Fix frame timecode overflow (#5)

* Add "target" to gitignore.

* fix: Fix case where frames might be added out of order

For example, if an entire track is added starting at timecode 0,
and then another track is added starting against at timecode 0.

.gitignore

@@ -4,3 +4,4 @@ build/
 .classpath
 .settings/
 .project
+target

src/main/java/org/ebml/matroska/MatroskaCluster.java

@@ -44,7 +44,7 @@ class MatroskaCluster
   private final List<Long> sliencedTracks = new ArrayList<>();
 
   private long clusterTimecode = Long.MAX_VALUE;
-  private long lastTimecode = 0;
+  private long maxFrameTimecode = 0;
   private long durationLimit = 500;
 
   public MatroskaCluster()
@@ -69,14 +69,19 @@ public void addFrame(final MatroskaFileFrame frame)
     {
       clusterTimecode = frame.getTimecode();
     }
-    lastTimecode = frame.getTimecode();
+    maxFrameTimecode = Math.max(maxFrameTimecode, frame.getTimecode());
     frames.add(frame);
     tracks.add(frame.getTrackNo());
   }
 
-  public boolean isFlushNeeded()
+  public boolean isFlushNeeded(long nextFrameTimecode)
   {
-    return (lastTimecode - clusterTimecode) > durationLimit;
+    return
+            // The next frame will exceed the duration limit
+            (nextFrameTimecode - clusterTimecode) > durationLimit ||
+            // The next frame is older, and would lower the cluster timecode enough to overflow the frame timecode
+            // for one of the existing frames.
+                    maxFrameTimecode - nextFrameTimecode > Short.MAX_VALUE;
   }
 
   public long flush(final DataWriter ioDW)
@@ -136,6 +141,7 @@ public long flush(final DataWriter ioDW)
       frames.clear();
       tracks.clear();
       clusterTimecode = Long.MAX_VALUE;
+      maxFrameTimecode = Long.MIN_VALUE;
     }
   }
 

src/main/java/org/ebml/matroska/MatroskaFileWriter.java

@@ -237,7 +237,7 @@ public void unsilenceTrack(final long trackNumber)
   public void addFrame(final MatroskaFileFrame frame)
   {
     initialize();
-    if ((onlyAudioTracks && cluster.isFlushNeeded())
+    if ((onlyAudioTracks && cluster.isFlushNeeded(frame.getTimecode()))
         || (frame.isKeyFrame() && videoTrackNumbers.contains(frame.getTrackNo())))
     {
       flush();