G729 with Monitor Command

Hi,
I am using G729 in pass through in my asterisk. Now i want to record the conversations between the users.

If I used the command

exten => 124,1,Monitor(g729,4{UNIQUEID})

the recording is done and the files are also made, but the quality of the vox file is so low that i cant hear anything.

If any one can help me

Regards