# Compilation error with media9 package

While using media9 package, I'm getting the following error :

Argument of \bool_if:nTF has an extra }


I'm unable to figure out where does the error come from. Here is the minimal example:

\documentclass{beamer}
\mode<presentation>
\usepackage{media9}
\setbeamercovered{transparent}

\begin{document}
\begin{frame}
\includemedia[
activate=pageopen,
width=200pt,height=150pt,
flashvars={%
source=c4.mp4
}
]{}{VLC.app}%{VPlayer.swf}
\end{frame}
\end{document}

-
You must use most recent l3kernel, l3packages and media9 packages. Update your TeX distribution. If you have TeXLive-2012, run tlmgr update --self --all. You cannot use VLC with this method. If you want a player with controls, use StrobeMediaPlayback.swf. See media9 package documentation and the examples therein. Note that source setting via flashvars for Strobe is slightly different from VPlayer. VPlayer.swf and StrobeMediaPlayback.swf are part of media9. –  AlexG Jul 31 '12 at 12:18
@AlexG This looks like a bug to me. Line 772 of media9.sty (v0.8) has \msg_error:nnxx{media9}{file~not~found}{#1}, but this should be \msg_error:nnx{media9}{file~not~found}{#1} (or probably the new \msg_error:nnn). –  Joseph Wright Jul 31 '12 at 12:19
Thanks again @AlexG. I've updated all the packages and I'm yet getting the same error. Is it due to the fact that the file (in my code VLC.app) is not found? –  rasha Jul 31 '12 at 12:32
Thanks, @Joseph. I'll upload a corrected version. Will the x-variants be removed? How to ensure expansion of the argument if, for instance, the user provides a macro with the file name? –  AlexG Jul 31 '12 at 12:35
@AlexG The variants will be retained: we have simply 'tidied up' the definitions such that they are now based 'properly' on n-type base functions. Of course, if you allow names to be stored in macros then you do want the x-type variant. –  Joseph Wright Jul 31 '12 at 12:40
As Joseph Wright pointed out, I can confirm that this is a bug in media9.sty, if you replace "\msg_error:nnxx{media9}{file~not~found}{#1}" by "\msg_error:nnn{media9}{file~not~found}{#1}", there will be no error. However this points out to the fact that your file 'c4.mp4' doesn't exists or is not found.