qtdemux: Add reference timestamp meta with UTC times based on the ONVIF Export File Format CorrectStartTime box to outgoing buffers

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2525>

subprojects/gst-plugins-good/gst/isomp4/fourcc.h

@@ -420,6 +420,9 @@ G_BEGIN_DECLS
 
 #define FOURCC_metx     GST_MAKE_FOURCC('m','e','t','x')
 
+/* ONVIF Export File Format */
+#define FOURCC_cstb     GST_MAKE_FOURCC('c','s','t','b')
+
 G_END_DECLS
 
 #endif /* __FOURCC_H__ */

subprojects/gst-plugins-good/gst/isomp4/qtdemux.c

@@ -2067,6 +2067,7 @@ gst_qtdemux_reset (GstQTDemux * qtdemux, gboolean hard)
     gst_caps_replace (&qtdemux->media_caps, NULL);
     qtdemux->timescale = 0;
     qtdemux->got_moov = FALSE;
+    qtdemux->start_utc_time = GST_CLOCK_TIME_NONE;
     qtdemux->cenc_aux_info_offset = 0;
     qtdemux->cenc_aux_info_sizes = NULL;
     qtdemux->cenc_aux_sample_count = 0;
@@ -3054,6 +3055,57 @@ qtdemux_parse_sidx (GstQTDemux * qtdemux, const guint8 * buffer, gint length)
   gst_isoff_qt_sidx_parser_clear (&sidx_parser);
 }
 
+static void
+qtdemux_parse_cstb (GstQTDemux * qtdemux, GstByteReader * data)
+{
+  guint64 start_time;
+  guint32 entry_count;
+
+  GST_DEBUG_OBJECT (qtdemux, "Parsing CorrectStartTime box");
+
+  qtdemux->start_utc_time = GST_CLOCK_TIME_NONE;
+
+  if (gst_byte_reader_get_remaining (data) < 4) {
+    GST_WARNING_OBJECT (qtdemux, "Too small CorrectStartTime box");
+    return;
+  }
+
+  entry_count = gst_byte_reader_get_uint32_be_unchecked (data);
+  if (entry_count == 0)
+    return;
+
+  /* XXX: We assume that all start times are the same as different start times
+   * would violate the MP4 synchronization model, so we just take the first
+   * one here and apply it to all tracks.
+   */
+
+  if (gst_byte_reader_get_remaining (data) < entry_count * 12) {
+    GST_WARNING_OBJECT (qtdemux, "Too small CorrectStartTime box");
+    return;
+  }
+
+  /* Skip track id */
+  gst_byte_reader_skip_unchecked (data, 4);
+
+  /* In 100ns intervals */
+  start_time = gst_byte_reader_get_uint64_be_unchecked (data);
+
+  /* Convert from Jan 1 1601 to Jan 1 1970 */
+  if (start_time < 11644473600 * G_GUINT64_CONSTANT (10000000)) {
+    GST_WARNING_OBJECT (qtdemux, "Start UTC time before UNIX epoch");
+    return;
+  }
+  start_time -= 11644473600 * G_GUINT64_CONSTANT (10000000);
+
+  /* Convert to GstClockTime */
+  start_time *= 100;
+
+  GST_DEBUG_OBJECT (qtdemux, "Start UTC time: %" GST_TIME_FORMAT,
+      GST_TIME_ARGS (start_time));
+
+  qtdemux->start_utc_time = start_time;
+}
+
 /* caller verifies at least 8 bytes in buf */
 static void
 extract_initial_length_and_fourcc (const guint8 * data, guint size,
@@ -4701,6 +4753,34 @@ gst_qtdemux_loop_state_header (GstQTDemux * qtdemux)
       gst_buffer_unref (sidx);
       break;
     }
+    case FOURCC_meta:
+    {
+      GstBuffer *meta = NULL;
+      GNode *node, *child;
+      GstByteReader child_data;
+      ret = gst_qtdemux_pull_atom (qtdemux, cur_offset, length, &meta);
+      if (ret != GST_FLOW_OK)
+        goto beach;
+      qtdemux->offset += length;
+      gst_buffer_map (meta, &map, GST_MAP_READ);
+
+      node = g_node_new (map.data);
+
+      qtdemux_parse_node (qtdemux, node, map.data, map.size);
+
+      /* Parse ONVIF Export File Format CorrectStartTime box if available */
+      if ((child =
+              qtdemux_tree_get_child_by_type_full (node, FOURCC_cstb,
+                  &child_data))) {
+        qtdemux_parse_cstb (qtdemux, &child_data);
+      }
+
+      g_node_destroy (node);
+
+      gst_buffer_unmap (meta, &map);
+      gst_buffer_unref (meta);
+      break;
+    }
     default:
     {
       GstBuffer *unknown = NULL;
@@ -6210,6 +6290,15 @@ gst_qtdemux_decorate_and_push_buffer (GstQTDemux * qtdemux,
   /* we're going to modify the metadata */
   buf = gst_buffer_make_writable (buf);
 
