[asterisk-users] MagicJack quality

[Anthony Francis]

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.
>
> If Magic-jack sounds impressively clear, a wideband codec would be my guess.
>
> Regards,
> Steve
>
>   
Like I said, Speex. It features Narrowband (8 kHz), wideband (16 kHz), 
and ultra-wideband (32 kHz) compression in the same bitstream.