rawparse: add 'decide_allocation' vfunc to let subclass parse an allocation query

And so send an allocation query. This could be used to check whether
downstream element supports some metas or not.

https://bugzilla.gnome.org/show_bug.cgi?id=760270

2 files changed, 17 insertions, 0 deletions

diff --git a/gst/rawparse/gstrawparse.c b/gst/rawparse/gstrawparse.c
index 3d043fd49..a6468d932 100644
--- a/gst/rawparse/gstrawparse.c
+++ b/gst/rawparse/gstrawparse.c
@@ -222,6 +222,22 @@ gst_raw_parse_set_src_caps (GstRawParse * rp)
   }
 
   rp->negotiated = gst_pad_set_caps (rp->srcpad, caps);
+
+  /* if subclass inplement decide_allocation, send an allocation
+   * query, pass result to subclass and let it handle allocation if needed. */
+  if (rp_class->decide_allocation) {
+    GstQuery *query;
+
+    query = gst_query_new_allocation (caps, TRUE);
+    if (!gst_pad_peer_query (rp->srcpad, query)) {
+      /* not a problem, just debug a little */
+      GST_DEBUG_OBJECT (rp, "peer ALLOCATION query failed");
+    }
+
+    rp_class->decide_allocation (rp, query);
+    gst_query_unref (query);
+  }
+
   gst_caps_unref (caps);
 
   return rp->negotiated;
diff --git a/gst/rawparse/gstrawparse.h b/gst/rawparse/gstrawparse.h
index 944240bbc..2327dc6fb 100644
--- a/gst/rawparse/gstrawparse.h
+++ b/gst/rawparse/gstrawparse.h
@@ -78,6 +78,7 @@ struct _GstRawParseClass
 
   GstCaps * (*get_caps) (GstRawParse *rp);
   void (*pre_push_buffer) (GstRawParse *rp, GstBuffer *buffer);
+  void (*decide_allocation) (GstRawParse *rp, GstQuery *query);
 
   gboolean multiple_frames_per_buffer;
 };