[asterisk-users] MagicJack and Skype call quality

[Jason Aarons (US)]

My understanding is Skype's secret is using the iLBC codec, which Cisco
has also licensed for their 79X2 models as well.  I travel and lot and
in places where Yahoo Phone Out or MSN Phone or Cisco IP Communicator
will fail the Skype client will work.  The iLBC codec can really handle
packet loss.

Skype High Quality Video with the Logitech Orbit AF on both ends is
awesome. I got my family a set for Fathers day. Just amazing video
quality. Uses a On2 VP-7 codec that has much lower cpu and other
benefits over h.264.



-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Steve
Underwood
Sent: Saturday, July 12, 2008 3:30 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] MagicJack quality

Tzafrir Cohen wrote:
> On Sat, Jul 12, 2008 at 10:26:24AM +0800, Steve Underwood wrote:
>   
>> C. Savinovich wrote:
>>     
>>> I am puzzled by the quality of magicjack.  I keep trying to figure
out how
>>> they can the quality be that adequate.  Since Skype also has an
excellent
>>> quality, that leaves me to believe that software based calls
(softphones)
>>> could have and advantage over hardphones, provided there is a
parameter that
>>> those 2 companies are addressing.
>>>
>>> Anyone's thoughts on this?
>>>
>>> CS
>>>   
>>>       
>> I don't know what Magic-jack does (I've never actually seen one), but
I 
>> know the key thing about Skype that impresses people - its wideband 
>> voice codec. A lot of people poo-poo the idea that wideband voice has

>> value in a phone call. They are either close to deaf, or have never 
>> tried it. Clarity is profoundly improved. Skype seems to use various 
>> tricks to keep the packet flow smooth, but its wideband that makes it

>> sound better than the PSTN.
>>
>> You might think a standard phone plugged into an adaptor, like a 
>> Magic-jack, would be limited to narrow band voice, as that is all the

>> phone was designed for. It turns out most phones only aggressively 
>> filter at the low end of the band. They let a lot of energy above
4kHz 
>> through, and they do generally sound better through a wideband codec.
>>
>> Many modern line interface chips are actually capable of running in a

>> 16k samples/second mode, even though most are programmed for 8k 
>> samples/second. I think the ones on the TDM400P type cards can. Some 
>> from Silicon Labs certainly can, and chips from Zarlink and others
can.
>>     
>
> The DAA in those cards can work in 16Hz. So they can send higher
quality
> samples to the telco. Provided Zaptel supports it. But then again, it
> will get lost as soon as it gets converted to digital at the telco,
> right?
>   
I guess I wasn't clear. What I said was only useful for a SLIC to phone 
connection. It won't be of any benefit for a DAA to PSTN exchange 
connection, for the reason you state.
> Anyway, the ProSLIC chip does not seem to support it. 
>   
Silicon Labs make a Wideband ProSLIC, Si 3216, which is, er, wideband. 
As I said before, Zarlink and other make them too.

Regards,
Steve



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