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Real cost of VOIP calls

fotobits
Rising Star
Posts: 587
Fixes: 1
Registered: 23-06-2007

Real cost of VOIP calls

If the better quality g711a codec is used, I understand that the connection uses about 84kbps, ie about 10kBps.

Since 1GB of file transfers costs 100p, doesn't this mean that a VOIP call incurs a file transfer cost of 1p per second?

Therefore, a call to a BT landline costs a total of 2.5p per second.

Are my maths correct?

Of course, a narrower band Codec would reduce the cost significantly......and the quality!

I would appreciate comments.
10 REPLIES
Community Veteran
Posts: 1,124
Thanks: 4
Registered: 14-08-2007

Real cost of VOIP calls

I think you are out by a factor of 1000.

1GB is aprox. 10000000KB

So the cost is about 0.001 per second for data transfer. This of course takes no account of the cost of the connection from the internet to an actual phone.
fotobits
Rising Star
Posts: 587
Fixes: 1
Registered: 23-06-2007

Real cost of VOIP calls

Thank you so much, Tony, for your prompt reply.

Yes, of course 1G = 1million k, not 1 thousand k

So grateful for your help.....my conclusion seemed so strange!

Regards.........Noel
N/A

Real cost of VOIP calls

The real cost of VoIP is also not the bandwidth, but the cost of the interface into the traditional phone network. This is why most VoIP services are free for computer to computer calls, but have varying costs for computer to landline/mobile calls dependant on the cost incurred by the providers of those services.

Also 1GB is 8,388,608 kilobits.
N/A

gsm codec

The gsm codec is said to be bandwidth efficient whilst giving acceptable quality (like a mobile phone). This should address your bandwidth concerns.
N/A

Re: gsm codec

Quote
The gsm codec is said to be bandwidth efficient whilst giving acceptable quality (like a mobile phone). This should address your bandwidth concerns.


Yep, GSM uses a variable amount of bandwidth - ISTR it's 7-13Kbps.

Out of interest, does PlusTalk support Speex?
pacem
Grafter
Posts: 175
Registered: 07-09-2007

Real cost of VOIP calls

Both GSM and G.729 are popular codecs that are more efficient than the G.711 used by default.
GSM and G.729 use about 30kbs (for 20ms packets including the packet headers) which is 3x better than the ~100kbs used by G.711 (including packet headers).

remeber if you are counting cost that your phone needs to register every few seconds with the SIP server to keep your connection alive. If left on 24x7 this will use about 1GB of data per month so PAYG customers be warned as you'll have to pay the extra £1.50 for that GB and agin for bandwidth used when you actually make calls as well.

(IMHO) The most significant cost consideration when using VoIP is the equipment you are using:

If you plan on leaving your PC on to receive calls expect your electricity bill to increas by about £150 per year; yes a computer that uses 150W of power will cost about £150 per year to run 24x7.

Now consider a proper VoIP phone that will cost you £50 to buy but only cost £5 a year to run...

Alternatively consider that BT provide power to your phone included in the price of the line rental. (and fleece you for each call you make)


That should give some useful information for poeple to dispute/argue about :-)

Paul.<><
fotobits
Rising Star
Posts: 587
Fixes: 1
Registered: 23-06-2007

Real cost of VOIP calls

Most interesting info, Paul. Thank you for your trouble.

I assumed that GSM offered an inferior quality than g711a. I don't find it easy to check codec performance and plumped for G711a, however, I'll have a try 'phoning my own BT landline and get my wife to determine the result!

I'm currently trying to determine whether to purchase a VOIP 'phone or a 'phone adaptor. The adaptor I like is button-switchable between the internet and BT landline, useful. However, the VOIP 'phone would be available for incoming VOIP calls all the time.

Thank you again for your time......

Noel
pacem
Grafter
Posts: 175
Registered: 07-09-2007

Real cost of VOIP calls

I don't actually know if PN support the use of different codecs but if they do you should be able to tell the quality yourself becuase if you chose to send GSM to their system (if it supports it) it will also send GSM back to you.

In terns of quality G.711A is what BT use once your analogue call reaches the exchange. USA phone systems and most VoIP use G.711U but the two can be transcoded without computation expence and without any noticable change in quality.

G.729 is considered to be better quality (and is very slighty more compact) than GSM but requires more CPU power to transcode. G.729a uses the same encoding as G.729 but uses reduced computation and quality. It is still arguable better than GSM. As for speex and ILBM or what ever you can look those up yourself.

Paul.<><
fotobits
Rising Star
Posts: 587
Fixes: 1
Registered: 23-06-2007

Real cost of VOIP calls

Again, many thanks for your trouble, Paul.....

Noel
N/A

Real cost of VOIP calls

Quote
yes a computer that uses 150W of power will cost about £150 per year to run 24x7


Just because a computer says "150W" on the power supply doesn't mean it will always be drawing 150W. When idle a computer will use significantly less power when running flat-out (especially if you use ACPI, etc and spin down the hard drive when idle). This is a good reason why you shouldn't run stuff like SETI@Home since it causes your machine to run flat-out when it would otherwise be idle so it will increase your electricity bill.

Quote
G.729 is considered to be better quality (and is very slighty more compact) than GSM but requires more CPU power to transcode. G.729a uses the same encoding as G.729 but uses reduced computation and quality. It is still arguable better than GSM. As for speex and ILBM or what ever you can look those up yourself.


It's also worth noting that many systems do not support G.729 because it uses patented algorithms and anyone using it has to pay a licence - GSM and Speex, on the other hand, are free for anyone to use.