Johann Steinwendtner wrote:
> Ray Jackson schrieb:
>   
>> Luki wrote:
>>
>>     
>>>> However, when I execute
>>>> TxFax I see two g711 alaw packets going out for every one coming back, so 
>>>> my
>>>> outbound throughput is around 160kbps now.  The second packet's payload
>>>> looks similar to the first, almost like a duplicate.
>>>>    
>>>>
>>>>         
>>> I'm no expert, but I think that's the redundancy intrinsic to T.38.
>>> Steve Underwood had a page on T.38 but it's gone... Google's cache:
>>> http://72.14.253.104/search?q=cache:6vjemQ-5rCsJ:www.soft-switch.org/t38/ch02.html
>>>  
>>>
>>>       
>> I am far from an expert myself, but from my understanding the fax 
>> conversation starts out as standard RTP voice traffic (G711) and then 
>> switches to T.38 when the receiving gateway (usually) detects a fax tone 
>> - at least, this is the way the Cisco 5400's seem to operate.  However, 
>> my issue is that I am never actually switching over to T.38/UDPTL 
>> transmission as the fax tone itself is not recognised and is coming 
>> through as garbage to the other fax machine.  I was wondering if it was 
>> possibly related to the 2 x alaw packets being sent where I would 
>> usually expect to see just 1?  If there is some redundancy also built 
>> into the initial RTP G711 conversation, I'm wondering if this can be 
>> disabled somehow in the SpanDSP or OPBX code/config?
>>
>>     
>
> I 've met the same issue (see also Bug #279).
>
> Best regards
>
> Hans
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>
>   

I think I've found the  SIPT38switchover application to be unreliable too.
Alex
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