[Asterisk-Users] G729 question

[Clif Jones]

I am thinking about using the G729 codecs on my endpoint devices and
purchasing some G729 licenses for Asterisk but I have several questions:

1. Which G729 codec is sold by Digium for Asterisk, G729, G729A, B...I?
2. If I have G729A on one end and G729B on the other, are they compatible?

I have looked all over the place for question 2, but without buying the 
ITU docs
I cannot seem to find this answer.  I know that G729A is low complexity 
which
seems to be what Cisco 7960's use but I have some others that support G729B
which has comfort noise and reduced transmission during silence.  If 
anyone knows
how the different G729 codecs interoperate I would be eager to know.  
Thanks.