title: Can not create volume interface for an Output Mix object
body: <p>I am having a problem with the volume interface in OpenSL on Android.  When I attempt to create an Output Mix object with the volume interface like this:</p>
  
  <pre><code>const SLInterfaceID interfaceIDs[1]={SL_IID_VOLUME};
  const SLboolean interfaceRequirements[1]={SL_BOOLEAN_TRUE};
  
  SLresult result=(*engineInterface)-&gt;CreateOutputMix(engineInterface,&amp;outputObject,1,interfaceIDs,interfaceRequirements);
  </code></pre>
  
  <p><code>result</code> comes back as <code>SL_RESULT_FEATURE_UNSUPPORTED</code> even though the volume interface is listed as mandated in the <a href="http://www.khronos.org/registry/sles/specs/OpenSL_ES_Specification_1.0.1.pdf" rel="nofollow">spec</a>.</p>
  
  <p>If I change the <code>1</code> to <code>0</code> so that it ignores the requested interfaces, the output mix object is created, but obviously fails when attempt to <code>GetInterface(outputObject,SL_IID_VOLUME,&amp;volumeInterface)</code>.</p>
  
  <p>The only mention of the volume interface I see <a href="http://mobilepearls.com/labs/native-android-api/opensles/index.html" rel="nofollow">here</a> is related to volume calculations when using <code>EnableStereoPosition</code>.</p>