videobox: avoid dropping caps fields for passthrough caps transform

Fixes potential negotiation failure in case downstream element
is a bit picky regarding the fields in question.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2786>

diff --git a/subprojects/gst-plugins-good/gst/videobox/gstvideobox.c b/subprojects/gst-plugins-good/gst/videobox/gstvideobox.c
index 9c69e49..302e714 100644 (file)
--- a/subprojects/gst-plugins-good/gst/videobox/gstvideobox.c
+++ b/subprojects/gst-plugins-good/gst/videobox/gstvideobox.c
@@ -2949,11 +2949,13 @@ gst_video_box_transform_caps (GstBaseTransform * trans,
       gst_structure_set_value (structure, "format", &val);
       g_value_unset (&val);
       g_value_unset (&list);
-    }
-
-    gst_structure_remove_field (structure, "colorimetry");
-    gst_structure_remove_field (structure, "chroma-site");
 
+      /* format list above makes for non-fixed caps;
+       * so basetransform and peers will be enlisted to decide these parts,
+       * otherwise leave as-is for passthrough case */
+      gst_structure_remove_field (structure, "colorimetry");
+      gst_structure_remove_field (structure, "chroma-site");
+    }
     gst_caps_append_structure (to, structure);
   }