Which MRGL is used to select transcoder when call is made between two phones

[voiphub01]

Friends,

Generally transocder is required in applications like MoH, Conference, CUC etc. MRGL allows to use appropriate transcoder by assigning it to respective device pool under which these application resides.

However when call is made between two phones, RTP in most of the times flow directly between the phones and no transcoder is required. However in case call manager detects codec mismatch between the phones and invoke transcoder, I want to know whether MRGL of calling party will be checked or called party to get the respective transcoder to be used?

Regards

[kkoeper12]

If the Calling phone needs to use a transcoder it will use the MRGL assigned to the Calling device. If the Called phone needs a transcoder it will use the MRGL assined ot the Called phone.

[voiphub01]

Hi Jaime/kkoeper,

Thanks for your comments.

Let's consider phone1 (supports only G729) and transcoder in HQ DP and phone2 (supports only G711) in Branch1. I know this won't be practical scenario but to understand the flow.

Region settings instructs to have call in G.711 between HQ and Branch1.

1. Now if high bandwidth codec requester allocates transcoder from it's MRGL, then phone2 MRGL should be used.

2. If logic checks the MRGL of device which needs transcoding, then it's phone1 who wants codec to convert from G729 to G711.

Would appreciate your further clarification.

Regards 

[kkoeper12 · Accepted solution]

This is a good example of a bad network design. Basically you are saying to use this config:

HQPhone1 --> G729 --> transcode at gateway to G711 --> send G711 over WAN --> G711 from Branch1 gateway to Branch1 Phone2

So, yes, using the configuration you described the MRGL of HQ Phone 1 would be used to transcode G729 to G711 and G711 would be sent over the WAN to Branch1.

The preferred design as Jaime said is to send the low bandwidth codec (G729) over the WAN and transcode from G729 to G711 at the end which needs the high bandwidth codec (G711).

To do this the Region settings between for the trunk or gateway that connects the phones should be set for G729. If there is not a trunk or gateway between them (maybe they are at the same location) then you would set the Region of the 2 phones to use G729 between them.

[voiphub01]

Hi Kkoeper,

Yes, I agree with you this is bad design. This was just to know how xcoder gets invoked during phone to phone call.

Thank you very much for clarification.

Regards

[Jaime Valencia · Accepted solution]

The device that requires the higher BW codec will be the one that allocates the XCODER from the configured MRGL at device level, or device pool level.