Add VideoInterface getPasses method

src/FFMpeg/Format/Video.php

@@ -18,5 +18,10 @@ namespace FFMpeg\Format;
  */
 interface Video extends Audio
 {
-
+    /**
+     * Returns the number of passes
+     *
+     * @return string
+     */
+    public function getPasses();
 }

src/FFMpeg/Format/Video/DefaultVideo.php

@@ -222,4 +222,12 @@ abstract class DefaultVideo extends DefaultAudio implements Interactive, Resampl
 
         return $this;
     }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function getPasses()
+    {
+        return 1;
+    }
 }

src/FFMpeg/Format/Video/X264.php

@@ -44,4 +44,12 @@ class X264 extends DefaultVideo
     {
         return array('libx264');
     }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function getPasses()
+    {
+        return 2;
+    }
 }