a2dp codec selection

hi,
i am using a2dp to connect my bluetooth headphones to my pc. the headphones are supporting the mandatory sbc codec and additionally the aac and aptX codecs. the following defines in profiles/audio/a2dp-codecs.h let me assume that at least sbc, mp3, aac and atrac are supported audio codecs by bluez:

#define A2DP_CODEC_SBC 0x00
#define A2DP_CODEC_MPEG12 0x01
#define A2DP_CODEC_MPEG24 0x02
#define A2DP_CODEC_ATRAC 0x03
#define A2DP_CODEC_VENDOR 0xFF

i want to use the aac codec for the best audio quality. therefore i added the following lines to my /etc/bluetooth/audio.conf

[A2DP]
SBCSources=0
MPEG24Sources=1

is there any possibility to check which codec is currently used if a a2dp link is established? i want to confirm that aac is really used, or if i am using sbc, which bitrate is selected.

i am using ubuntu 12.10.

regards, tropp