[Asterisk-Users] V.17

[Steve Underwood]

Tamas Jalsovszky wrote:

>Steve Underwood wrote:
>
>  
>
>>Tamas J wrote:
>>
>>    
>>
>>>Hello,
>>>
>>>I have seen that SpanDSP supports V.17 faxing, however when I tryed to
>>>send pages, I eneded with very ugly pages (unreadable). Did anybody else
>>>try that?
>>>Yes, I checked frame slips and clocking on PRI, everything has to be OK.
>>>
>>>Regards,
>>>    Tamas
>>> 
>>>
>>>      
>>>
>>V.17 is disabled in spandsp. There is a reason for that.
>>
>>Regards,
>>Steve
>>    
>>
>
>What is that reason? ;)
>How much work is needed to have v.17 working? Yes, depends on who makes
>the work ;) Do you think a newbie in fax protocols can make it in
>reasonable time?
>  
>
Being a fax protocol newbie is no problem at all. Being a DSP newbie 
might be. :-)

The missing bit is making the V.17 modem's carrier and symbol sync crisp 
enough to acquire the signal on the short training sequence. I think 
everything else is basically in place. Of course, it needs extensive 
testing once the missing piece is in place. I haven't touched that modem 
code for ages, as it hasn't bubbled up the priority list enough.

IBM had a patent related to the trellis coding in V.17, but I think that 
has expired. As far as I know there are no longer patent issues with 
V.17. If someone knows otherwise, please tell me. V.17 is basically one 
half of V.32bis, so the patent issues should be similar.

Regards,
Steve