Bad quality with Voxalot+IPKall
 

I have an IPKall account that redirect the call to voxalot.com.
When I receive the call the audio is not good. It's fragmented and it cut off sometimes. The caller has an quite bad reception.

When I call through Voxalot->Voipdiscount the connection is usually quite good.

What is the problem? And how do I solve it?

-Cris

Sounds to me like you might be transcoding too many times.

i.e g711 <=> g729 <=>g711

This situation can occur if you are not setting the right codec values for the provider.

For best quality try to set it up to minimise transcoding.

Thanks for the answer Martin,

IpKall gives you a standard landline phone number in the Washington district here in US for FREE.

The path is: Phone line -> IPKall -> Voxalot.com -> My phone

ipkall.com don't have a way configure the codec. At least I could not find it.
Since I can make calls without any problem (My phone->Voxalot.com->voipdiscount) I think the problem is not between Voxalot.com -> My phone. It should be between IPKall -> Voxalot.com

Any idea how to solve it?

-Cris

That's ok you don't need to change it at ipkall, you just need to make sure that the codecs you setup on the VoXaLot provider page are optimal.

Allow me to explain:

For example if ipkall supports ulaw, alaw and g729 and your phone only supported g729 and you were to put ulaw;alaw;g729 in the provider codec field, what you may find happen is:

ipkall <== ulaw ==> voxalot <== g729 ==> phone

This is the transcoding I speak of.

If however you changed your provider codec setting to just have g729, then one of these 2 pass-through scenarios are likely to happen:

ipkall <== g729 ==> voxalot <== g729 ==> phone
ipkall <== g729 ==> phone

i.e. no transcoding.

Hi Martin,
Thank you for explaining it.

My phone has these codecs in this order:
G729a
G711ulaw
G711alaw
G729
G723.1

However I don't know how to find about IPKall.
It is NOT in my Provider list.

IPKall can be configure using these options:
SIP Phone Number: XXXXXX
SIP Proxy: us.voxalot.com
Email Address: my@email.me
Password: 0000
Voice Mail on/off X Seconds to Voice Mail: 20

I had also another problem: if I didn't answer the phone the IPKall voice mail went on instead of the Voxalot one. I changed the secon to VoiceMail... this should solve this problem.

- Cris

I found this http://forum.voxilla.com/ipkall-user...29a-15456.html

They support G729a

But I am not sure what happens when IPKall pass the call to Voxalot.
It seems that depends on the coded exported by voxalot and the order of them.

Cris

For what it's worth, the last time I checked IPKall will support G729a, but only if it's the only codec on your ATA or phone's list of supported codecs. Otherwise it will choose a different codec like G711u (even if your preferred codec is G729a). I think IPKall will support some other codecs as well, but I'm not sure of the complete list.

Ok so ipkall points to your VoXaLot account and is not registered as a provider.

This is quite different then. Essentially in this scenario VoXaLot will pass it through without transcoding.

The only thing I can think off therefore is a problem with the upstream provider. Have you tried ipkall directly (without VoXaLot in the mix) to determine quality?

So If I enable only G729a codec on my phone should it work fine ?

No, I didn't. However if I don't put Voxalot I need another service. I cannot direct ipKall directly to my phone.

Any good idea about that?

-Cris

IPKall on some of its phone numbers is very bad quality. I've used the service before and the number I got assigned and started to publish ended up having all the problems you are describing, cut-off words, random noises. Beyond being generally unuseable by cutting out words every 20 seconds, it sometimes started garbling everything for a minute at a time.

It is possible deleting your current IPKall number and requesting a new one will solve the issue, though it wouldn't surprise me if it didn't.

I think they support u-law and G729, so toggling the preferred codec in your SIP device might help but that is hard to see as well in my case, where my uplink bandwidth vastly exceeds the requirements for multiple simultaneous u-law calls so there was no reason to go with G729a other than to see if it made IPKall behave better.

Ultimately I abandoned IPKall and got a number with FreeDigits ( http://www.freedigits.com/ ), which has zero quality problems and can be configured to forward to a SIP URI just like IPKall--so I just forward my number to my Voxalot account in the FreeDigits account portal.