[asterisk-users] spandsp (foip)

[Jay R. Ashworth]

On Mon, Sep 25, 2006 at 08:14:27PM +0800, Steve Underwood wrote:
> >Now introduce VoIP telephony... where a small amount of audio 
> >corruption (jitter) is anticipated on the UDP channel... and mix it 
> >with faxing and hopefully you can see how it just doesn't work well.  
> >VoIP is packetized audio passed over an IP network.  Packetized audio 
> >is nothing new.  ISDN circuits have had it for a long time now.  Those 
> >circuits are digital - meaning the audio waveform is digitized at 8000 
> >Hz... so the audio is represented with bytes and are packetized into 
> >frames.  Those traditional digital circuits are designed to prevent 
> >any loss of that data.  VoIP works similarly, except that the medium 
> >is lossy UDP/IP networking.
> 
> ISDN doesn't packetize voice. ISDN is a strict circuit switched TDM system.

He didn't say anything about compressed, Steve; yeah, ISDN frames the
bytes it sends.  It sends them isochronously, certainly, so jitter is
less of a problem by a couple orders of magnitude or mode, but they're
still sent in "packets".

Just not *IP* packets.

Cheers,
-- jra
-- 
Jay R. Ashworth                                                jra at baylink.com
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