Expose seek window + start position for SmoothStreaming

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=129867969

library/src/main/java/com/google/android/exoplayer2/source/SinglePeriodTimeline.java

@@ -19,18 +19,29 @@ import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.util.Assertions;
 
 /**
- * A {@link Timeline} consisting of a single period.
+ * A {@link Timeline} consisting of a single period and seek window.
  */
 public final class SinglePeriodTimeline implements Timeline {
 
   /**
-   * Returns a new timeline with one period of unknown duration and no seek window.
+   * Returns a new timeline with one period of unknown duration and an empty seek window.
    *
    * @param id The identifier for the period.
    * @return A new timeline with one period of unknown duration.
    */
   public static Timeline createNonFinalTimeline(Object id) {
-    return new SinglePeriodTimeline(id, false, C.UNSET_TIME_US);
+    return new SinglePeriodTimeline(id, false, C.UNSET_TIME_US, SeekWindow.UNSEEKABLE);
+  }
+
+  /**
+   * Returns a new timeline with one period of unknown duration and the specified seek window.
+   *
+   * @param id The identifier for the period.
+   * @param seekWindow The seek window.
+   * @return A new timeline with one period of unknown duration.
+   */
+  public static Timeline createNonFinalTimeline(Object id, SeekWindow seekWindow) {
+    return new SinglePeriodTimeline(id, false, C.UNSET_TIME_US, seekWindow);
   }
 
   /**
@@ -59,14 +70,13 @@ public final class SinglePeriodTimeline implements Timeline {
   private final Object id;
   private final boolean isFinal;
   private final long durationMs;
-  private final SeekWindow[] seekWindows;
+  private final SeekWindow seekWindow;
 
-  private SinglePeriodTimeline(Object id, boolean isFinal, long durationMs,
+  private SinglePeriodTimeline(Object id, boolean isFinal, long durationMs, SeekWindow seekWindow) {
-      SeekWindow... seekWindows) {
     this.id = Assertions.checkNotNull(id);
     this.isFinal = isFinal;
     this.durationMs = durationMs;
-    this.seekWindows = seekWindows;
+    this.seekWindow = seekWindow;
   }
 
   @Override
@@ -99,12 +109,12 @@ public final class SinglePeriodTimeline implements Timeline {
 
   @Override
   public int getSeekWindowCount() {
-    return seekWindows.length;
+    return 1;
   }
 
   @Override
   public SeekWindow getSeekWindow(int index) {
-    return seekWindows[index];
+    return seekWindow;
   }
 
 }

library/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaSource.java

@@ -24,9 +24,11 @@ import com.google.android.exoplayer2.source.AdaptiveMediaSourceEventListener;
 import com.google.android.exoplayer2.source.AdaptiveMediaSourceEventListener.EventDispatcher;
 import com.google.android.exoplayer2.source.MediaPeriod;
 import com.google.android.exoplayer2.source.MediaSource;
+import com.google.android.exoplayer2.source.SeekWindow;
 import com.google.android.exoplayer2.source.SinglePeriodTimeline;
 import com.google.android.exoplayer2.source.Timeline;
 import com.google.android.exoplayer2.source.smoothstreaming.manifest.SsManifest;
+import com.google.android.exoplayer2.source.smoothstreaming.manifest.SsManifest.StreamElement;
 import com.google.android.exoplayer2.source.smoothstreaming.manifest.SsManifestParser;
 import com.google.android.exoplayer2.upstream.DataSource;
 import com.google.android.exoplayer2.upstream.Loader;
@@ -45,6 +47,11 @@ public final class SsMediaSource implements MediaSource,
    * The default minimum number of times to retry loading data prior to failing.
    */
   public static final int DEFAULT_MIN_LOADABLE_RETRY_COUNT = 3;
+  /**
+   * The offset in microseconds subtracted from the live edge position when calculating the default
+   * position returned by {@link #getDefaultStartPosition(int)}.
+   */
+  private static final long LIVE_EDGE_OFFSET_US = 30000000;
 
   private static final int MINIMUM_MANIFEST_REFRESH_PERIOD_MS = 5000;
 
@@ -61,6 +68,7 @@ public final class SsMediaSource implements MediaSource,
 
   private long manifestLoadStartTimestamp;
   private SsManifest manifest;
+  private SeekWindow seekWindow;
 
   private Handler manifestRefreshHandler;
   private SsMediaPeriod period;
@@ -102,7 +110,14 @@ public final class SsMediaSource implements MediaSource,
 
   @Override
   public Position getDefaultStartPosition(int index) {
-    // TODO: Return the position of the live edge, if applicable.
+    if (seekWindow == null) {
+      return null;
+    }
+    if (manifest.isLive) {
+      long startPositionUs = Math.max(seekWindow.startTimeUs,
+          seekWindow.endTimeUs - LIVE_EDGE_OFFSET_US);
+      return new Position(0, startPositionUs);
+    }
     return Position.DEFAULT;
   }
 
@@ -144,9 +159,27 @@ public final class SsMediaSource implements MediaSource,
     } else {
       period.updateManifest(manifest);
     }
-    Timeline timeline = manifest.isLive || manifest.durationUs == C.UNSET_TIME_US
+    Timeline timeline;
-        ? SinglePeriodTimeline.createUnseekableFinalTimeline(this, C.UNSET_TIME_US)
+    if (manifest.isLive) {
-            : SinglePeriodTimeline.createSeekableFinalTimeline(this, manifest.durationUs);
+      long startTimeUs = Long.MAX_VALUE;
+      for (int i = 0; i < manifest.streamElements.length; i++) {
+        StreamElement element = manifest.streamElements[i];
+        if (element.chunkCount > 0) {
+          startTimeUs = Math.min(startTimeUs, element.getStartTimeUs(0));
+        }
+      }
+      if (startTimeUs == Long.MAX_VALUE) {
+        timeline = SinglePeriodTimeline.createNonFinalTimeline(this);
+      } else {
+        timeline = SinglePeriodTimeline.createNonFinalTimeline(this,
+            new SeekWindow(0, startTimeUs, 0, startTimeUs + manifest.dvrWindowLengthUs));
+      }
+    } else if (manifest.durationUs == C.UNSET_TIME_US) {
+      timeline = SinglePeriodTimeline.createUnseekableFinalTimeline(this, C.UNSET_TIME_US);
+    } else {
+      timeline = SinglePeriodTimeline.createSeekableFinalTimeline(this, manifest.durationUs);
+    }
+    seekWindow = timeline.getSeekWindow(0);
     sourceListener.onSourceInfoRefreshed(timeline, manifest);
     scheduleManifestRefresh();
   }