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Forcing inbound Codec to G711

 
 
=?ISO-8859-1?Q?=22Pet_=40_www=2Egymratz=2Eco=2Euk_=3B=AC=29=22?=
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      12-08-2006
At a guess I presume inbound numbers from public PSTN routed from ones
VOIP supplier would be routed on the most economical codec eg G712A/B

If that's the case, then if I were to force the voip ports to a single
codec e.g. G711MU, presumably the inbound call would be forced to
upscale to this single codec rather than the lowest it could get away with?

Would there be any forseeable disadvantages doing this?
I see it as a way of getting max. call quality in inbound calls esp.
where downstream bandwidth is not such an issue as upstream.

Any thoughts?
Pete
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alexd
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      12-09-2006
"Pet @ www.gymratz.co.uk ;)" wrote:

> At a guess I presume inbound numbers from public PSTN routed from ones
> VOIP supplier would be routed on the most economical codec eg G712A/B


What do you mean by "economical"? Some codecs cost less bandwidth but more
CPU time. Some codecs are patented [whether legally or not] and require
licensing.

> If that's the case, then if I were to force the voip ports to a single
> codec e.g. G711MU, presumably the inbound call would be forced to
> upscale to this single codec rather than the lowest it could get away
> with?


If it's SIP we're talking about, both ends have to agree on a codec. If they
cannot, the call will fail.

> Would there be any forseeable disadvantages doing this?


Higher bandwidth use.

> I see it as a way of getting max. call quality in inbound calls esp.
> where downstream bandwidth is not such an issue as upstream.


When budgeting bandwidth, it makes sense to assume that it will be
symmetrical. When I watch the bandwidth graph on my Asterisk server [SIP,
G711u], it's always level in both directions, ie it doesn't have peaks and
troughs that correlate with speech and silence. This of course may depend
on silence suppression and voice activity detection settings etc on the
endpoints.

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Philippe Deleye
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      12-09-2006

"Pet @ www.gymratz.co.uk ;)" <(E-Mail Removed)> wrote in message
news:fmgeh.13632$(E-Mail Removed). uk...
> If that's the case, then if I were to force the voip ports to a single
> codec e.g. G711MU, presumably the inbound call would be forced to
> upscale to this single codec rather than the lowest it could get away

with?

If the other end of the call (your Providers PSTN Gateway) does not support
the codec you try to enforce, then the call will fail.

> I see it as a way of getting max. call quality in inbound calls esp.
> where downstream bandwidth is not such an issue as upstream.


There is no connection between inbound calls and downstream bandwith. Both
Inbound calls and outbound are using the same (symmetric) bandwith, if using
the same codec.
With good downstraem bandwith, you will experience good sound quality, but
with a bad upstraeam bandwith the other party will experience bad quality
(what you hear is downstream, what the other party hears is upstream - not
related to incoming our outgoing calls ...


 
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Jono
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      12-10-2006
alexd brought next idea :

>
> When budgeting bandwidth, it makes sense to assume that it will be
> symmetrical. When I watch the bandwidth graph on my Asterisk server [SIP,
> G711u],


How'd you do that?


 
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Paul
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      12-11-2006
Pet @ www.gymratz.co.uk ;) wrote:
> At a guess I presume inbound numbers from public PSTN routed from ones
> VOIP supplier would be routed on the most economical codec eg G712A/B


Not in my experience, most stick to G.711a/u. It's still only needs
about 80kbps per call which is fine for the vast majority of Internet
connections these days. G729 would save on bandwidth but it's CPU
intensive, this might not matter for you but it'll make a big difference
for a service provider. It is also not a free codec and the license
holder must be paid for it. I dare say that most importantly, it's
lower quality than G711 (and therefore the PSTN) so the customer would
perceive the service provider's service as poorer quality.

>
> If that's the case, then if I were to force the voip ports to a single
> codec e.g. G711MU, presumably the inbound call would be forced to
> upscale to this single codec rather than the lowest it could get away with?


Yes if you set your VoIP hardware to only accept g711a/u then either the
service providers server will agree to this or the call will fail.

>
> Would there be any forseeable disadvantages doing this?
> I see it as a way of getting max. call quality in inbound calls esp.
> where downstream bandwidth is not such an issue as upstream.


Less calls through your Internet connection. The calls require the same
amount of bandwidth in either direction regardless of whether they are
incoming calls or outgoing calls.

>
> Any thoughts?
> Pete

 
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ale.cx
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      12-11-2006
On Dec 10, 11:59 am, Jono <(E-Mail Removed)> wrote:

> How'd you do that?


gkrellmd on the Asterisk box, gkrellm on my desktop

alexd

 
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=?ISO-8859-1?Q?=22Pet_=40_www=2Egymratz=2Eco=2Euk_=3B=AC=29=22?=
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      12-11-2006
Paul wrote:

> Not in my experience, most stick to G.711a/u. It's still only needs
> about 80kbps per call which is fine for the vast majority of Internet
> connections these days. G729 would save on bandwidth but it's CPU
> intensive, this might not matter for you but it'll make a big difference
> for a service provider. It is also not a free codec and the license
> holder must be paid for it. I dare say that most importantly, it's
> lower quality than G711 (and therefore the PSTN) so the customer would
> perceive the service provider's service as poorer quality.


