After seeing that nobody replyed to my post I tried to redo the configuration again, more carefully this time.
I did the following:
1. Configure a Hardware transcoder for each Location/Device Pool using the hardware DSPs located in the local voice gateway from each location
2. Configure a Media Resource Group List and Media Resource Group List for each Location/Device Pool containing the previously configured Hardware Transcoders
2. Attach the MRGL to the respective IP Phones and also to the SIP Trunks pointing to the Recording Server (CallREC in my case)
3. Check the "Media Termination Point Required" checkbox in the SIP Trunk configuration page
4. Tested the recording again with every scenario that I could think of and it worked in every situation:
This is aone situation that did not work before:
- IP Phone A (Device Pool A - HW Transcoder from Location A - Recording Profile with Recording Server in different Device Pool) --> IP Phone B (Device Pool A - HW Transcoder in Location A) - codec G.711
- IP Phone A --> SIP Trunk to CallREC Server situated in Location B --> codec G.729
- Now it works with the help of the MTP Required checkbox
Before it did not work because I forgot to check the "MTP Required" checkbox.
The HW Transcoder is required in order to transcode to G.729. Simply configuring a HW transcoder, attaching it to the devices and not checking "MTP Required" checkbox does not solve the problem (this is where i did the mistake previously).
Hope this helps.
If not, let me know, maybe we can find a solution .