DASH: Correctly handle empty segment indices

Issue: #1865

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=147613244

library/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java

@@ -572,22 +572,28 @@ public final class DashMediaSource implements MediaSource {
       long availableStartTimeUs = 0;
       long availableEndTimeUs = Long.MAX_VALUE;
       boolean isIndexExplicit = false;
+      boolean seenEmptyIndex = false;
       for (int i = 0; i < adaptationSetCount; i++) {
         DashSegmentIndex index = period.adaptationSets.get(i).representations.get(0).getIndex();
         if (index == null) {
           return new PeriodSeekInfo(true, 0, durationUs);
         }
-        int firstSegmentNum = index.getFirstSegmentNum();
-        int lastSegmentNum = index.getLastSegmentNum(durationUs);
         isIndexExplicit |= index.isExplicit();
+        int segmentCount = index.getSegmentCount(durationUs);
+        if (segmentCount == 0) {
+          seenEmptyIndex = true;
+          availableStartTimeUs = 0;
+          availableEndTimeUs = 0;
+        } else if (!seenEmptyIndex) {
+          int firstSegmentNum = index.getFirstSegmentNum();
           long adaptationSetAvailableStartTimeUs = index.getTimeUs(firstSegmentNum);
           availableStartTimeUs = Math.max(availableStartTimeUs, adaptationSetAvailableStartTimeUs);
-        if (lastSegmentNum != DashSegmentIndex.INDEX_UNBOUNDED) {
+          if (segmentCount != DashSegmentIndex.INDEX_UNBOUNDED) {
+            int lastSegmentNum = firstSegmentNum + segmentCount - 1;
             long adaptationSetAvailableEndTimeUs = index.getTimeUs(lastSegmentNum)
                 + index.getDurationUs(lastSegmentNum, durationUs);
             availableEndTimeUs = Math.min(availableEndTimeUs, adaptationSetAvailableEndTimeUs);
-        } else {
+          }
-          // The available end time is unmodified, because this index is unbounded.
         }
       }
       return new PeriodSeekInfo(isIndexExplicit, availableStartTimeUs, availableEndTimeUs);
@@ -704,8 +710,8 @@ public final class DashMediaSource implements MediaSource {
       // not correspond to the start of a segment in both, but this is an edge case.
       DashSegmentIndex snapIndex = period.adaptationSets.get(videoAdaptationSetIndex)
           .representations.get(0).getIndex();
-      if (snapIndex == null) {
+      if (snapIndex == null || snapIndex.getSegmentCount(periodDurationUs) == 0) {
-        // Video adaptation set does not include an index for snapping.
+        // Video adaptation set does not include a non-empty index for snapping.
         return windowDefaultStartPositionUs;
       }
       int segmentNum = snapIndex.getSegmentNum(defaultStartPositionInPeriodUs, periodDurationUs);

library/src/main/java/com/google/android/exoplayer2/source/dash/DashSegmentIndex.java

@@ -26,12 +26,10 @@ public interface DashSegmentIndex {
   int INDEX_UNBOUNDED = -1;
 
   /**
-   * Returns the segment number of the segment containing a given media time.
+   * Returns {@code getFirstSegmentNum()} if the index has no segments or if the given media time is
-   * <p>
+   * earlier than the start of the first segment. Returns {@code getFirstSegmentNum() +
-   * If the given media time is outside the range of the index, then the returned segment number is
+   * getSegmentCount() - 1} if the given media time is later than the end of the last segment.
-   * clamped to {@link #getFirstSegmentNum()} (if the given media time is earlier the start of the
+   * Otherwise, returns the segment number of the segment containing the given media time.
-   * first segment) or {@link #getLastSegmentNum(long)} (if the given media time is later then the
-   * end of the last segment).
    *
    * @param timeUs The time in microseconds.
    * @param periodDurationUs The duration of the enclosing period in microseconds, or
@@ -74,7 +72,7 @@ public interface DashSegmentIndex {
   int getFirstSegmentNum();
 