+  if (qtdemux->start_utc_time != GST_CLOCK_TIME_NONE) {
+    static GstStaticCaps unix_caps = GST_STATIC_CAPS ("timestamp/x-unix");
+    GstCaps *caps = gst_static_caps_get (&unix_caps);
+    gst_buffer_add_reference_timestamp_meta (buf, caps,
+        pts + qtdemux->start_utc_time - stream->cslg_shift,
+        GST_CLOCK_TIME_NONE);
+    gst_caps_unref (caps);
+  }
+
   GST_BUFFER_DTS (buf) = dts;
   GST_BUFFER_PTS (buf) = pts;
   GST_BUFFER_DURATION (buf) = duration;
@@ -7353,6 +7442,7 @@ gst_qtdemux_process_adapter (GstQTDemux * demux, gboolean force)
               if (demux->moov_node)
                 g_node_destroy (demux->moov_node);
               demux->moov_node = NULL;
+              demux->start_utc_time = GST_CLOCK_TIME_NONE;
             }
 
             demux->last_moov_offset = demux->offset;
@@ -7475,6 +7565,21 @@ gst_qtdemux_process_adapter (GstQTDemux * demux, gboolean force)
         } else if (fourcc == FOURCC_sidx) {
           GST_DEBUG_OBJECT (demux, "Parsing [sidx]");
           qtdemux_parse_sidx (demux, data, demux->neededbytes);
+        } else if (fourcc == FOURCC_meta) {
+          GNode *node, *child;
+          GstByteReader child_data;
+
+          node = g_node_new ((gpointer) data);
+          qtdemux_parse_node (demux, node, data, demux->neededbytes);
+
+          /* Parse ONVIF Export File Format CorrectStartTime box if available */
+          if ((child =
+                  qtdemux_tree_get_child_by_type_full (node, FOURCC_cstb,
+                      &child_data))) {
+            qtdemux_parse_cstb (demux, &child_data);
+          }
+
+          g_node_destroy (node);
         } else {
           switch (fourcc) {
             case FOURCC_styp:

subprojects/gst-plugins-good/gst/isomp4/qtdemux.h

@@ -119,6 +119,10 @@ struct _GstQTDemux {
   /* Global duration (in global timescale). Use QTTIME macros to get GstClockTime */
   guint64 duration;
 
+  /* Start UTC time as extracted from the AFIdentification box, reset on every
+   * moov */
+  GstClockTime start_utc_time;
+
   /* Total size of header atoms. Used to calculate fallback overall bitrate */
   guint header_size;
 

subprojects/gst-plugins-good/gst/isomp4/qtdemux_types.c

@@ -232,6 +232,7 @@ static const QtNodeType qt_node_types[] = {
   {FOURCC_adrm, "AAX DRM key data", 0},
   {FOURCC_vttc, "VTTCueBox 14496-30", QT_FLAG_CONTAINER},
   {FOURCC_metx, "XML MetaData Sample Entry", 0},
+  {FOURCC_cstb, "Correct Start Time Box", 0},
   {0, "unknown", 0,},
 };