FOOD FOR THOUGHT best codec to use

[iworkhere]

Hi All,

What is the best codec to use that has the list issue and best call quality? I heard ulaw but im also reading more on G729. What are peoples thoughts on this?

 

[stanjohn]

In general a uncompressed high data rate codec will sound better provided their are no limits on bandwidth. So it depends the your bandwidth and number of simultaneous calls. G729 and GSM are two popular compressed codecs.

 

[iworkhere]

for an organization with 200 users what do you recommend?

 

[stanjohn]

you need history of this organization's usage to calculate the maximum usage and add a factor of times 1.5 to 4 for growth. the codec is not a factor unless you run out of money and or grow to fast. your internet connection should be dedicated to just voice unless you want to manage the Quality Of Service problems of file transfer, web serving and voice. voice requires as much incoming as outgoing bandwidth which is unlike most other internet connections that may have 10 times as much download vs unload bandwidth so if you have a asymmetric internet connection voice will be limited to the lower rate. If needed you can use multi connections but this has it own challenges.

You are unlikely to get an accurate answer to your question without supplying much more info.

 

[krzykat]

If you are in the US, I'd go with Ulaw. It will have the best quality and its only aversion is the bandwidth it requires. On a 200 user network, I would assume you would have more than sufficient bandwidth (or you should). Also - make certain you have a good QOS router in place (I prefer PFsense) to insure that you have no issues with people using your bandwidth for other items.
The only time I use G.729 is when I'm dealing with international and bandwidth constraints present themselves as a constraint.

 

[hbonath]

I generally use G.722 for internal calls and ulaw on the sip trunk.

 

[atsak]

Yes, hbonath is correct - that will give you the best quality and bandwidth . . . you're wasting bandwidth for G.722 on trunk calls almost all the time still.

 

[hbonath]

What's funny, is that G.722 actually consumes the exact same 64kbps that G.711 does - it just runs a wider Khz band, at 16000Hz instead of the standard 8000Hz used in G.711, which gives you that lower bass and higher treble.
It's just that most carriers I've run across generally only support G.711 or G.729, and some like Vitelity support GSM for a royalty-free low bandwidth experience.

As for Bandwidth on those, the 64Kbps does not account for your packet overhead, as a typical ethernet frame has about 20 bytes of header + frame check, so when estimating bandwidth usage I generally estimate at about ~100Kbps per concurrent call, and shape traffic there. Fun stuff!

 

[EndeavorPBX]

Normally, you want to use Ulaw (aka G711).

That's what you're going to get when your calls go out into the world. Most ITSPs support Ulaw, and when a call reaches the PSTN, its going to use Ulaw.

I tried using G722 internally. Definitely better sound quality internally, but when you place an outgoing call, Asterisk has to transcode when the calls go out onto your trunks. That increases the latency slightly, and the increased call quality internally is not worth it.

If you have a very crummy internet connection or you need to have more simultaneous calls than Ulaw allows with your bandwidth, then you might consider Gsm or G729, if your Trunk provider supports it.