diff --git a/HINTS b/HINTS
index 1c95cb197031bc34a0e1d4dbed50fa13b8bcf78d..9749ef4877cf797f359810892311b8ec0f1d3174 100644
--- a/HINTS
+++ b/HINTS
@@ -1,24 +1,29 @@
 the policy format of mediaconch is not well documented yet, here some observations
 (date: 2017-02-20)
 
-- within the policy-xml there are no XML-comments allowed
+- within the policy-xml there are no XML-comments allowed 
+  (will be fixed in upcoming mediaconch version)
+
 - tag <description /> is only allowed on top level, otherwise it will be
-interpreted as a rule with value "true". This could affect the result if next
-real rule fails. Example:
+  interpreted as a rule with value "true". This could affect the result if next
+  real rule fails. Example:
   <policy type="or" name="foo">
     <description>foo</description>
     <rule name="bar" value="baz" tracktype="General" occurrence="*" operator="=">1</rule>
   </policy>
-will always "true", also if <rule name="bar" .. /> fails.
-- there is no way to express an "optional depends". This means you can't
-  express a rule like "Either Audio or not, but if Audio it must be a FLAC"
-
+  will always "true", also if <rule name="bar" .. /> fails.
 
+- to express that either a stream should not exist or exist with given properties, try this:
+  <policy type="or" name="Audio">
+    <rule name="Audio does not exist" value="Default" tracktype="Audio" occurrence="*" operator="must not exist"/>
+    <policy type="or" name="Audio exist">
+      ... <!-- here to check given audio properties -->
+    </policy>
+  </policy>
 
 Expected video-sizes:
 - a good source about videosizes could be https://de.wikipedia.org/wiki/Digital_Intermediate
 
-
 Preservation policy for video material of SLUB:
 - there is no policy offically released yet, please be patient… :)
 
@@ -26,3 +31,4 @@ Howto check files against policy:
 - you need an installed mediaconch
 - on Bash call:
   $> mediaconch --Policy=SLUB_mediaconch_policy_retrodigitized_film35mm.xml -fh file-to-test.mkv > report.html
+
diff --git a/SLUB_mediaconch_policy_retrodigitized_film16mm.xml b/SLUB_mediaconch_policy_retrodigitized_film16mm.xml
index 272cf0f5813a6185f62bd05dca40ffdfd8e39fa1..c09355fb86d689fb508f39c875ca7aa0523c1c7a 100644
--- a/SLUB_mediaconch_policy_retrodigitized_film16mm.xml
+++ b/SLUB_mediaconch_policy_retrodigitized_film16mm.xml
@@ -42,19 +42,22 @@
     </policy>
     
     <policy type="or" name="Audio">
-      <rule name="General/AudioCount is 1" value="AudioCount" tracktype="General" occurrence="*" operator="=">1</rule>
-      <policy type="or" name="Audio is PCM or FLAC">
-        <rule name="Audio is PCM" value="Format" tracktype="Audio" occurrence="*" operator="=">PCM</rule>
-        <rule name="Audio is FLAC" value="Format" tracktype="Audio" occurrence="*" operator="=">FLAC</rule>
-      </policy>
-      <rule name="Audio is 48000 Hz?" value="SamplingRate" tracktype="Audio" occurrence="*" operator="=">48000</rule>
-      <policy type="or" name="Audio is Stereo or Mono?">
-        <rule name="Audio is mono?" value="Channels" tracktype="Audio" occurrence="*" operator="=">1</rule>
-        <rule name="Audio is stereo?" value="Channels" tracktype="Audio" occurrence="*" operator="=">2</rule>
-      </policy>
-      <policy type="or" name="Audio Bit Depth is 16 or 24?">
-        <rule name="Bit Depth is 16?" value="BitDepth" tracktype="Audio" occurrence="*" operator="=">16</rule>
-        <rule name="Bit Depth is 24?" value="BitDepth" tracktype="Audio" occurrence="*" operator="=">24</rule>
+      <rule name="Audio does not exist" value="Default" tracktype="Audio" occurrence="*" operator="must not exist"/>
+      <policy type="or" name="Audio exist">
+        <rule name="General/AudioCount is 1" value="AudioCount" tracktype="General" occurrence="*" operator="=">1</rule>
+        <policy type="or" name="Audio is PCM or FLAC">
+          <rule name="Audio is PCM" value="Format" tracktype="Audio" occurrence="*" operator="=">PCM</rule>
+          <rule name="Audio is FLAC" value="Format" tracktype="Audio" occurrence="*" operator="=">FLAC</rule>
+        </policy>
+        <rule name="Audio is 48000 Hz?" value="SamplingRate" tracktype="Audio" occurrence="*" operator="=">48000</rule>
+        <policy type="or" name="Audio is Stereo or Mono?">
+          <rule name="Audio is mono?" value="Channels" tracktype="Audio" occurrence="*" operator="=">1</rule>
+          <rule name="Audio is stereo?" value="Channels" tracktype="Audio" occurrence="*" operator="=">2</rule>
+        </policy>
+        <policy type="or" name="Audio Bit Depth is 16 or 24?">
+          <rule name="Bit Depth is 16?" value="BitDepth" tracktype="Audio" occurrence="*" operator="=">16</rule>
+          <rule name="Bit Depth is 24?" value="BitDepth" tracktype="Audio" occurrence="*" operator="=">24</rule>
+        </policy>
       </policy>
     </policy>
   </policy>
diff --git a/SLUB_mediaconch_policy_retrodigitized_film35mm.xml b/SLUB_mediaconch_policy_retrodigitized_film35mm.xml
index 54fdde83e216b5e13e39c4e23625e1aef642b9f8..1e9b84186fe48772c54e245fcdf940b4ae218e6e 100644
--- a/SLUB_mediaconch_policy_retrodigitized_film35mm.xml
+++ b/SLUB_mediaconch_policy_retrodigitized_film35mm.xml
@@ -49,6 +49,8 @@
     </policy>
     