   /**
-   * Returns the segment number of the last segment, or {@link #INDEX_UNBOUNDED}.
+   * Returns the number of segments in the index, or {@link #INDEX_UNBOUNDED}.
    * <p>
    * An unbounded index occurs if a dynamic manifest uses SegmentTemplate elements without a
    * SegmentTimeline element, and if the period duration is not yet known. In this case the caller
@@ -82,9 +80,9 @@ public interface DashSegmentIndex {
    *
    * @param periodDurationUs The duration of the enclosing period in microseconds, or
    *     {@link C#TIME_UNSET} if the period's duration is not yet known.
-   * @return The segment number of the last segment, or {@link #INDEX_UNBOUNDED}.
+   * @return The number of segments in the index, or {@link #INDEX_UNBOUNDED}.
    */
-  int getLastSegmentNum(long periodDurationUs);
+  int getSegmentCount(long periodDurationUs);
 
   /**
    * Returns true if segments are defined explicitly by the index.

library/src/main/java/com/google/android/exoplayer2/source/dash/DashWrappingSegmentIndex.java

@@ -39,8 +39,8 @@ import com.google.android.exoplayer2.source.dash.manifest.RangedUri;
   }
 
   @Override
-  public int getLastSegmentNum(long periodDurationUs) {
+  public int getSegmentCount(long periodDurationUs) {
-    return chunkIndex.length - 1;
+    return chunkIndex.length;
   }
 
   @Override

library/src/main/java/com/google/android/exoplayer2/source/dash/DefaultDashChunkSource.java

@@ -194,10 +194,16 @@ public class DefaultDashChunkSource implements DashChunkSource {
     }
 
     long nowUs = getNowUnixTimeUs();
+    int availableSegmentCount = representationHolder.getSegmentCount();
+    if (availableSegmentCount == 0) {
+      // The index doesn't define any segments.
+      out.endOfStream = !manifest.dynamic || (periodIndex < manifest.getPeriodCount() - 1);
+      return;
+    }
+
     int firstAvailableSegmentNum = representationHolder.getFirstSegmentNum();
-    int lastAvailableSegmentNum = representationHolder.getLastSegmentNum();
+    int lastAvailableSegmentNum;
-    boolean indexUnbounded = lastAvailableSegmentNum == DashSegmentIndex.INDEX_UNBOUNDED;
+    if (availableSegmentCount == DashSegmentIndex.INDEX_UNBOUNDED) {
-    if (indexUnbounded) {
       // The index is itself unbounded. We need to use the current time to calculate the range of
       // available segments.
       long liveEdgeTimeUs = nowUs - manifest.availabilityStartTime * 1000;
@@ -211,6 +217,8 @@ public class DefaultDashChunkSource implements DashChunkSource {
       // getSegmentNum(liveEdgeTimestampUs) will not be completed yet, so subtract one to get the
       // index of the last completed segment.
       lastAvailableSegmentNum = representationHolder.getSegmentNum(liveEdgeTimeInPeriodUs) - 1;
+    } else {
+      lastAvailableSegmentNum = firstAvailableSegmentNum + availableSegmentCount - 1;
     }
 
     int segmentNum;
@@ -268,12 +276,15 @@ public class DefaultDashChunkSource implements DashChunkSource {
         && ((InvalidResponseCodeException) e).responseCode == 404) {
       RepresentationHolder representationHolder =
           representationHolders[trackSelection.indexOf(chunk.trackFormat)];
-      int lastAvailableSegmentNum = representationHolder.getLastSegmentNum();
+      int segmentCount = representationHolder.getSegmentCount();
+      if (segmentCount != DashSegmentIndex.INDEX_UNBOUNDED && segmentCount != 0) {
+        int lastAvailableSegmentNum = representationHolder.getFirstSegmentNum() + segmentCount - 1;
         if (((MediaChunk) chunk).getNextChunkIndex() > lastAvailableSegmentNum) {
           missingLastSegment = true;
           return true;
         }
       }
+    }
     // Blacklist if appropriate.
     return ChunkedTrackBlacklistUtil.maybeBlacklistTrack(trackSelection,
         trackSelection.indexOf(chunk.trackFormat), e);
@@ -405,15 +416,20 @@ public class DefaultDashChunkSource implements DashChunkSource {
         return;
       }
 
