diff -r 05898b7a0a73 -r 4d725464e237 src/pyams_media/converter.py
--- a/src/pyams_media/converter.py	Fri Oct 13 09:08:48 2017 +0200
+++ b/src/pyams_media/converter.py	Fri Oct 13 09:09:23 2017 +0200
@@ -199,6 +199,7 @@
     require_temp_file = True
 
     def add_common_filters(self, document):
+        super(Mp4VideoConverter, self).add_common_filters(document)
         effects = document.__effects__
         effects['filter:v'] = 'setsar=1/1'
         effects['pix_fmt'] = 'yuv420p'
@@ -227,6 +228,7 @@
     require_temp_file = True
 
     def add_common_filters(self, document):
+        super(WebmVideoConverter, self).add_common_filters(document)
         effects = document.__effects__
         effects['filter:v'] = 'setsar=1/1'
         effects['pix_fmt'] = 'yuv420p'