I was just going down the train of thought based on last weeks incoming
calls, though, they were being routed through a sipgate number when our
BT line was busy. Since then I have signed up to voipfone.co.uk mainly
for incoming calls (on BT busy) but also for the CLI on outgoing calls
should we have anyone that decides not to answer "no ID/International"
calls from voipcheap.com

<snip>

> Less calls through your Internet connection. The calls require the same
> amount of bandwidth in either direction regardless of whether they are
> incoming calls or outgoing calls.


I'll leave it with multiple codecs available then and see how we go.

On a further note, if I have 2 outgoing lines via router do I need to
specify a range of SIP ports
e.g. 5060-5061 for line 1 and 5062 - 5063 for line 2

At the moment all accounts are left at 5060.

Cheers
Pete


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ale.cx
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      12-12-2006
On Dec 11, 2:12 pm, "Pet @ www.gymratz.co.uk ;)"
<(E-Mail Removed)> wrote:

> On a further note, if I have 2 outgoing lines via router do I need to
> specify a range of SIP ports
> e.g. 5060-5061 for line 1 and 5062 - 5063 for line 2


For outgoing you don't need to forward any ports so long as your router
does NAT and the firewall rules don't block it.

For incoming it's slightly different. If it's one physical device [eg a
single router, ATA or Asterisk server] with multiple accounts on, the
device should be able to deduce from the info in the inbound call which
account the call is for. SIP calls are a bit like email addresses, the
bit before the '@' is the account that the call is for.

If you've got multiple devices registering their own accounts behind a
single public IP address, you will need to make sure the relevant ports
are forwarded to the relevant devices for them to be able to receive
calls.

> At the moment all accounts are left at 5060.


Does it work?

 
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=?ISO-8859-1?Q?=22Pet_=40_www=2Egymratz=2Eco=2Euk_=3B=AC=29=22?=
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      12-12-2006
ale.cx wrote:

> For outgoing you don't need to forward any ports so long as your router
> does NAT and the firewall rules don't block it.


That'd be ok then.
It's only multiple outgoing calls that concerned me.

> For incoming it's slightly different. If it's one physical device [eg a
> single router, ATA or Asterisk server] with multiple accounts on, the
> device should be able to deduce from the info in the inbound call which
> account the call is for. SIP calls are a bit like email addresses, the
> bit before the '@' is the account that the call is for.
>
> If you've got multiple devices registering their own accounts behind a
> single public IP address, you will need to make sure the relevant ports
> are forwarded to the relevant devices for them to be able to receive
> calls.


>> At the moment all accounts are left at 5060.

>
> Does it work?


I haven't really tried it in anger.
Currently incoming BT calls are set to divert to 0845 number provided by
voipfone should the bt line be busy. from there both voip ports on the
router ring so should bt line be tied up and port 1 also tied up then
port 2 should get the call.

We don't generally get enough calls to try it and most of the time
there's only 2 of us here anyway.
:)

It just seemed that when I was trying to make 2 outgoing voip calls at
the same time I was getting a busy tone, hence the reason for the post.

May just have been a coincidence though.

Cheers
Pete


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PeterW
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      12-18-2006
Paul <(E-Mail Removed)> wrote in
news:457d2a89$0$624$(E-Mail Removed):

> Pet @ www.gymratz.co.uk ;) wrote:
>> At a guess I presume inbound numbers from public PSTN routed from
>> ones VOIP supplier would be routed on the most economical codec eg
>> G712A/B

>
> Not in my experience, most stick to G.711a/u. It's still only needs
> about 80kbps per call which is fine for the vast majority of Internet
> connections these days. G729 would save on bandwidth but it's CPU
> intensive, this might not matter for you but it'll make a big
> difference for a service provider. It is also not a free codec and
> the license holder must be paid for it. I dare say that most
> importantly, it's lower quality than G711 (and therefore the PSTN) so
> the customer would perceive the service provider's service as poorer
> quality.
>
>>
>> If that's the case, then if I were to force the voip ports to a
>> single codec e.g. G711MU, presumably the inbound call would be forced
>> to upscale to this single codec rather than the lowest it could get
>> away with?

>
> Yes if you set your VoIP hardware to only accept g711a/u then either
> the service providers server will agree to this or the call will fail.
>
>>
>> Would there be any forseeable disadvantages doing this?
>> I see it as a way of getting max. call quality in inbound calls esp.
>> where downstream bandwidth is not such an issue as upstream.

>
> Less calls through your Internet connection. The calls require the
> same amount of bandwidth in either direction regardless of whether
> they are incoming calls or outgoing calls.
>
>>
>> Any thoughts?
>> Pete

>


Most offer G.711a (this is the European/worldwide standard). It provides
the best 8khz sampled audio available.

G.711u is a US standard. G.726/729 or other compression standards (GSM,
Speex etc.) is only useful where bandwidth is a big issue.

peter
 
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