qtdemux: Cope with difference between QTFF and ISO BMFF specs

The 'meta' atom is defined differently in QTFF and BMFF, so try
to guess which spec the current stream applies to by looking
at the major file type.
diff --git a/gst/isomp4/qtdemux.c b/gst/isomp4/qtdemux.c
index 4fda82a..3ec41b9 100644
--- a/gst/isomp4/qtdemux.c
+++ b/gst/isomp4/qtdemux.c
@@ -7521,7 +7521,13 @@
       case FOURCC_meta:
       {
         GST_DEBUG_OBJECT (qtdemux, "parsing meta atom");
-        qtdemux_parse_container (qtdemux, node, buffer + 12, end);
+        /* You are reading this correctly. QTFF specifies that the
+         * metadata atom is a short atom, whereas ISO BMFF specifies
+         * it's a full atom. joy joy joy */
+        if (qtdemux->major_brand == FOURCC_qt__)
+          qtdemux_parse_container (qtdemux, node, buffer + 8, end);
+        else
+          qtdemux_parse_container (qtdemux, node, buffer + 12, end);
         break;
       }
       case FOURCC_mp4s: