gppmux: enhance ftyp brand heuristic.  Fixes #584360.
diff --git a/gst/quicktime/atoms.h b/gst/quicktime/atoms.h
index 4d8dce1..23bc19b 100644
--- a/gst/quicktime/atoms.h
+++ b/gst/quicktime/atoms.h
@@ -518,6 +518,10 @@
 
   AtomTKHD tkhd;
   AtomMDIA mdia;
+
+  /* some helper info for structural conformity checks */
+  gboolean is_video;
+  gboolean is_h264;
 } AtomTRAK;
 
 typedef struct _AtomMOOV