What codec does plex use for transcoding/syncing music?

When syncing a music playlist on a mobile platform, you can only choose the bitrate/audio quality. But this is relevant only if you know which codec is used for the transcoding. A 192kbps mp3 is not the same as a 192kbps ogg/aac.
So what codec does plex use?

Currently, for Android it is mp3 (and for iOS aac, AFAIR.)