-      int oldIndexLastSegmentNum = oldIndex.getLastSegmentNum(periodDurationUs);
+      int oldIndexSegmentCount = oldIndex.getSegmentCount(periodDurationUs);
+      if (oldIndexSegmentCount == 0) {
+        // Segment numbers cannot shift if the old index was empty.
+        return;
+      }
+
+      int oldIndexLastSegmentNum = oldIndex.getFirstSegmentNum() + oldIndexSegmentCount - 1;
       long oldIndexEndTimeUs = oldIndex.getTimeUs(oldIndexLastSegmentNum)
           + oldIndex.getDurationUs(oldIndexLastSegmentNum, periodDurationUs);
       int newIndexFirstSegmentNum = newIndex.getFirstSegmentNum();
       long newIndexStartTimeUs = newIndex.getTimeUs(newIndexFirstSegmentNum);
       if (oldIndexEndTimeUs == newIndexStartTimeUs) {
         // The new index continues where the old one ended, with no overlap.
-        segmentNumShift += oldIndex.getLastSegmentNum(periodDurationUs) + 1
+        segmentNumShift += oldIndexLastSegmentNum + 1 - newIndexFirstSegmentNum;
-            - newIndexFirstSegmentNum;
       } else if (oldIndexEndTimeUs < newIndexStartTimeUs) {
         // There's a gap between the old index and the new one which means we've slipped behind the
         // live window and can't proceed.
@@ -429,12 +445,8 @@ public class DefaultDashChunkSource implements DashChunkSource {
       return segmentIndex.getFirstSegmentNum() + segmentNumShift;
     }
 
-    public int getLastSegmentNum() {
+    public int getSegmentCount() {
-      int lastSegmentNum = segmentIndex.getLastSegmentNum(periodDurationUs);
+      return segmentIndex.getSegmentCount(periodDurationUs);
-      if (lastSegmentNum == DashSegmentIndex.INDEX_UNBOUNDED) {
-        return DashSegmentIndex.INDEX_UNBOUNDED;
-      }
-      return lastSegmentNum + segmentNumShift;
     }
 
     public long getSegmentStartTimeUs(int segmentNum) {

library/src/main/java/com/google/android/exoplayer2/source/dash/manifest/Representation.java

@@ -318,8 +318,8 @@ public abstract class Representation {
     }
 
     @Override
-    public int getLastSegmentNum(long periodDurationUs) {
+    public int getSegmentCount(long periodDurationUs) {
-      return segmentBase.getLastSegmentNum(periodDurationUs);
+      return segmentBase.getSegmentCount(periodDurationUs);
     }
 
     @Override

library/src/main/java/com/google/android/exoplayer2/source/dash/manifest/SegmentBase.java

