Hi Daniel,

My understanding of this is that Unity Connection can support multiple codecs and avoid transcoding. Have a look;

To Change the Audio Format That Cisco Unity Connection Uses for Calls

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Step 1 In Cisco Unity Connection Administration, expand Telephony Integrations, then click Port Group.

Step 2 On the Search Port Groups page, click the port group that belongs to the phone system integration for which you want to change the audio format of the media stream.

Step 3 On the Port Group Basics page, on the Edit menu, click Codec Advertising.

Step 4 On the Edit Codec Advertising page, click the up and down arrows to change the order of the codecs or to move codecs between the Advertised Codec box and the Unadvertised Codecs box.

If only one codec is in the Advertised Codecs box, Cisco Unity Connection will send the media stream in the that audio format. The phone system will transcode if it does not use this audio format.

If two or more codecs are in the Advertised Codecs box, Connection will advertise its preference for the first codec in the list but will send the media stream in the audio format from the list that the phone system selects.

Step 5 Click Save.

Step 6 (PIMG, TIMG, and SIP integrations only) If you want to change the packet size that is used by the advertised codecs, under Advertised Codec Settings, click the applicable packet setting for each codec and click Save.

Step 7 On the Port Group menu, click Search Port Groups.

Step 8 Repeat Step 2 through Step 7 for all remaining port groups that belong to the phone system integration for which you want to change the audio format of the media stream.

http://www.cisco.com/en/US/docs/voice_ip_comm/connection/2x/administration/guide/2xcucsag140.html

Hope this helps!

Rob