qtdemux: Extract CEA608 framerate from the (first) video stream

EA608 closed caption tracks are a bit special in that each sample
can contain CCs for multiple frames, and CCs can be omitted and have to
be inferred from the duration of the sample then.

As such we take the framerate from the (first) video track here for
CEA608 as there must be one CC byte pair for every video frame
according to the spec.

For CEA708 all is fine and there is one sample per frame.

diff --git a/gst/isomp4/qtdemux.c b/gst/isomp4/qtdemux.c
index 2db46d6..95e27fd 100644 (file)
--- a/gst/isomp4/qtdemux.c
+++ b/gst/isomp4/qtdemux.c
@@ -8518,19 +8518,53 @@ gst_qtdemux_configure_stream (GstQTDemux * qtdemux, QtDemuxStream * stream)
     }
   }
 
-  else if (stream->subtype == FOURCC_clcp) {
-    gboolean fps_available = gst_qtdemux_guess_framerate (qtdemux, stream);
+  else if (stream->subtype == FOURCC_clcp && CUR_STREAM (stream)->caps) {
+    const GstStructure *s;
+    QtDemuxStream *fps_stream = NULL;
+    gboolean fps_available = FALSE;
 
-    if (CUR_STREAM (stream)->caps) {
-      CUR_STREAM (stream)->caps =
-          gst_caps_make_writable (CUR_STREAM (stream)->caps);
+    /* CEA608 closed caption tracks are a bit special in that each sample
+     * can contain CCs for multiple frames, and CCs can be omitted and have to
+     * be inferred from the duration of the sample then.
+     *
+     * As such we take the framerate from the (first) video track here for
+     * CEA608 as there must be one CC byte pair for every video frame
+     * according to the spec.
+     *
+     * For CEA708 all is fine and there is one sample per frame.
+     */
 
-      /* set framerate if calculated framerate is reliable */
-      if (fps_available) {
-        gst_caps_set_simple (CUR_STREAM (stream)->caps,
-            "framerate", GST_TYPE_FRACTION, CUR_STREAM (stream)->fps_n,
-            CUR_STREAM (stream)->fps_d, NULL);
+    s = gst_caps_get_structure (CUR_STREAM (stream)->caps, 0);
+    if (gst_structure_has_name (s, "closedcaption/x-cea-608")) {
+      gint i;
+
+      for (i = 0; i < QTDEMUX_N_STREAMS (qtdemux); i++) {
+        QtDemuxStream *tmp = QTDEMUX_NTH_STREAM (qtdemux, i);
+
+        if (tmp->subtype == FOURCC_vide) {
+          fps_stream = tmp;
+          break;
+        }
       }
+
+      if (fps_stream) {
+        fps_available = gst_qtdemux_guess_framerate (qtdemux, fps_stream);
+        CUR_STREAM (stream)->fps_n = CUR_STREAM (fps_stream)->fps_n;
+        CUR_STREAM (stream)->fps_d = CUR_STREAM (fps_stream)->fps_d;
+      }
+    } else {
+      fps_available = gst_qtdemux_guess_framerate (qtdemux, stream);
+      fps_stream = stream;
+    }
+
+    CUR_STREAM (stream)->caps =
+        gst_caps_make_writable (CUR_STREAM (stream)->caps);
+
+    /* set framerate if calculated framerate is reliable */
+    if (fps_available) {
+      gst_caps_set_simple (CUR_STREAM (stream)->caps,
+          "framerate", GST_TYPE_FRACTION, CUR_STREAM (stream)->fps_n,
+          CUR_STREAM (stream)->fps_d, NULL);
     }
   }