Codec Support: E1 PRI

Unanswered Question
Dec 10th, 2007


I have NM-HDV-2T1/E1 card where e1 PRI is terminated.

Will this PRI support Voice Calls on G.729 codec.Is there any effect on the Voice quality ?

What are the best practises for Codec while configuring the PRI for PSTN interface ?

I have this problem too.
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hemant.wavhal Mon, 12/17/2007 - 06:57


Thanks !!

But i can see that codec used for the calls across PRI is g.729r8.Also reported no severe effect on Voice quality.

Will this be fine or do i need to configure separate region with g711ulaw codec for PRIs ?

Paolo Bevilacqua Mon, 12/17/2007 - 07:00


What Brandon meant, is that codec on the PRI circuit itself is always G711 (u-law or a-law depending on where you are).

Then, the VoIP portion of the call can be g.729 with good quality. This you can change if you want.

hemant.wavhal Mon, 12/17/2007 - 07:16


Does it mean that even if i see codec as g729r8 on Show Voice call Summary command, PRI does the conversion from G729r8 to g711ulaw for outbound calls and vice versa for inbound calls ?

Paolo Bevilacqua Mon, 12/17/2007 - 07:18

Yes. In fact, the conversion is always bidirectional no matter if the call is incoming or outgoing, because a voice call has always one transmit and one receive path.

iptuser55 Tue, 12/18/2007 - 03:19

I have set up whereby we have cluster in country A with a remote GW running Q Sig going to a PABX in Country B. To reduce BW across the WAN we have regions set up- Calls A to B use g729, Are you saying that calls will be g729 from and to the GW but the actual GW will change them going to the PABX from G729 to G711 automatcailly . We have problems with volume- tried changing the iput gain and attenuation before .


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