     <policy type="or" name="Audio">
+      <rule name="Audio does not exist" value="Default" tracktype="Audio" occurrence="*" operator="must not exist"/>
+      <policy type="or" name="Audio exist">
         <rule name="General/AudioCount is 1" value="AudioCount" tracktype="General" occurrence="*" operator="=">1</rule>
         <policy type="or" name="Audio is PCM or FLAC">
           <rule name="Audio is PCM" value="Format" tracktype="Audio" occurrence="*" operator="=">PCM</rule>
@@ -63,6 +65,7 @@
           <rule name="Bit Depth is 16?" value="BitDepth" tracktype="Audio" occurrence="*" operator="=">16</rule>
           <rule name="Bit Depth is 24?" value="BitDepth" tracktype="Audio" occurrence="*" operator="=">24</rule>
         </policy>
+      </policy>
     </policy>
   </policy>
 </policy>
diff --git a/SLUB_mediaconch_policy_retrodigitized_film8mm.xml b/SLUB_mediaconch_policy_retrodigitized_film8mm.xml
index a557a1ce3a2cd2cd5c628524eb060fabd766d53d..cce0d947565b74219f4bf11be5fcd868e24397ff 100644
--- a/SLUB_mediaconch_policy_retrodigitized_film8mm.xml
+++ b/SLUB_mediaconch_policy_retrodigitized_film8mm.xml
@@ -49,19 +49,22 @@
     </policy>
 
     <policy type="or" name="Audio">
-      <rule name="General/AudioCount is 1" value="AudioCount" tracktype="General" occurrence="*" operator="=">1</rule>
-      <policy type="or" name="Audio is PCM or FLAC">
-        <rule name="Audio is PCM" value="Format" tracktype="Audio" occurrence="*" operator="=">PCM</rule>
-        <rule name="Audio is FLAC" value="Format" tracktype="Audio" occurrence="*" operator="=">FLAC</rule>
-      </policy>
-      <rule name="Audio is 48000 Hz?" value="SamplingRate" tracktype="Audio" occurrence="*" operator="=">48000</rule>
-      <policy type="or" name="Audio is Stereo or Mono?">
-        <rule name="Audio is mono?" value="Channels" tracktype="Audio" occurrence="*" operator="=">1</rule>
-        <rule name="Audio is stereo?" value="Channels" tracktype="Audio" occurrence="*" operator="=">2</rule>
-      </policy>
-      <policy type="or" name="Audio Bit Depth is 16 or 24?">
-        <rule name="Bit Depth is 16?" value="BitDepth" tracktype="Audio" occurrence="*" operator="=">16</rule>
-        <rule name="Bit Depth is 24?" value="BitDepth" tracktype="Audio" occurrence="*" operator="=">24</rule>
+      <rule name="Audio does not exist" value="Default" tracktype="Audio" occurrence="*" operator="must not exist"/>
+      <policy type="or" name="Audio exist">
+        <rule name="General/AudioCount is 1" value="AudioCount" tracktype="General" occurrence="*" operator="=">1</rule>
+        <policy type="or" name="Audio is PCM or FLAC">
+          <rule name="Audio is PCM" value="Format" tracktype="Audio" occurrence="*" operator="=">PCM</rule>
+          <rule name="Audio is FLAC" value="Format" tracktype="Audio" occurrence="*" operator="=">FLAC</rule>
+        </policy>
+        <rule name="Audio is 48000 Hz?" value="SamplingRate" tracktype="Audio" occurrence="*" operator="=">48000</rule>
+        <policy type="or" name="Audio is Stereo or Mono?">
+          <rule name="Audio is mono?" value="Channels" tracktype="Audio" occurrence="*" operator="=">1</rule>
+          <rule name="Audio is stereo?" value="Channels" tracktype="Audio" occurrence="*" operator="=">2</rule>
+        </policy>
+        <policy type="or" name="Audio Bit Depth is 16 or 24?">
+          <rule name="Bit Depth is 16?" value="BitDepth" tracktype="Audio" occurrence="*" operator="=">16</rule>
+          <rule name="Bit Depth is 24?" value="BitDepth" tracktype="Audio" occurrence="*" operator="=">24</rule>
+        </policy>
       </policy>
     </policy>
   </policy>