diff --git a/sdk/plugins/filter.cpp b/sdk/plugins/filter.cpp
index 15fe345..1e28ba5 100644
--- a/sdk/plugins/filter.cpp
+++ b/sdk/plugins/filter.cpp
@@ -153,6 +153,7 @@ class CSDN : public UntrainableTransform
             }
         }
 
+     m.convertTo(m, CV_8UC1);
      dst = m;
 
     }