interlace: Also handle a missing "interlace-mode" field as progressive

Otherwise caps negotiation will fail in situations that are supposed
to work, like:

  "video/x-raw,framerate=(fraction)60/1" ! interlace field-pattern=0 ! "video/x-raw,framerate=(fraction)30/1"

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2335>

diff --git a/subprojects/gst-plugins-bad/gst/interlace/gstinterlace.c b/subprojects/gst-plugins-bad/gst/interlace/gstinterlace.c
index bf7cbfe..ca22e74 100644 (file)
--- a/subprojects/gst-plugins-bad/gst/interlace/gstinterlace.c
+++ b/subprojects/gst-plugins-bad/gst/interlace/gstinterlace.c
@@ -775,7 +775,8 @@ gst_interlace_caps_double_framerate (GstCaps * caps, gboolean half,
     interlace_mode = gst_structure_get_string (s, "interlace-mode");
     /* Do not double the framerate for interlaced - we will either passthrough
      * or fail to negotiate */
-    if (skip_progressive && (g_strcmp0 (interlace_mode, "progressive") != 0))
+    if (skip_progressive && (interlace_mode
+            && g_strcmp0 (interlace_mode, "progressive") != 0))
       continue;
 
     if (G_VALUE_TYPE (val) == GST_TYPE_FRACTION) {