Proper command escaping

src/FFMpeg/Format/Audio.php

@@ -27,10 +27,9 @@ interface Audio
     public function getKiloBitrate();
 
     /**
-     * Give som extra parameters to add to ffmpeg commandline
-     * Parameters MUST be escaped
+     * Return an array of extra parameters to add to ffmpeg commandline
      *
-     * @return string
+     * @return array()
      */
     public function getExtraParams();
 

src/FFMpeg/Format/Audio/DefaultAudio.php

@@ -31,7 +31,7 @@ abstract class DefaultAudio implements Resamplable, Interactive
      */
     public function getExtraParams()
     {
-        return '';
+        return array();
     }
 
     /**

src/FFMpeg/Format/Video/WebM.php

@@ -28,13 +28,13 @@ class WebM extends DefaultVideo
     {
         return true;
     }
-    
+
     /**
      * {@inheritDoc}
      */
     public function getExtraParams()
     {
-        return '-f webm';
+        return array('-f', 'webm');
     }
 
     /**