetUs) throws ExoPlaybackException {
     Assertions.checkState(state == STATE_DISABLED);
     state = STATE_ENABLED;
     onEnabled(joining);
@@ -200,8 +200,7 @@ protected void onStreamChanged(Format[] formats) throws ExoPlaybackException {
    * @param joining Whether this renderer is being enabled to join an ongoing playback.
    * @throws ExoPlaybackException If an error occurs.
    */
-  protected void onPositionReset(long positionUs, boolean joining)
-      throws ExoPlaybackException {
+  protected void onPositionReset(long positionUs, boolean joining) throws ExoPlaybackException {
     // Do nothing.
   }
 

library/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java

@@ -137,6 +137,14 @@ public SourceInfo(Timeline timeline, Object manifest, PlaybackInfo playbackInfo,
    */
   private static final int MAXIMUM_BUFFER_AHEAD_PERIODS = 100;
 
+  /**
+   * Offset added to all sample timestamps read by renderers to make them non-negative. This is
+   * provided for convenience of sources that may return negative timestamps due to prerolling
+   * samples from a keyframe before their first sample with timestamp zero, so it must be set to a
+   * value greater than or equal to the maximum key-frame interval in seekable periods.
+   */
+  private static final int RENDERER_TIMESTAMP_OFFSET_US = 60000000;
+
   private final Renderer[] renderers;
   private final RendererCapabilities[] rendererCapabilities;
   private final TrackSelector trackSelector;
@@ -637,7 +645,8 @@ private long seekToPeriodPosition(int periodIndex, long periodPositionUs)
   }
 
   private void resetRendererPosition(long periodPositionUs) throws ExoPlaybackException {
-    rendererPositionUs = playingPeriodHolder == null ? periodPositionUs
+    rendererPositionUs = playingPeriodHolder == null
+        ? periodPositionUs + RENDERER_TIMESTAMP_OFFSET_US
         : playingPeriodHolder.toRendererTime(periodPositionUs);
     standaloneMediaClock.setPositionUs(rendererPositionUs);
     for (Renderer renderer : enabledRenderers) {
@@ -1147,22 +1156,30 @@ private void updatePeriods() throws ExoPlaybackException, IOException {
       TrackSelectionArray oldTrackSelections = readingPeriodHolder.trackSelections;
       readingPeriodHolder = readingPeriodHolder.next;
       TrackSelectionArray newTrackSelections = readingPeriodHolder.trackSelections;
+
+      boolean initialDiscontinuity =
+          readingPeriodHolder.mediaPeriod.readDiscontinuity() != C.TIME_UNSET;
       for (int i = 0; i < renderers.length; i++) {
         Renderer renderer = renderers[i];
         TrackSelection oldSelection = oldTrackSelections.get(i);
         TrackSelection newSelection = newTrackSelections.get(i);
-        if (oldSelection != null) {
-          boolean isCurrentStreamFinal = renderer.isCurrentStreamFinal();
-          if (newSelection != null && !isCurrentStreamFinal) {
-            // Replace the renderer's SampleStream so the transition to playing the next period can
-            // be seamless.
+        if (oldSelection == null) {
+          // The renderer has no current stream and will be enabled when we play the next period.
+        } else if (initialDiscontinuity) {
+          // The new period starts with a discontinuity, so the renderer will play out all data then
+          // be disabled and re-enabled when it starts playing the next period.
+          renderer.setCurrentStreamFinal();
+        } else if (!renderer.isCurrentStreamFinal()) {
+          if (newSelection != null) {
+            // Replace the renderer's SampleStream so the transition to playing the next period
+            // can be seamless.
             Format[] formats = new Format[newSelection.length()];
             for (int j = 0; j < formats.length; j++) {
               formats[j] = newSelection.getFormat(j);
             }
             renderer.replaceStream(formats, readingPeriodHolder.sampleStreams[i],
                 readingPeriodHolder.getRendererOffset());
-          } else if (!isCurrentStreamFinal) {
+          } else {
             // The renderer will be disabled when transitioning to playing the next period. Mark the
             // SampleStream as final to play out any remaining data.
             renderer.setCurrentStreamFinal();
@@ -1228,7 +1245,8 @@ private void maybeUpdateLoadingPeriod() throws IOException {
       }
     }
 
-    long rendererPositionOffsetUs = loadingPeriodHolder == null ? newLoadingPeriodStartPositionUs
+    long rendererPositionOffsetUs = loadingPeriodHolder == null
+        ? newLoadingPeriodStartPositionUs + RENDERER_TIMESTAMP_OFFSET_US
         : (loadingPeriodHolder.getRendererOffset()
             + timeline.getPeriod(loadingPeriodHolder.index, period).getDurationUs());
     timeline.getPeriod(newLoadingPeriodIndex, period, true);

library/src/main/java/com/google/android/exoplayer2/Timeline.java

@@ -262,9 +262,24 @@ public static final class Window {
      */
     public int lastPeriodIndex;
 
-    private long defaultPositionUs;
-    private long durationUs;
-    private long positionInFirstPeriodUs;
+    /**
+     * The default position relative to the start of the window at which to begin playback, in
+     * microseconds. May be {@link C#TIME_UNSET} if and only if the window was populated with a
+     * non-zero default position projection, and if the specified projection cannot be performed
+     * whilst remaining within the bounds of the window.
+     */
+    public long defaultPositionUs;
+
+    /**
+     * The duration of this window in microseconds, or {@link C#TIME_UNSET} if unknown.
+     */
+    public long durationUs;
+
+    /**
+     * The position of the start of this window relative to the start of the first period belonging
+     * to it, in microseconds.
+     */
+    public long positionInFirstPeriodUs;
 
     /**
      * Sets the data held by this window.
@@ -363,7 +378,11 @@ public static final class Period {
      */
     public int windowIndex;
 
-    private long durationUs;
+    /**
+     * The duration of this period in microseconds, or {@link C#TIME_UNSET} if unknown.
+     */
+    public long durationUs;
+
     private long positionInWindowUs;
 
     /**