diff --git a/av/sidedata/sidedata.pyx b/av/sidedata/sidedata.pyx
index 9b423a30b..c7070c34f 100644
--- a/av/sidedata/sidedata.pyx
+++ b/av/sidedata/sidedata.pyx
@@ -88,7 +88,21 @@ cdef class _SideDataContainer:
 
         type_ = Type.get(key)
         return self._by_type[type_]
+    
+     def add(self, buffer, type):
+        # Add Frame side data
+        cdef ByteSource source = bytesource(buffer)
+        i = self.frame.ptr.nb_side_data
+        lib.av_frame_make_writable(self.frame.ptr)
+        ptr = lib.av_frame_new_side_data(self.frame.ptr, type, source.length)
 
+        memcpy(ptr.data, source.ptr, source.length)
+
+        # Update side_data
+
+        cdef SideData data = wrap_side_data(self.frame, i)
+        self._by_index.append(data)
+        self._by_type[data.type] = data
 
 class SideDataContainer(_SideDataContainer, Mapping):
     pass