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seandarcy2 at gmail.com
Guest
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 Posted: Tue Feb 19, 2008 10:50 pm Post subject: [asterisk-users] which codec over iax => pstn |
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using asterisk(A) over iax to another asterisk server(B) which connects
to pstn over pri.
Doesn't B have translate to ulaw whatever goes out to the pstn, so
therefore shouldn't A choose ulaw as the iax codec to B? That way
there's no loss translating from {gsm, ildc, etc} to ulaw on the B server.
My partner thinks I'm nuts, and that gsm is much more "efficient" as the
iax codec.
BTW, we have 512kbs over the iax connection.
Whom do you support?
sean |
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gordon+asterisk at dro...
Guest
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| Posted: Wed Feb 20, 2008 7:56 am Post subject: [asterisk-users] which codec over iax => pstn |
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On Tue, 19 Feb 2008, sean darcy wrote:
| Quote: | using asterisk(A) over iax to another asterisk server(B) which connects
to pstn over pri.
Doesn't B have translate to ulaw whatever goes out to the pstn,
|
Depends on the country, but ulaw or alaw...
| Quote: | so
therefore shouldn't A choose ulaw as the iax codec to B? That way
there's no loss translating from {gsm, ildc, etc} to ulaw on the B server.
|
It depends on how the call comes into A and how "bothered" A is about
doing the transcoding, or letting B do it for them.
If the calls come into A via GSM, then you might as well send them out
again in GSM as the call quality won't improve, but if they come into A as
G711 (ulaw or ulaw) then keep them as G711 if you don't want to lose
quality, else compress them to GSM if you don't have the bandwidth
avalable.
| Quote: | My partner thinks I'm nuts, and that gsm is much more "efficient" as the
iax codec.
|
GSM is more compressed than ulaw or alaw, so will use less bandwidth, but
in doing so, it will sound worse. (mobile phone quality rather than
landline quality)
| Quote: | BTW, we have 512kbs over the iax connection.
|
G711 needs about 80Kb/sec each way to work. (It's 64Kb/sec plus IP
overhead). GSM needs about 32Kb/sec (13Kb/sec plus IP overhead).
IAX is more efficient than SIP in packing multiple calls into the one data
stream.
| Quote: | Whom do you support?
|
My customers, and what they ask for...
Gordon |
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seandarcy2 at gmail.com
Guest
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| Posted: Wed Feb 20, 2008 9:00 am Post subject: [asterisk-users] which codec over iax => pstn |
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Gordon Henderson wrote:
| Quote: | On Tue, 19 Feb 2008, sean darcy wrote:
| Quote: | using asterisk(A) over iax to another asterisk server(B) which connects
to pstn over pri.
Doesn't B have translate to ulaw whatever goes out to the pstn,
|
Depends on the country, but ulaw or alaw...
|
ulaw
| Quote: |
| Quote: | so
therefore shouldn't A choose ulaw as the iax codec to B? That way
there's no loss translating from {gsm, ildc, etc} to ulaw on the B server.
|
It depends on how the call comes into A and how "bothered" A is about
doing the transcoding, or letting B do it for them.
|
the call comes into A over an analog port on a TDM400P. I assume it's ulaw.
| Quote: | If the calls come into A via GSM, then you might as well send them out
again in GSM as the call quality won't improve, but if they come into A as
G711 (ulaw or ulaw) then keep them as G711 if you don't want to lose
quality, else compress them to GSM if you don't have the bandwidth
avalable.
| Quote: | My partner thinks I'm nuts, and that gsm is much more "efficient" as the
iax codec.
|
GSM is more compressed than ulaw or alaw, so will use less bandwidth, but
in doing so, it will sound worse. (mobile phone quality rather than
landline quality)
| Quote: | BTW, we have 512kbs over the iax connection.
|
G711 needs about 80Kb/sec each way to work. (It's 64Kb/sec plus IP
overhead). GSM needs about 32Kb/sec (13Kb/sec plus IP overhead).
|
So with DSL 512kbs up and 3mbs down, plenty of room for G711.
Of course, I could figure out how to configure QOS in iptables for
asterisk, it'd be a lot better.
| Quote: | IAX is more efficient than SIP in packing multiple calls into the one data
stream.
| Quote: | Whom do you support?
|
My customers, and what they ask for...
|
Great. Thanks for the help.
sean |
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gordon+asterisk at dro...
