G.729 Question


#1

i wonder if someone help me to understand this, i have Asterisk server in VA and have remote extension in DC i would like to use G.729 codec in this case , i have Broadvoice trunk but my question is can i make outgoing call from the remote extension using Broadvoice trunk with G.729? since there is Asterisk server at the middle i know that Broadvoice doesn’t support that codec but is that something asterisk can do? if not could you please tell me which service provider support it.


#2

Yes, Asterisk may perform transcoding between G729 and G711 (or which ever codec you use with Broadvoice) for you. This would allow your Asterisk endpoints to use G729 while another codec with your Broadvoice service.

In this case you are not using G729 in pass through mode (ie - you are transcoding), therefore you must purchase the appropriate number of licenses for your Asterisk server. Have a look here:

digium.com/index.php?menu=pr … gory=codec

While the gsm codec is not as compressed, it may also serve your purposes if you decided not to go with G729. Also, Broadvoice most likely supports gsm, and therefore you may reduce the load on your Asterisk server by not having to do transcoding. There is always a give and take when making decisions on codecs. Have a look here for further discussion:

forums.digium.com/viewtopic.php?t=119


#3

my only concern is to have better voice quality with low bandwidth, so for example if i purchase G729 codec license and use broadvoice with G.711 the remote extension sould hear better sound than it is now and the load will be on the server since it is transcoding the codecs. am i correct? what about the bandwidth for the server, for example if i get 10 lines from broadvoice and having 10 concurrent calls using G.711 do i consider any more load from the remote extensions using G.729? sorry for all the questions but i need to make sure before i order everything.


#4

I am not familiar with your network environment, therefore I may not specifically comment on what makes the most sense. Your server will still require the bandwidth for 10 concurrent G729 calls and 10 concurrent G711 calls. Further, the load on the server will increase as it must now transcode 10 concurrent calls.

There may be a balance, where gsm or ilbc may provide enough compression, and if Broadvoice supports them then you have no transcoding on the server.

Therefore, what you must consider is this:

  • G729 <-> G711
  • gsm <-> gsm

The gsm may actually have the same overall bandwidth consumption, but with less load on the server. More details for your analysis may be found here:

voip-info.org/wiki-Bandwidth+consumption


#5

Thank you , your answer helped me a lot