Hi, I am a bit confused about when to use transcoding and when not. When it says "Calls across HQ and BR1 should be g729" and you have a skinny phone versus a sip phone i see at the solutions always: We need to add a transcoder... Why could we not just use multiple codecs via the codec class? As far as i know SIP Phones support G.729 and i got them without transcoder working also via a Sip Trunk: HQ(CCM) --- SIP Trunk ---- BR1(CME-SIP) I have a DevicePool/Region with G729 configured and under CME i've got: voice class codec 1 codec preference 1 g729r8 bytes 20 codec preference 2 g711ulaw bytes 160 ! voice register pool 2 voice-class codec 1 ....etc dial-peer voice 1000 voip voice-class codec 1 ...etc On the other hand when i have a look at the release notes: <snip> G.729a and G.729b Codecs Over SIP Trunks You can use G.729a and G.729b, which are low-bandwidth codecs, for calls that are initiated over SIP trunks. Consider this feature as required for endpoints that do not support delayed media calls and do not want to use a higher-bandwidth codec, such as G.711. Because an MTP needs to be preallocated for early-offer calls, you must configure an external MTP or transcoder device to use this feature. The software MTP does not support G.729 over SIP trunks. Although this feature supports all four G.729 codecs (G.729, G.729a, G.729b, and G.729ab), the system cannot distinguish between G.729 and G.729a or between G.729b and G.729ab. Therefore, Cisco Unified Communications Manager Administration provides only two options for configuring these codecs on SIP trunks: G729/G729a and G729b/G729ab. The G.729 codec over SIP trunks applies only to outgoing calls, and incoming calls do not get affected. Be aware that the system does not support mid-call codec switching from G.729 to any other codec. Cisco Unified Communications Manager Administration Configuration Tips In Cisco Unified Communications Manager Administration, you can enable G.728a and G.729b codecs for the MTP Preferred Originating Codec. -------------------------------------------------------------------------------- Note To configure G.729 codecs for use with a SIP trunk, you must use a hardware MTP or transcoder that supports the G.729 codec. For more information, see "Transcoders" in the Cisco Unified Communications Manager System Guide. </snip> It says: "Because an MTP needs to be preallocated for early-offer calls" .... and when i not use early-offer? i don't need an external MTP? Can someone please shed some light on this? I do not want to loose points because i haven't configured a transcoder... cheers, Bernhard
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