Fix FMP4 playback duration and absent tfdt handling.

- Parse duration from mehd box for FMP4.
- Handle absent tfdt boxes by accumulating decode time
  from one fragment to the next.

Issue: #1529
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=122512416

library/src/main/java/com/google/android/exoplayer/extractor/mp4/Atom.java

@@ -82,6 +82,7 @@ import java.util.List;
   public static final int TYPE_moof = Util.getIntegerCodeForString("moof");
   public static final int TYPE_traf = Util.getIntegerCodeForString("traf");
   public static final int TYPE_mvex = Util.getIntegerCodeForString("mvex");
+  public static final int TYPE_mehd = Util.getIntegerCodeForString("mehd");
   public static final int TYPE_tkhd = Util.getIntegerCodeForString("tkhd");
   public static final int TYPE_edts = Util.getIntegerCodeForString("edts");
   public static final int TYPE_elst = Util.getIntegerCodeForString("elst");

library/src/main/java/com/google/android/exoplayer/extractor/mp4/AtomParsers.java

@@ -50,11 +50,13 @@ import java.util.List;
    *
    * @param trak Atom to parse.
    * @param mvhd Movie header atom, used to get the timescale.
+   * @param duration The duration in units of the timescale declared in the mvhd atom, or -1 if the
+   *     duration should be parsed from the tkhd atom.
    * @param drmInitData {@link DrmInitData} to be included in the format.
    * @param isQuickTime True for QuickTime media. False otherwise.
    * @return A {@link Track} instance, or {@code null} if the track's type isn't supported.
    */
-  public static Track parseTrak(Atom.ContainerAtom trak, Atom.LeafAtom mvhd,
+  public static Track parseTrak(Atom.ContainerAtom trak, Atom.LeafAtom mvhd, long duration,
       DrmInitData drmInitData, boolean isQuickTime) {
     Atom.ContainerAtom mdia = trak.getContainerAtomOfType(Atom.TYPE_mdia);
     int trackType = parseHdlr(mdia.getLeafAtomOfType(Atom.TYPE_hdlr).data);
@@ -63,7 +65,9 @@ import java.util.List;
     }
 
     TkhdData tkhdData = parseTkhd(trak.getLeafAtomOfType(Atom.TYPE_tkhd).data);
-    long duration = tkhdData.duration;
+    if (duration == -1) {
+      duration = tkhdData.duration;
+    }
     long movieTimescale = parseMvhd(mvhd.data);
     long durationUs;
     if (duration == -1) {
@@ -490,6 +494,11 @@ import java.util.List;
       duration = -1;
     } else {
       duration = version == 0 ? tkhd.readUnsignedInt() : tkhd.readUnsignedLongToLong();
+      if (duration == 0) {
+        // 0 duration normally indicates that the file is fully fragmented (i.e. all of the media
+        // samples are in fragments). Treat as unknown.
+        duration = -1;
+      }
     }
 
     tkhd.skipBytes(16);

library/src/main/java/com/google/android/exoplayer/extractor/mp4/FragmentedMp4Extractor.java

@@ -166,6 +166,10 @@ public final class FragmentedMp4Extractor implements Extractor {
 
   @Override
   public void seek() {
+    int trackCount = trackBundles.size();
+    for (int i = 0; i < trackCount; i++) {
+      trackBundles.valueAt(i).reset();
+    }
     containerAtoms.clear();
     enterReadingAtomHeaderState();
   }
@@ -340,12 +344,15 @@ public final class FragmentedMp4Extractor implements Extractor {
     // Read declaration of track fragments in the Moov box.
     ContainerAtom mvex = moov.getContainerAtomOfType(Atom.TYPE_mvex);
     SparseArray<DefaultSampleValues> defaultSampleValuesArray = new SparseArray<>();
+    long duration = -1;
     int mvexChildrenSize = mvex.leafChildren.size();
     for (int i = 0; i < mvexChildrenSize; i++) {
       Atom.LeafAtom atom = mvex.leafChildren.get(i);
       if (atom.type == Atom.TYPE_trex) {
         Pair<Integer, DefaultSampleValues> trexData = parseTrex(atom.data);
         defaultSampleValuesArray.put(trexData.first, trexData.second);
+      } else if (atom.type == Atom.TYPE_mehd) {
+        duration = parseMehd(atom.data);
       }
     }
 
@@ -355,7 +362,7 @@ public final class FragmentedMp4Extractor implements Extractor {
     for (int i = 0; i < moovContainerChildrenSize; i++) {
       Atom.ContainerAtom atom = moov.containerChildren.get(i);
       if (atom.type == Atom.TYPE_trak) {
-        Track track = AtomParsers.parseTrak(atom, moov.getLeafAtomOfType(Atom.TYPE_mvhd),
+        Track track = AtomParsers.parseTrak(atom, moov.getLeafAtomOfType(Atom.TYPE_mvhd), duration,
             drmInitData, false);
         if (track != null) {
           tracks.put(track.id, track);
@@ -402,6 +409,16 @@ public final class FragmentedMp4Extractor implements Extractor {
         defaultSampleDuration, defaultSampleSize, defaultSampleFlags));
   }
 
