vlc的mp4a codec用什么use flag？

mathfeel

我开媒体档时遇到这个错误：

1. No suitable decoder module:
   
2. VLC does not support the audio or video format "mp4a". Unfortunately there is no way for you to fix this.

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但我明明就已经有aac的USE flag:

1. $ eix vlc
   
2. [i] media-video/vlc
   
3.      Available versions:  0.9.8a [M](~)0.9.9_rc [M]**0.9.9999 [M]**9999 {X a52 aac aalib alsa altivec arts atmo avahi bidi cdda cddax cddb cdio dbus dc1394 debug dirac directfb dts dvb dvd esd fbcon ffmpeg flac fluidsynth fontconfig ggi gnome gnutls hal httpd id3tag jack kate libass libcaca libgcrypt libnotify libsysfs libv4l2 lirc live lua matroska mmx modplug mp3 mpeg mtp musepack ncurses nsplugin ogg opengl optimisememory oss pda png pulseaudio pvr qt4 remoteosd rtsp run-as-root samba schroedinger sdl sdl-image seamonkey shine shout skins speex sse stream svg svga taglib theora truetype twolame upnp v4l v4l2 vcdinfo vcdx vlm vorbis win32codecs wma-fixed x264 xinerama xml xosd xv zvbi}
   
4.      Installed versions:  0.9.8a(12:36:56 PM 02/07/2009)(X a52 [color="Red"]aac[/color] aalib alsa avahi bidi cdda cddb dbus directfb dts dvb dvd fbcon ffmpeg flac fontconfig gnome gnutls hal httpd libcaca libgcrypt libnotify mmx modplug mp3 mpeg musepack ncurses nsplugin ogg opengl pda png qt4 samba sdl speex sse svg taglib theora truetype upnp v4l v4l2 vcdinfo vcdx vlm vorbis x264 xinerama xml xosd xv -altivec -arts -atmo -cddax -cdio -dc1394 -debug -dirac -esd -fluidsynth -ggi -id3tag -jack -kate -libass -libsysfs -libv4l2 -lirc -live -lua -matroska -optimisememory -oss -pulseaudio -pvr-remoteosd -rtsp -run-as-root -schroedinger -sdl-image -seamonkey -shout -skins -stream -svga -twolame -win32codecs -zvbi)
   
5.      Homepage:            http://www.videolan.org/vlc/
   
6.      Description:         VLC media player - Video player and streamer

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请问这样不够吗？