filter_chain: add a function to do only filtering

src/misc/filter_chain.c

@@ -444,6 +444,17 @@ static picture_t *FilterChainVideoFilter( chained_filter_t *f, picture_t *p_pic
     return p_pic;
 }
 
+static picture_t *filter_chained( chained_filter_t *f, picture_t *p_pic )
+{
+    for( ; f != NULL; f = f->next )
+    {
+        p_pic = f->filter.ops->filter_video( &f->filter, p_pic );
+        if( unlikely(!p_pic) )
+            break;
+    }
+    return p_pic;
+}
+
 picture_t *filter_chain_VideoFilter( filter_chain_t *p_chain, picture_t *p_pic )
 {
     if( p_pic )