isomp4: add DASH tfdt box support

MPEG DASH has defined a set of new boxes to specify duration, indexes and
offsets of ISOBMFF fragments.

The Track Fragment Base Media Decode Time (tfdt) Box can in particular be
included inside a traf box to specify the absolute decode time, measured on the
media timeline, of the first sample in decode order in the track fragment.

This information can be used by the isomp4 demux to find out the current position of
an MP4 fragment in the timeline.

This patch adds code to isomp4 to:
- parse the tfdt box
- adjust the time/position member of the new segment sent when playback starts

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=677535

gst/isomp4/qtdemux.c

@@ -2372,12 +2372,44 @@ unknown_stream:
   }
 }
 
+static gboolean
+qtdemux_parse_tfdt (GstQTDemux * qtdemux, GstByteReader * br,
+    guint64 * decode_time)
+{
+  guint32 version = 0;
+
+  if (!gst_byte_reader_get_uint32_be (br, &version))
+    return FALSE;
+
+  version >>= 24;
+  if (version == 1) {
+    if (!gst_byte_reader_get_uint64_be (br, decode_time))
+      goto failed;
+  } else {
+    guint32 dec_time = 0;
+    if (!gst_byte_reader_get_uint32_be (br, &dec_time))
+      goto failed;
+    *decode_time = dec_time;
+  }
+
+  GST_INFO_OBJECT (qtdemux, "Track fragment decode time: %" G_GUINT64_FORMAT,
+      *decode_time);
+
+  return TRUE;
+
+failed:
+  {
+    GST_DEBUG_OBJECT (qtdemux, "parsing tfdt failed");
+    return FALSE;
+  }
+}
+
 static gboolean
 qtdemux_parse_moof (GstQTDemux * qtdemux, const guint8 * buffer, guint length,
     guint64 moof_offset, QtDemuxStream * stream)
 {
-  GNode *moof_node, *traf_node, *tfhd_node, *trun_node;
-  GstByteReader trun_data, tfhd_data;
+  GNode *moof_node, *traf_node, *tfhd_node, *trun_node, *tfdt_node;
+  GstByteReader trun_data, tfhd_data, tfdt_data;
   guint32 ds_size = 0, ds_duration = 0, ds_flags = 0;
   gint64 base_offset, running_offset;
 
@@ -2400,6 +2432,22 @@ qtdemux_parse_moof (GstQTDemux * qtdemux, const guint8 * buffer, guint length,
     if (!qtdemux_parse_tfhd (qtdemux, &tfhd_data, &stream, &ds_duration,
             &ds_size, &ds_flags, &base_offset))
       goto missing_tfhd;
+    tfdt_node =
+        qtdemux_tree_get_child_by_type_full (traf_node, FOURCC_tfdt,
+        &tfdt_data);
+    if (tfdt_node) {
+      guint64 decode_time = 0;
+      qtdemux_parse_tfdt (qtdemux, &tfdt_data, &decode_time);
+      /* If there is a new segment pending, update the time/position */
+      if (qtdemux->pending_newsegment) {
+        gst_event_replace (&qtdemux->pending_newsegment,
+            gst_event_new_new_segment (FALSE, 1.0, GST_FORMAT_TIME,
+                0, GST_CLOCK_TIME_NONE,
+                gst_util_uint64_scale (decode_time,
+                    GST_SECOND, stream->timescale)));
+      }
+    }
+
     if (G_UNLIKELY (!stream)) {
       /* we lost track of offset, we'll need to regain it,
        * but can delay complaining until later or avoid doing so altogether */

gst/isomp4/qtdemux_dump.c

@@ -720,6 +720,28 @@ qtdemux_dump_mehd (GstQTDemux * qtdemux, GstByteReader * data, int depth)
   return FALSE;
 }
 
+gboolean
+qtdemux_dump_tfdt (GstQTDemux * qtdemux, GstByteReader * data, int depth)
+{
+  guint32 version = 0;
+  guint64 decode_time;
+  guint value_size;
+
+  if (!gst_byte_reader_get_uint32_be (data, &version))
+    return FALSE;
+
+  GST_LOG ("%*s  version/flags: %08x", depth, "", version);
+
+  value_size = ((version >> 24) == 1) ? sizeof (guint64) : sizeof (guint32);
+  if (qt_atom_parser_get_offset (data, value_size, &decode_time)) {
+    GST_LOG ("%*s  Track fragment decode time: %" G_GUINT64_FORMAT,
+        depth, "", decode_time);
+    return TRUE;
+  }
+
+  return FALSE;
+}
+
 gboolean
 qtdemux_dump_sdtp (GstQTDemux * qtdemux, GstByteReader * data, int depth)
 {

gst/isomp4/qtdemux_dump.h

@@ -75,6 +75,8 @@ gboolean qtdemux_dump_mehd (GstQTDemux * qtdemux, GstByteReader * data,
     int depth);
 gboolean qtdemux_dump_sdtp (GstQTDemux * qtdemux, GstByteReader * data,
     int depth);
+gboolean qtdemux_dump_tfdt (GstQTDemux * qtdemux, GstByteReader * data,
+    int depth);
 gboolean qtdemux_dump_unknown (GstQTDemux * qtdemux, GstByteReader * data,
     int depth);
 

gst/isomp4/qtdemux_fourcc.h

@@ -230,6 +230,9 @@ G_BEGIN_DECLS
 #define FOURCC_ovc1     GST_MAKE_FOURCC('o','v','c','1')
 #define FOURCC_owma     GST_MAKE_FOURCC('o','w','m','a')
 
+/* MPEG DASH */
+#define FOURCC_tfdt     GST_MAKE_FOURCC('t','f','d','t')
+
 G_END_DECLS
 
 #endif /* __GST_QTDEMUX_FOURCC_H__ */

gst/isomp4/qtdemux_types.c

@@ -171,6 +171,7 @@ static const QtNodeType qt_node_types[] = {
       qtdemux_dump_mehd},
   {FOURCC_ovc1, "ovc1", 0},
   {FOURCC_owma, "owma", 0},
+  {FOURCC_tfdt, "Track fragment decode time", 0, qtdemux_dump_tfdt},
   {0, "unknown", 0,},
 };