Handle non-indexed representations.

These may occur in VOD streams where a representation's data
is small enough not to require segmentation or an index. For
example subtitle files.

Issue: #268

library/src/main/java/com/google/android/exoplayer/dash/DashChunkSource.java

@@ -451,7 +451,7 @@ public class DashChunkSource implements ChunkSource {
     DataSpec dataSpec = new DataSpec(segmentUri.getUri(), segmentUri.start, segmentUri.length,
         representation.getCacheKey());
 
-    long presentationTimeOffsetUs = representation.presentationTimeOffsetMs * 1000;
+    long presentationTimeOffsetUs = representation.presentationTimeOffsetUs;
     if (representation.format.mimeType.equals(MimeTypes.TEXT_VTT)) {
       if (representationHolder.vttHeaderOffsetUs != presentationTimeOffsetUs) {
         // Update the VTT header.

library/src/main/java/com/google/android/exoplayer/dash/DashSingleSegmentIndex.java

@@ -0,0 +1,60 @@
+package com.google.android.exoplayer.dash;
+
+import com.google.android.exoplayer.dash.mpd.RangedUri;
+
+/**
+ * A {@link DashSegmentIndex} that defines a single segment.
+ */
+public class DashSingleSegmentIndex implements DashSegmentIndex {
+
+  private final long startTimeUs;
+  private final long durationUs;
+  private final RangedUri uri;
+
+  /**
+   * @param startTimeUs The start time of the segment, in microseconds.
+   * @param durationUs The duration of the segment, in microseconds.
+   * @param uri A {@link RangedUri} defining the location of the segment data.
+   */
+  public DashSingleSegmentIndex(long startTimeUs, long durationUs, RangedUri uri) {
+    this.startTimeUs = startTimeUs;
+    this.durationUs = durationUs;
+    this.uri = uri;
+  }
+
+  @Override
+  public int getSegmentNum(long timeUs) {
+    return 0;
+  }
+
+  @Override
+  public long getTimeUs(int segmentNum) {
+    return startTimeUs;
+  }
+
+  @Override
+  public long getDurationUs(int segmentNum) {
+    return durationUs;
+  }
+
+  @Override
+  public RangedUri getSegmentUrl(int segmentNum) {
+    return uri;
+  }
+
+  @Override
+  public int getFirstSegmentNum() {
+    return 0;
+  }
+
+  @Override
+  public int getLastSegmentNum() {
+    return 0;
+  }
+
+  @Override
+  public boolean isExplicit() {
+    return true;
+  }
+
+}

library/src/main/java/com/google/android/exoplayer/dash/mpd/MediaPresentationDescriptionParser.java

@@ -305,7 +305,7 @@ public class MediaPresentationDescriptionParser extends DefaultHandler
     Format format = buildFormat(id, mimeType, width, height, numChannels, audioSamplingRate,
         bandwidth, language, codecs);
     return buildRepresentation(periodStartMs, periodDurationMs, contentId, -1, format,
-        segmentBase);
+        segmentBase != null ? segmentBase : new SingleSegmentBase(baseUrl));
   }
 
   protected Format buildFormat(String id, String mimeType, int width, int height, int numChannels,

library/src/main/java/com/google/android/exoplayer/dash/mpd/Representation.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer.dash.mpd;
 
 import com.google.android.exoplayer.chunk.Format;
 import com.google.android.exoplayer.dash.DashSegmentIndex;
+import com.google.android.exoplayer.dash.DashSingleSegmentIndex;
 import com.google.android.exoplayer.dash.mpd.SegmentBase.MultiSegmentBase;
 import com.google.android.exoplayer.dash.mpd.SegmentBase.SingleSegmentBase;
 
@@ -63,7 +64,7 @@ public abstract class Representation {
   /**
    * The offset of the presentation timestamps in the media stream relative to media time.
    */
-  public final long presentationTimeOffsetMs;
+  public final long presentationTimeOffsetUs;
 
   private final RangedUri initializationUri;
 
@@ -101,7 +102,7 @@ public abstract class Representation {
     this.revisionId = revisionId;
     this.format = format;
     initializationUri = segmentBase.getInitialization(this);
-    presentationTimeOffsetMs = (segmentBase.presentationTimeOffset * 1000) / segmentBase.timescale;
+    presentationTimeOffsetUs = segmentBase.getPresentationTimeOffsetUs();
   }
 
   /**
@@ -156,6 +157,7 @@ public abstract class Representation {
     public final long contentLength;
 
     private final RangedUri indexUri;
+    private final DashSingleSegmentIndex segmentIndex;
 
     /**
      * @param periodStartMs The start time of the enclosing period in milliseconds.
@@ -198,6 +200,10 @@ public abstract class Representation {
       this.uri = segmentBase.uri;
       this.indexUri = segmentBase.getIndex();
       this.contentLength = contentLength;
+      // If we have an index uri then the index is defined externally, and we shouldn't return one
+      // directly. If we don't, then we can't do better than an index defining a single segment.
+      segmentIndex = indexUri != null ? null : new DashSingleSegmentIndex(periodStartMs * 1000,
+          periodDurationMs * 1000, new RangedUri(uri, null, 0, -1));
     }
 
     @Override
@@ -207,7 +213,7 @@ public abstract class Representation {
 
     @Override
     public DashSegmentIndex getIndex() {
-      return null;
+      return segmentIndex;
     }
 
   }

library/src/main/java/com/google/android/exoplayer/dash/mpd/SegmentBase.java

@@ -56,6 +56,15 @@ public abstract class SegmentBase {
     return initialization;
   }
 
+  /**
+   * Gets the presentation time offset, in microseconds.
+   *
+   * @return The presentation time offset, in microseconds.
+   */
+  public long getPresentationTimeOffsetUs() {
+    return Util.scaleLargeTimestamp(presentationTimeOffset, C.MICROS_PER_SECOND, timescale);
+  }
+
   /**
    * A {@link SegmentBase} that defines a single segment.
    */
@@ -87,8 +96,15 @@ public abstract class SegmentBase {
       this.indexLength = indexLength;
     }
 
+    /**
+     * @param uri The uri of the segment.
+     */
+    public SingleSegmentBase(Uri uri) {
+      this(null, 1, 0, uri, 0, -1);
+    }
+
     public RangedUri getIndex() {
-      return new RangedUri(uri, null, indexStart, indexLength);
+      return indexLength <= 0 ? null : new RangedUri(uri, null, indexStart, indexLength);
     }
 
   }