Re: [hylafax-users] Failure to receive silence (synchronization failure)

["Alex R [MaxoTel]" <alex@xxxxxxxxxxx>]

I've had a number of people telling me that "VoIP" is the problem. Well, I'd
like to know exactly the specifics of what is the problem. "VoIP is the
problem" isn't really an answer that will help me to fix it.

I've uploaded:

SUCESS
http://119.63.202.100/faxlogs/c000000082CANON.txt
http://119.63.202.100/faxlogs/CANONFaxDSP0-dsp.raw
http://119.63.202.100/faxlogs/CANONFaxDSP0-iax.raw

FAIL (Asterisk rxfax) (We receive a lot of faxes using rxfax and generally
have very little issues with it)
http://119.63.202.100/faxlogs/c000000081INTERNAL.txt
http://119.63.202.100/faxlogs/INTERNALFaxDSP1-dsp.raw
http://119.63.202.100/faxlogs/INTERNALFaxDSP1-iax.raw

FAIL (Some other fax)
http://119.63.202.100/faxlogs/c000000083OTHER.txt
http://119.63.202.100/faxlogs/OTHERFaxDSP6-dsp.raw
http://119.63.202.100/faxlogs/OTHERFaxDSP6-iax.raw

If someone could please let me know what specifically is causing it to fail,
it would be greatly appreciated.

When I analysed the CANON files in audacity, it looks as though Hylafax was
speaking over the Canon the whole time, but somehow the Canon received it
perfectly.

Perhaps the Canon has a special ability to talk and listen at the same time?

Regards,

Alex R.


-----Original Message-----
From: hylafax-users-bounce@xxxxxxxxxxx
[mailto:hylafax-users-bounce@xxxxxxxxxxx] On Behalf Of Lee Howard
Sent: Wednesday, 16 April 2008 10:38 PM
To: Alex R [MaxoTel]
Cc: hylafax-users@xxxxxxxxxxx
Subject: Re: [hylafax-users] Failure to receive silence (synchronization
failure)

Alex R [MaxoTel] wrote:
> The VoIP server that this is on is very close to the terminations, so it
> shouldn't have anything to do with the quality or delay of the VoIP call,
>   

It doesn't have anything to do with the *delay* of the VoIP call.  It 
has everything to do with UDP being a lossy medium.

> plus I can get an identical result every time I do it (unless the VoIP
call
> to certain numbers is handled differently at the provider)
>   

I'm not sure that this is relevant.  And it's almost certain that the 
VoIP provider handles calls differently based on destination.

> A friend of mine said he had to adjust the tx/rx volume on his VoIP
switch,
> but I'm using Asterisk. Could that be the problem?

Lots of people fax over VoIP.  And lots of people have lots of trouble 
trying to fax over VoIP.  Some of them don't think that they're having 
any trouble.  Some of them just aren't paying close-enough attention to 
realize that they're having trouble faxing over VoIP but that ECM is 
rescuing them.  The end-result of trying to fax over VoIP will be quite 
variable from case to case depending on the circumstances... but unless 
you have some means to significantly mitigate the potential loss on the 
UDP connection, then you can't depend on VoIP to pass data (or fax).

Thanks,

Lee.


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