Support signalling of last segment number via supplemental descriptor in mpd

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

@@ -42,6 +42,7 @@ import com.google.android.exoplayer2.source.chunk.SingleSampleMediaChunk;
 import com.google.android.exoplayer2.source.dash.PlayerEmsgHandler.PlayerTrackEmsgHandler;
 import com.google.android.exoplayer2.source.dash.manifest.AdaptationSet;
 import com.google.android.exoplayer2.source.dash.manifest.DashManifest;
+import com.google.android.exoplayer2.source.dash.manifest.Descriptor;
 import com.google.android.exoplayer2.source.dash.manifest.RangedUri;
 import com.google.android.exoplayer2.source.dash.manifest.Representation;
 import com.google.android.exoplayer2.trackselection.TrackSelection;
@@ -325,10 +326,34 @@ public class DefaultDashChunkSource implements DashChunkSource {
       return;
     }
 
+    List<Descriptor> listDescriptors;
+    Integer lastSegmentNumberSchemeIdUri = Integer.MAX_VALUE;
+    String sampleMimeType = trackSelection.getFormat(periodIndex).sampleMimeType;
+
+    if (sampleMimeType.contains("video") || sampleMimeType.contains("audio")) {
+
+      int track_type = sampleMimeType.contains("video")? C.TRACK_TYPE_VIDEO : C.TRACK_TYPE_AUDIO;
+
+      if (!manifest.getPeriod(periodIndex).adaptationSets.get(manifest.getPeriod(periodIndex)
+          .getAdaptationSetIndex(track_type)).supplementalProperties.isEmpty()) {
+        listDescriptors = manifest.getPeriod(periodIndex).adaptationSets
+            .get(manifest.getPeriod(periodIndex).getAdaptationSetIndex(track_type))
+            .supplementalProperties;
+        for ( Descriptor descriptor: listDescriptors ) {
+          if (descriptor.schemeIdUri.equalsIgnoreCase
+              ("http://dashif.org/guidelines/last-segment-number")) {
+            lastSegmentNumberSchemeIdUri = Integer.valueOf(descriptor.value);
+          }
+        }
+      }
+    }
+
     long firstAvailableSegmentNum =
         representationHolder.getFirstAvailableSegmentNum(manifest, periodIndex, nowUnixTimeUs);
     long lastAvailableSegmentNum =
-        representationHolder.getLastAvailableSegmentNum(manifest, periodIndex, nowUnixTimeUs);
+        Math.min(representationHolder.
+                getLastAvailableSegmentNum(manifest, periodIndex, nowUnixTimeUs),
+                lastSegmentNumberSchemeIdUri);
 
     updateLiveEdgeTimeUs(representationHolder, lastAvailableSegmentNum);