qtmux: Only write 4 byte zero padding to the Video Sample Description in MOV

For MP4 this is not defined, and it actually breaks things for MSE in
Chrome if we do this. For MOV this is required by some broken software
but the official specification says it's optional:
https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html

https://bugzilla.gnome.org/show_bug.cgi?id=777540

diff --git a/gst/isomp4/atoms.c b/gst/isomp4/atoms.c
index ceadb59..101f12d 100644 (file)
--- a/gst/isomp4/atoms.c
+++ b/gst/isomp4/atoms.c
@@ -1544,6 +1544,17 @@ atom_write_size (guint8 ** buffer, guint64 * size, guint64 * offset,
   prop_copy_uint32 (*offset - atom_pos, buffer, size, &atom_pos);
 }
 
+static guint64
+atom_copy_empty (Atom * atom, guint8 ** buffer, guint64 * size,
+    guint64 * offset)
+{
+  guint64 original_offset = *offset;
+
+  prop_copy_uint32 (0, buffer, size, offset);
+
+  return *offset - original_offset;
+}
+
 guint64
 atom_copy_data (Atom * atom, guint8 ** buffer, guint64 * size, guint64 * offset)
 {
@@ -1596,9 +1607,6 @@ atom_info_list_copy_data (GList * ai, guint8 ** buffer, guint64 * size,
     ai = g_list_next (ai);
   }
 
-  /* append 0 as a terminator "length" to work around some broken software */
-  prop_copy_uint32 (0, buffer, size, offset);
-
   return *offset - original_offset;
 }
 
@@ -4135,6 +4143,15 @@ build_tapt_extension (gint clef_width, gint clef_height, gint prof_width,
       atom_data_free);
 }
 
+static AtomInfo *
+build_mov_video_sample_description_padding_extension (void)
+{
+  AtomData *atom_data = atom_data_new (FOURCC_clap);
+
+  return build_atom_info_wrapper ((Atom *) atom_data, atom_copy_empty,
+      atom_data_free);
+}
+
 SampleTableEntryMP4V *
 atom_trak_set_video_type (AtomTRAK * trak, AtomsContext * context,
     VisualSampleEntry * entry, guint32 scale, GList * ext_atoms_list)
@@ -4179,6 +4196,13 @@ atom_trak_set_video_type (AtomTRAK * trak, AtomsContext * context,
   ste->extension_atoms = g_list_append (ste->extension_atoms,
       build_pasp_extension (par_n, par_d));
 
+  if (context->flavor == ATOMS_TREE_FLAVOR_MOV) {
+    /* append 0 as a terminator "length" to work around some broken software */
+    ste->extension_atoms =
+        g_list_append (ste->extension_atoms,
+        build_mov_video_sample_description_padding_extension ());
+  }
+
   return ste;
 }