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Bandwidth & CPU use


buddbrother
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I believe (this is off the top of my head) that the bandwidth usage is around:

 

64 - 68 kbps when set to high quality (G711)

 

13 - 15 kbps when set to low quality (GSM)

 

 

So on a 256kbps line (assuming you were able to guarantee 256kbps bandwidth all the time which is very unlikely), you would be looking at an absolute maximum of 4 calls on high quality and about 18 calls on low quality.

 

To change the quality, go into Settings > Telephony > Choose a line and click Properties > Advanced

 

So this means to accommodate say 200 high quality calls (as you were asking about in another topic), you would need to have at least around 13 mbit in bandwidth.

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Thanks!

 

How much bandwidth does the "default settings (Recommended)" use and which codec is that?

 

Also if my VoIP provider says that it supports " G.711 ulaw or G.729 ", which of the three: better quality, default, and lower quality am I restricted to, if any?

 

Thanks!

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Well alaw and ulaw are both part of the G711 codec, so you really only listed 2 codecs. One of which (G729) NCH doesn't support (it is not an open or free codec). So if your VoIP provider only supports those codecs, your only option is to go with G711 which gives the highest quality but takes up a huge amount of bandwidth. Just to give you an idea, G729 is considered by many to be the "best" codec when you consider that it provides a quality close to that of G711 but for only a fraction of the bandwidth use. Unfortunately as I said this is not an option.

 

GSM is still an ok codec, but I wouldn't recommend it.. its quality is comparable to your average cellphone/mobile phone and the audio is definitely not as clear as the other codecs.

 

 

Edit: Ok I double checked what exactly the "Default settings" option does. Apparently it allows the software to determine the best codec to use and balance out quality with bandwidth.

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So your provider has a lot to do with it. I have a bandwidth meter installed and with one call I got the following results for both upload and download.

 

For my first provider, sipnumber.com:

 

Low quality: max of 5 to 6 kbps

default: max of 10 to 12 kbps

High quality: max of 10 to 13 kbps.

 

My other provider, gizmo project:

 

Low quality: max of 10-13 kbps

default: max of 10-13 kbps

High Quality: max of 10-13

 

Multiple calls were just multiples of these values!

 

Could this be right? It is way below what you said. Could it be a codec they are using? The codecs I listed above were for a provider other than these two. Maybe these two only provide GSM. However, I do notice a quality change on different settings on the sipnumber, but not really the gizmo. This would be fitting to the bandwidths used on each.

 

Thanks,

 

Jason

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Well G711 uses 64kbps and that is universal standard. So if it is using less than that in bandwidth (such as the 10-13kbps), there is no way it could be using the G711 codec... that sounds more like the GSM codec. And if you're getting 5-6kbps.. there must be another codec IVM supports that I'm not aware of that uses even less bandwidth (but no doubt probably provides even less quality than GSM).

 

Edit: Ok I checked and the other low bandwidth codec that IVM supports must be G.723.1 (when you look at it in terms of bandwidth usage). Here is a full chart with all the VoIP codecs and the bandwidth they use.

http://www.voipforo.com/en/codec/codecs.php

 

So far we know IVM supports

G.711 ~ 64kbps

GSM ~ 13kbps

G.723.1 ~ 6 kbps

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What's interesting is that there is no quality issue with the 10-13 kbps. Maybe that's because all of this time, I've never heard anything greater on the system!

 

But, when my business gets up and running, I might just shoot for GSM. The quality is fine and it will allow me to handle all of the calls I need on a 100 Mbps connection!

 

Thanks for your help.

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Just remember that a 100 mbps LAN connection is simply a measure of the bandwidth available in your internal network. The bandwidth of your internet connection is the real determining factor for calls to and from outside callers. If you are unsure of how much bandwidth you have available of your internet connection, you can use a 'speed meter' such as the one on http://speedtest.net to get a fairly accurate assessment. It is very unusual to find an internet connection that can provide 100 mbps in bandwidth, most range anywhere from 256 kbps to 8 mbps.

 

Also I double checked and GSM is the same codec used for cellular telephony, so the call quality will be almost exactly like that of cellular calls. I should warn you though, from my own personal experience, if a cellular phone calls a VoIP phone which is also using the GSM codec, the quality gets pretty bad.

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Hi,

 

Understood. I would be running this off of a server at ThePlanet so I would actually have close to a 100 Mbps internet connection.

 

In terms of cell phone codecs used, do you know of a site that lists them? A high portion of the calls would be from cell phones. I tried it with some cell phones and haven't had poor quality. Those were mostly on Verizon Phones, so I suppose it could be different for other carriers.

 

Thanks,

 

Jason

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Well any phone that uses a GSM sim card (as opposed to a 3G or CDMA or other service) will be using the GSM codec. That is still a high portion of phones and GSM isn't being phased out anytime soon. I believe it is the most popular cellular network codec used worldwide, at least for now until 3G networks replace it.

 

In the United States Cingular, AT&T, and T-Mobile all use GSM while Sprint, Verizon, and Virgin use CDMA.

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That's very strange. I suspect the support person just doesn't realize that they also support GSM. I know that sometimes I find the same thing where they don't list GSM as one of the available codecs in their FAQ, yet it seems it can be used. I'm not sure if it's because it is not used that often compared to the other codecs or why they choose to exclude it.

 

You should be able to turn on SIP tracing in IVM and look in the logs to confirm for sure what codec is being used.

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I am so confused now. I talked to a guy at sipnumber.com and he says they support GSM, but standard is g.711. In the 3CX PBX software that I'm using, I can even specify which codec to use. Even though I tell it to use g.711, I am still only using 10-13 kbps.

 

I don't get it. I don't mind, because it's the best call quality I've been able to get and the service will be super cheap!! This is even with me telling IVM to use higher bandwidth and make GSM the priority codec!

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