Force GSM codec to save bandwith in 3CX system

[toby_rdc]

I have a 3CX phone system at a central point and at our remote offices we are using 3CX VOIP PHONES. Between the offices we have satellite communication with limited bandwith. There are no landlines here nor any fibers, satellite is teh only way. Everything is working fine but the system always use THE PCM codecs which takes to much bandwith for us. It is also a problemm with other internet usage at the same time as the line get slow. I want only to use the GSM codec if possible jsut for the 3CX phones which are at remote offices if not i want to force GSM codec on all clients. As GSM should not occupy more the 16 kbit it wouls suite as much better. I have tried to change the prority settings in 3CX phone but it is always PCM anyway .
I am searching for step by step instruction on how to force the 3CX system to just use the GSM codec . Maybe it is an RTFM but i have not managed to found it. GSM codec is stated on the homepage of 3CX that it should be included in the free version. If this is not correct, please tell me and i will buy the commersial version directly but i have to know all the facts. All your tecnichians out there, please help me out with this one.

Best regards
Toby

 

[KerryG]

In the 3CX VoIP Phone did you go to the Advanced Settings and move GSM to the top of the list?

 

[toby_rdc]

Yes, have been testing all combinations, but the result is always the the system choses PCM

 

[Vali_3CX]

Yes, have been testing all combinations, but the result is always the the system choses PCM

Hi, Toby
The reason might be that there are several GSM codec types, so if they don't match, PCM will be chosed.

 

[toby_rdc]

I am using 3CX Voip phone and GSM with the VOIP phone should be compatible with GSM codec in 3CX phone systen.

 

[Vali_3CX]

I am using 3CX Voip phone and GSM with the VOIP phone should be compatible with GSM codec in 3CX phone systen.

Hmm :roll: I don't think this matching is required between PBX and 3CXPhone, but between the two phones, of course excepting the case when call is bound to PBX media server - you may try to do this.

 

[nb]

I think I need to understand better the network and 3CX topology because you mentioned that you have remote offices. It depends on the nature of the call you want to do. How are the remote offices connected? yes by Satellite but tell me the entities between the remote offices - Bridge, Tunnel, direct over the internet?

Internally (on the internal network) you do not need to restrict to the GSM codec. You want the GSM codec on outbound calls. The outbound entity must be configured ONLY with the GSM codec enabled. This way the media server will ONLY offer GSM and nothing else. So then either the provider likes GSM or else no audio at all.

The voip phone will not refuse to offer PCMU or PCMA, but if GSM is at the top of the list and the other entity is configured the same, they will speak in the First Matched codec which is GSM.

Let me know.

 

[toby_rdc]

We have one 3cx server on our main office which is also just conencted to a SAT conenction. We have 3CX voip clients connected at our remote offices also via VSAT connections. We use 3CX system to communicate between offices as even the GSM network does not work well here. We do noy have any trunks etc, it is only for comms between our main office and remote offices. to communicate the users use 3CX voipphone. I want to use the GSM codec always as the VSAT speed is only 256 kbit /s. I therefore need to save bandwith as much as possible. It works with PCM as well but when the load on the satcom gets to high the speech is sometimes cut. At our main office we have 1 Mbit/s . Ofcourse communicating within the main office is not a problem as there they communicate on the LAN. We are using VPN tunnels so the users always use direct connection to the 3CX server even when at the remote offices. The question is about ensure that traffic between 3CX VOIP phones should use GSM codec to save bandwith

/Toby

 

[nb]

If the Voip phones are configured both with GSM first, the sdp offer model will give GSM as the first priority in the order of the codec list. This is confirmed and

Any bridges you have should have GSM as the only codec.
Any Voip providers should have GSM as the only codec.

Make a capture and see what is happening.

 

[SteveY]

Hi
I don't know if you fixed your problem yet, but we have a similar situation coming up with our client who has the main site in the UK and a remote office in India - bandwidth is very limted. I have downloaded and been playing with a different soft phone called X-Lite

http://www.counterpath.net/x-lite.html&active=4

I haven't had any compatibility problems so far with 3CX, and the useful thing about X-Lite is that you can disable codecs, i.e. just leave the GSM codec enabled.
To configure the codecs, right click on the phone screen select options and then Advanced in bottom left.

I hope this helps.

 

[Discovery Technology]

I've read somewhere that you could use 'pbx delivers audio' to tie a codec to a call - this may be worthwhile trying also, on one of the remote extensions.

 

[nb]

Frankly speaking there is nothing to fix.

It is a question of configuration. Xlite has the option to disable codecs and we don't. If you have both phones with GSM first, they will talk using GSM. Also if you enable GSM on the tunnel or bridge only, you will definitely use the GSM codec.