Are you talking about transcoding an audio stream on the fly using DSPs? Or are you asking about converting a g711 wav file to g729 and playing a g729 file? If you are looking to convert files, check out the section titled "Modifying G.729-encoded Prompts and Music-On-Hold Media for Gateway Compatibility" in the CVP 8 release notes found here:
http://www.cisco.com/en/US/docs/voice_ip_comm/cust_contact/contact_center/customer_voice_portal/cvp8_0/release/notes/cvp_801_rnotes.pdf
EDIT - Never mind...I just saw the mention of TTS in your question. I guess I'll leave the info above in case someone else finds it useful. I had heard that they were going to be supporting split codecs again in CVP at some point, but haven't had a chance to read up on it lately.
