Re: [hylafax-users] Unreliable fax services via VoIP connection

[Uwe Maier <umaier@xxxxxx>]

Hi Andrew,
I had to substitute a pots wire for a short distance with VOIP over WLAN.
I worked fine using the 711 codecs but failed without them. AFAIK VOIP providers tend to cut down on bandwidth by using "better" codecs (surely they provide better quality for voice).

Lucas didn't mention any distance (neither physical nor net hops) - but I can assure you - even if he has a perfect line (small latency and low jitter) he'll fail just by using the wrong codecs.

Regards,
uwe

andrew rinaldi wrote:

Uwe.

If you read Lee's post you will understand why VoIP will be unreliable for
fax.  Changing to an alternative Codec will have no bearing if you are using
a UDP/IP network (the 'internet').  We did a lot of testing of fax over VoIP
in both the UK and USA with very poor results.  I will try to get these
results published on our website.

Interestingly, we found that T.38 over a true IP connection is also
unreliable when compared to T.38 over PSTN.

Regards

ANDREW RINALDI
Mainpine Ltd. Support
USA +1 718 701 2422 | Asia/Europe +44 1225 436137 
andrew.rinaldi@xxxxxxxxxxxx | www.mainpine.com 

-----Original Message-----
From: hylafax-users-bounce@xxxxxxxxxxx
[mailto:hylafax-users-bounce@xxxxxxxxxxx] On Behalf Of Uwe Maier
Sent: 06 March 2006 13:30
Cc: hylafax-users@xxxxxxxxxxx
Subject: Re: [hylafax-users] Unreliable fax services via VoIP connection

Geoffrey wrote:

  

Darrick Hartman wrote:

    

Lucas Barbuto wrote:

      

Hi all,

My office is connected to the public phone network via a virtual PRI 
through our VoIP provider. I have two external modems connected to 
analogue ports on our PBX, both are used by Hylafax to receive 
incoming faxes. The software works exceptionally well in converting 
and dispatching messages, however, we have a lot of trouble 
receiving faxes.
        

VoIP is not ready for use with faxing.  Do not use it.  Get an analog 
line for fax.
      

I would guess it would depend on your personal experience.  I used my 
voip for faxing all the time, never a problem.  Certainly it would 
depend on the bandwidth you have available and how busy your network is.

    

Probably it depends on the codec you use: there are lossless and the others.

If there is a way to change to G711u or G711a (lossless 64kbit/s codecs) I
would give it another try.

Regards,
uwe

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