There are the follwing options:
- Asterisk has unlimited G729/G723.1 codec support in pass-though mode. Path-though means both end must be same codec same protocol. So call like "H323 G729" <-> "SIP G723.1" will fail.
- Asterisk has commercial support for G729 (http://www.digium.com/en/products/g729codec.php). This allows to use transcoding. So call like
"ISDN-PRI G711 <
> SIP G729" will work. Also call like "H323 GSM <> SIP G729" will also work.
- Asterisk has free codec_g729.so and codec_g723.so that add full transcoding support. For example, call like "H323 G729 <-> SIP G723.1" will go. But using these files in commercial purpose is illegal.