Guest
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| Posted: Wed Feb 20, 2008 9:19 am Post subject: [asterisk-users] which codec over iax => pstn |
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On Wed, 20 Feb 2008, sean darcy wrote:
| Quote: | | Quote: | G711 needs about 80Kb/sec each way to work. (It's 64Kb/sec plus IP
overhead). GSM needs about 32Kb/sec (13Kb/sec plus IP overhead).
|
So with DSL 512kbs up and 3mbs down, plenty of room for G711.
|
Probably. I've found that it's not the absolute speed that matters, but
the quality of your connectivity ISP that's as crucial. IN theory you can
support 5 or 6 G711 calls over that link, but it will depend on your
ISP, your router and what else you're doing on the link at the time.
| Quote: | Of course, I could figure out how to configure QOS in iptables for
asterisk, it'd be a lot better.
|
A lot better to do it on your router, then it'll shape everything else on
your LAN, although you can only effectively shape outgoing traffic, but
this is usually enough given that outgoing speed is much less than
incoming. (unless your router is linux, in which case google for
wondershaper which is a good place to start)
Gordon |
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atis at iq-labs.net
Guest
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| Posted: Wed Feb 20, 2008 9:25 am Post subject: [asterisk-users] which codec over iax => pstn |
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On 2/20/08, sean darcy <seandarcy2 at gmail.com> wrote:
| Quote: | Gordon Henderson wrote:
| Quote: | On Tue, 19 Feb 2008, sean darcy wrote:
| Quote: | using asterisk(A) over iax to another asterisk server(B) which connects
to pstn over pri.
Doesn't B have translate to ulaw whatever goes out to the pstn,
|
Depends on the country, but ulaw or alaw...
|
ulaw
| Quote: |
| Quote: | so
therefore shouldn't A choose ulaw as the iax codec to B? That way
there's no loss translating from {gsm, ildc, etc} to ulaw on the B server.
|
It depends on how the call comes into A and how "bothered" A is about
doing the transcoding, or letting B do it for them.
|
the call comes into A over an analog port on a TDM400P. I assume it's ulaw.
| Quote: | If the calls come into A via GSM, then you might as well send them out
again in GSM as the call quality won't improve, but if they come into A as
G711 (ulaw or ulaw) then keep them as G711 if you don't want to lose
quality, else compress them to GSM if you don't have the bandwidth
avalable.
| Quote: | My partner thinks I'm nuts, and that gsm is much more "efficient" as the
iax codec.
|
GSM is more compressed than ulaw or alaw, so will use less bandwidth, but
in doing so, it will sound worse. (mobile phone quality rather than
landline quality)
| Quote: | BTW, we have 512kbs over the iax connection.
|
G711 needs about 80Kb/sec each way to work. (It's 64Kb/sec plus IP
overhead). GSM needs about 32Kb/sec (13Kb/sec plus IP overhead).
|
So with DSL 512kbs up and 3mbs down, plenty of room for G711.
|
Take the weakest link - up 512 kbps, that makes 6 simultenous ulaw
calls (not counting other traffic). Of course you could push more
calls, inbound voice would be good (3mbps) but outbound would be
crappy.
| Quote: | Of course, I could figure out how to configure QOS in iptables for
asterisk, it'd be a lot better.
|
If you have fixed bandwidth, it should be fairly simple, there's some
ready scripts for scheduling outbound/inbound traffic on fixed
bandwidth links. This is a very good resource for that -
http://lartc.org/
Also i found this yesterday, could be good for start. It doesn't
assume fixed bandwidth, but just gives priority to VoIP packets.
http://www.howtoforge.com/voip_qos_traffic_shaping_iproute2_asterisk
Regards,
Atis
| Quote: |
| Quote: | IAX is more efficient than SIP in packing multiple calls into the one data
stream.
| Quote: | Whom do you support?
|
My customers, and what they ask for...
|
Great. Thanks for the help.
sean
|
--
Atis Lezdins
VoIP Developer,
IQ Labs Inc.
atis at iq-labs.net
Skype: atis.lezdins
Cell Phone: +371 28806004
Work phone: +1 800 7502835 |
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seandarcy2 at gmail.com
Guest
|
| Posted: Fri Feb 22, 2008 9:28 am Post subject: [asterisk-users] which codec over iax => pstn |
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Atis Lezdins wrote:
............
| Quote: | | Quote: | | Quote: |
| Quote: | BTW, we have 512kbs over the iax connection.
|
G711 needs about 80Kb/sec each way to work. (It's 64Kb/sec plus IP
overhead). GSM needs about 32Kb/sec (13Kb/sec plus IP overhead).
|
So with DSL 512kbs up and 3mbs down, plenty of room for G711.
|
Take the weakest link - up 512 kbps, that makes 6 simultenous ulaw
calls (not counting other traffic). Of course you could push more
calls, inbound voice would be good (3mbps) but outbound would be
crappy.
| Quote: | Of course, I could figure out how to configure QOS in iptables for
asterisk, it'd be a lot better.
|
If you have fixed bandwidth, it should be fairly simple, there's some
ready scripts for scheduling outbound/inbound traffic on fixed
bandwidth links. This is a very good resource for that -
http://lartc.org/
Also i found this yesterday, could be good for start. It doesn't
assume fixed bandwidth, but just gives priority to VoIP packets.
http://www.howtoforge.com/voip_qos_traffic_shaping_iproute2_asterisk
|
That's a great find. I've never been able to figure out the lartc docs.
This really lays it out, simply. Should be linked from the digium or
voip-info sites.
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