+  /**
+   * Parses an mehd atom (defined in 14496-12).
+   */
+  private static long parseMehd(ParsableByteArray mehd) {
+    mehd.setPosition(Atom.HEADER_SIZE);
+    int fullAtom = mehd.readInt();
+    int version = Atom.parseFullAtomVersion(fullAtom);
+    return version == 0 ? mehd.readUnsignedInt() : mehd.readUnsignedLongToLong();
+  }
+
   private static void parseMoof(ContainerAtom moof, SparseArray<TrackBundle> trackBundleArray,
       int flags, byte[] extendedTypeScratch) throws ParserException {
     int moofContainerChildrenSize = moof.containerChildren.size();
@@ -427,15 +444,13 @@ public final class FragmentedMp4Extractor implements Extractor {
     if (trackBundle == null) {
       return;
     }
+
     TrackFragment fragment = trackBundle.fragment;
-    trackBundle.currentSampleIndex = 0;
-    fragment.reset();
+    long decodeTime = fragment.nextFragmentDecodeTime;
+    trackBundle.reset();
 
     LeafAtom tfdtAtom = traf.getLeafAtomOfType(Atom.TYPE_tfdt);
-    long decodeTime;
-    if (tfdtAtom == null || (flags & FLAG_WORKAROUND_IGNORE_TFDT_BOX) != 0) {
-      decodeTime = 0;
-    } else {
+    if (tfdtAtom != null && (flags & FLAG_WORKAROUND_IGNORE_TFDT_BOX) == 0) {
       decodeTime = parseTfdt(traf.getLeafAtomOfType(Atom.TYPE_tfdt).data);
     }
 
@@ -661,6 +676,7 @@ public final class FragmentedMp4Extractor implements Extractor {
           && (!workaroundEveryVideoFrameIsSyncFrame || i == 0);
       cumulativeTime += sampleDuration;
     }
+    fragment.nextFragmentDecodeTime = cumulativeTime;
   }
 
   private static void parseUuid(ParsableByteArray uuid, TrackFragment out,
@@ -961,7 +977,7 @@ public final class FragmentedMp4Extractor implements Extractor {
         || atom == Atom.TYPE_tfhd || atom == Atom.TYPE_tkhd || atom == Atom.TYPE_trex
         || atom == Atom.TYPE_trun || atom == Atom.TYPE_pssh || atom == Atom.TYPE_saiz
         || atom == Atom.TYPE_saio || atom == Atom.TYPE_senc || atom == Atom.TYPE_uuid
-        || atom == Atom.TYPE_elst;
+        || atom == Atom.TYPE_elst || atom == Atom.TYPE_mehd;
   }
 
   /** Returns whether the extractor should parse a container atom with type {@code atom}. */
@@ -992,6 +1008,10 @@ public final class FragmentedMp4Extractor implements Extractor {
       this.track = Assertions.checkNotNull(track);
       this.defaultSampleValues = Assertions.checkNotNull(defaultSampleValues);
       output.format(track.format);
+      reset();
+    }
+
+    public void reset() {
       fragment.reset();
       currentSampleIndex = 0;
     }

library/src/main/java/com/google/android/exoplayer/extractor/mp4/Mp4Extractor.java

@@ -310,7 +310,7 @@ public final class Mp4Extractor implements Extractor, SeekMap {
         continue;
       }
 
-      Track track = AtomParsers.parseTrak(atom, moov.getLeafAtomOfType(Atom.TYPE_mvhd), null,
+      Track track = AtomParsers.parseTrak(atom, moov.getLeafAtomOfType(Atom.TYPE_mvhd), -1, null,
           isQuickTime);
       if (track == null) {
         continue;

library/src/main/java/com/google/android/exoplayer/extractor/mp4/TrackFragment.java

@@ -80,15 +80,20 @@ import java.io.IOException;
    * Whether {@link #sampleEncryptionData} needs populating with the actual encryption data.
    */
   public boolean sampleEncryptionDataNeedsFill;
+  /**
+   * The absolute decode time of the start of the next fragment.
+   */
+  public long nextFragmentDecodeTime;
 
   /**
    * Resets the fragment.
    * <p>
-   * The {@link #length} is set to 0, and both {@link #definesEncryptionData} and
-   * {@link #sampleEncryptionDataNeedsFill} is set to false.
+   * {@link #length} and {@link #nextFragmentDecodeTime} are set to 0, and both
+   * {@link #definesEncryptionData} and {@link #sampleEncryptionDataNeedsFill} is set to false.
    */
   public void reset() {
     length = 0;
+    nextFragmentDecodeTime = 0;
     definesEncryptionData = false;
     sampleEncryptionDataNeedsFill = false;
   }