g729 vs ulaw

[logandzwon]

I'm trying to figure out some things as far as CPU load goes.
I know transcoding g729 to ulaw will eat up CPU.
My agents are using polycom phones that support both g729 and ulaw.

1)If I use a T1, does it make a difference which which codec I use?

2)If I use a g729 from handset to a VOIP provider that support g729, is it any different then using a ulaw handset to VOIP procider that uses ulaw?

[okli]

1) Yes, with ulaw there will be no transcoding, thus low CPU usage
2) No, again as above, since there will be no transcoding in both cases, G729 or ulaw all the way

[gmcust3]

So, basically,

If On a server if I have G7290 and I can run 30 seats, with ULaw I cna run more seats ?

[boybawang]

ulaw and alaw has no transcoding, thus lesser cpu load more concurrent calls

[williamconley]

So, basically,

If On a server if I have G7290 and I can run 30 seats, with ULaw I cna run more seats ?

the number of seats means NOTHING. (Sorry)

how many simultaneous phone calls?

if you said: ... run 30 CALLS (not seats) ... then YES absolutely.

The server can have 20,000 seats, but if noone is on the phone right now that means nothing. especially if the sip phones don't register.

that being said: If you meant something along the lines of a 30 seat call center with an average simultaneous live call count of 50 and a "Peak" call count of 75 ... and you are just now noticing that you are hitting your CPU limit ... and if ALL those calls are g729 and you want to know whether changing to ULAW will give you more time before you need to upgrade your server ... YES, it will.

the trick is that this will take lots of bandwidth.

you had g729 because you were low on bandwidth, get more bandwidth and you must pay for that bandwidth every month, but you CAN have more seats.

but if your present bandwidth can handle more g729 calls, get another SERVER and you only pay for it ONCE.

you're the IT guy, so you have to figure out for your boss which way to go (If YOU are the boss, you still have to do the math and work it out!)

[felfel]

1) Yes, with ulaw there will be no transcoding, thus low CPU usage
2) No, again as above, since there will be no transcoding in both cases, G729 or ulaw all the way

1- ok
2- not really true with vicidial, because calls are connected to a meetme (conference) which transcode all codecs to slin (similar to ulaw).
For transcoding cost, you can make "core show translation" in the asterisk (1.4) cli, and you will see the cost of coding and decoding for each codec to others. the most important is transcoding to slin.
for g729 it will cost 2-3 iterations, with ulaw just 1 iteration, for a new core cpu.

What you need to know
- it's better to use ulaw, because of sound quality
- for a call it's better to not transcode, if you use ulaw, use it for all the sections of your connection.


If you have band limitation, what i suggest is to use ulaw in your lan and use g729 for the connection to your provider
if your vicidial server is hosted, than use g729 from your phones to connect to your server and use ulaw from your server to your voip carrier.

[williamconley]

2- not really true with vicidial, because calls are connected to a meetme (conference) which transcode all codecs to slin (similar to ulaw).

actually, that is true but the original question was:

2)If I use a g729 from handset to a VOIP provider that support g729, is it any different then using a ulaw handset to VOIP procider that uses ulaw?

which does not involve vicidial (from handset to provider directly)

it is a good point to bring out, though, that vicidial does not go "from handset to voip provider" directly, everything does go through a meetme transcoded room. clarification is cool.

ulaw is better, but eats up bandwidth, of course, but a call center will not install g729 and pay for those licenses because it's standard policy, but because bandwidth is limited and there is no other way.