@@ -130,18 +130,22 @@ public abstract class SegmentBase {
      */
     public int getSegmentNum(long timeUs, long periodDurationUs) {
       final int firstSegmentNum = getFirstSegmentNum();
-      int lowIndex = firstSegmentNum;
+      final int segmentCount = getSegmentCount(periodDurationUs);
-      int highIndex = getLastSegmentNum(periodDurationUs);
+      if (segmentCount == 0) {
+        return firstSegmentNum;
+      }
       if (segmentTimeline == null) {
         // All segments are of equal duration (with the possible exception of the last one).
         long durationUs = (duration * C.MICROS_PER_SECOND) / timescale;
         int segmentNum = startNumber + (int) (timeUs / durationUs);
         // Ensure we stay within bounds.
-        return segmentNum < lowIndex ? lowIndex
+        return segmentNum < firstSegmentNum ? firstSegmentNum
-            : highIndex != DashSegmentIndex.INDEX_UNBOUNDED && segmentNum > highIndex ? highIndex
+            : segmentCount == DashSegmentIndex.INDEX_UNBOUNDED ? segmentNum
-            : segmentNum;
+            : Math.min(segmentNum, firstSegmentNum + segmentCount - 1);
       } else {
-        // The high index cannot be unbounded. Identify the segment using binary search.
+        // The index cannot be unbounded. Identify the segment using binary search.
+        int lowIndex = firstSegmentNum;
+        int highIndex = firstSegmentNum + segmentCount - 1;
         while (lowIndex <= highIndex) {
           int midIndex = lowIndex + (highIndex - lowIndex) / 2;
           long midTimeUs = getSegmentTimeUs(midIndex);
@@ -165,7 +169,9 @@ public abstract class SegmentBase {
         long duration = segmentTimeline.get(sequenceNumber - startNumber).duration;
         return (duration * C.MICROS_PER_SECOND) / timescale;
       } else {
-        return sequenceNumber == getLastSegmentNum(periodDurationUs)
+        int segmentCount = getSegmentCount(periodDurationUs);
+        return segmentCount != DashSegmentIndex.INDEX_UNBOUNDED
+            && sequenceNumber == (getFirstSegmentNum() + segmentCount - 1)
             ? (periodDurationUs - getSegmentTimeUs(sequenceNumber))
             : ((duration * C.MICROS_PER_SECOND) / timescale);
       }
@@ -201,9 +207,9 @@ public abstract class SegmentBase {
     }
 
     /**
-     * @see DashSegmentIndex#getLastSegmentNum(long)
+     * @see DashSegmentIndex#getSegmentCount(long)
      */
-    public abstract int getLastSegmentNum(long periodDurationUs);
+    public abstract int getSegmentCount(long periodDurationUs);
 
     /**
      * @see DashSegmentIndex#isExplicit()
@@ -250,8 +256,8 @@ public abstract class SegmentBase {
     }
 
     @Override
-    public int getLastSegmentNum(long periodDurationUs) {
+    public int getSegmentCount(long periodDurationUs) {
-      return startNumber + mediaSegments.size() - 1;
+      return mediaSegments.size();
     }
 
     @Override
@@ -322,14 +328,14 @@ public abstract class SegmentBase {
     }
 
     @Override
-    public int getLastSegmentNum(long periodDurationUs) {
+    public int getSegmentCount(long periodDurationUs) {
       if (segmentTimeline != null) {
-        return segmentTimeline.size() + startNumber - 1;
+        return segmentTimeline.size();
-      } else if (periodDurationUs == C.TIME_UNSET) {
+      } else if (periodDurationUs != C.TIME_UNSET) {
-        return DashSegmentIndex.INDEX_UNBOUNDED;
-      } else {
         long durationUs = (duration * C.MICROS_PER_SECOND) / timescale;
-        return startNumber + (int) Util.ceilDivide(periodDurationUs, durationUs) - 1;
+        return (int) Util.ceilDivide(periodDurationUs, durationUs);
+      } else {
+        return DashSegmentIndex.INDEX_UNBOUNDED;
       }
     }
 

library/src/main/java/com/google/android/exoplayer2/source/dash/manifest/SingleSegmentIndex.java

@@ -57,8 +57,8 @@ import com.google.android.exoplayer2.source.dash.DashSegmentIndex;
   }
 
   @Override
-  public int getLastSegmentNum(long periodDurationUs) {
+  public int getSegmentCount(long periodDurationUs) {
-    return 0;
+    return 1;
   }
 
   @Override