[asterisk-dev] autodetect fax on SIP channel

[Martin Vít]

Gaspar Zoltan wrote:
> Hi
>
> I used NVFaxDetect with 1.2 for SIP. This application as far as I know
> detects and decodes the fax sent in the voice channel a fax over voip
> method. 
i'm using modified version for 1.4. it playes wav as backround and it is 
possible to detect fax during play (using asterisk dsp library). It 
cannot be detected when channel are bridged.

I'm interested if it is technically possible to detect fax tone during 
bridged channesl on SIP in easy way. Any suggestions?

> T.38 is a protocol that sends fax not encoded as sound, but directly
> as digital data. For this is far more reliable.
>
> Any network jitter will cause problems for nvfaxdetect and I was unable to
> receive large faxes (more then 10 pages)with it. For small faxes it worked a
> little bit better, but sometimes still failed.
>
> Zoltan
>
> -----Original Message-----
> From: asterisk-dev-bounces at lists.digium.com
> [mailto:asterisk-dev-bounces at lists.digium.com] On Behalf Of Alexey Borisov
> Sent: Friday, July 20, 2007 9:07 AM
> To: asterisk-dev at lists.digium.com
> Subject: Re: [asterisk-dev] autodetect fax on SIP channel
>
>  >Alexey Borisov wrote:
>
>   
>>>> Hi All.
>>>> Tell me please, how-to detect fax call on SIP channel?
>>>> I found some information on voip-info about app_nv_faxdetect, but it
>>>> reffers me on newmantelecom site.
>>>> this site is not responsible anymore ;-(.
>>>> where i can take app_nv_faxdetect for asterisk 1.4? or possible any
>>>> instructions, how to make it work/
>>>>
>>>> thanks
>>>> Alex.
>>>>
>>>>         
>>   
>>
>> Hi,
>>
>> I think nv_faxdetect works to detect fax calls on ZAP (and mISDN), not SIP.
>>     
> nv >listens 
>   
>> for the fax tones, and there are no fax tones on an incoming SIP.
>> Fax over SIP is done using T.38, and I don't know how to tell it is a fax
>>     
> call >at the 
>   
>> start, i.e from the SIP INVITE.
>> Anyone?
>>     
>
>
> Really? But in man from voip-info.org ive seen, that NVFaxDetect function 
> implements fax detection just SIP and IAX channels.
> here is article -> http://www.voip-info.org/wiki-NVFaxDetect 
>
> I need it. Maybe anyone use it with aster 1.4.?
>
> Alex.
>
>
>
>
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>   


-- 
Martin Vít
LAM plus s.r.o.
http://www.lam.cz/
Tel.: 605 267 610

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