--- a/video.rst	Thu Dec 19 13:46:22 2013 +0200
+++ b/video.rst	Fri Dec 20 22:43:44 2013 +0200
@@ -61,7 +61,10 @@
 
 Extract audio from video file.
 ==============================
-::
+
+``$NO`` - autio strean number::
+
+  $ ffmpeg -i $IN -c:a:$NO $OUT.pm3
 
   $ mplayer -ao pcm:fast:file=audio.wav -vc null -vo null  input.avi