[Asterisk-Users] HylaFAX v. spandsp

[Michael Welter]

Thanks for all your efforts, Steve.

Because I'm unable to configure multiple PCI modem cards on the fax 
server, I'll have to give spandsp a go.

Never a dull moment around here.

Mike

Steve Underwood wrote:
> Michael Welter wrote:
> 
>> Can someone explain where we are with spandsp?  Is it ready for a 
>> production environment?  How much will one fax using spandsp load the 
>> processor on an * system?
>>
>> Thanks,
>> Mike
> 
> 
> Some people have been using spandsp-0.0.1k in production systems for 
> months. The main problems have been:
> 
>    Canon fax machines often gave problems
>    HP machines are buggy, and with spandsp the bugs cause black streaks 
> oon received documents.
>    People get pages chopped in half.
> 
> You won't really notice the load caused by one channel of spandsp's fax 
> machine on most modern CPUs. I had 100 channels running on a dual Xeon 
> at one point, but I haven't tested recent versions at high loads.
> 
> With the latest spandsp-0.0.2pre4
>    The bug affecting Canons seems to be resolved.
>    The software used to rely on the internals of libtiff to compress and 
> decompress images. Now it uses its own code which works around buggy 
> machines likes the HPs, and allows better reporting of the received data 
> quality.
>    Of all the pages getting chopped problems I received, one turned out 
> to be a stability issue in the modems. This seems to be resoolved.
> 
> Every other report of pages getting chopped, that I have investigated, 
> has been due to timing problems in * or the hardware. This is probably 
> about 30 examples now. There is nothing I can do about this. If spandsp 
> does not work in these cases, neither will hardware modems and HylaFAX 
> with the calls passing through *. Modems just cannot tolerate hiccups in 
> the audio stream.
> 
> The long delay between spandsp-0.0.1k and the recent spandsp-0.0.2prexxx 
> versions has been due to the fact that spandsp-0.0.1k has been working 
> pretty well for a lot of people. There wasn't a need for many minor 
> releases. 0.0.2 is a fairly major update, with many areas of the 
> software changing in major ways. Some of these are complete, and some 
> are still works in progress.
> 
> The modems have been reworked to get closer to the theoretically 
> achievable performance on noisy lines. Their compute requirements are 
> also a bit lower now.
> 
> Fax compression and decompression has been added.
> 
> An incomplete skeleton for class 1 modem operation, to work with 
> HylaFAX, has been added.
> 
> A nearly working V.17 modem has been added. This still needs 
> improvements to the receiver carrier locking to make it work properly.
> 
> A half finished V.22bis modem has been added. A couple of people asked 
> for this, so allow integration of things like credit card validation 
> machines with *. Most of these still sues V.22bis.
> 
> Variable speed playback of speech files. This is something a lot of 
> people ask for, but which is fairly useless in practice :-). Its just to 
> play with, though.
> 
> A number of little modules, such as V.8 processing, have been 
> implemented, tested, and added to spandsp, but are not really being used 
> right now.
> 
> Regards,
> Steve
> 
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-- 
Michael Welter
Introspect Telephony Corp.
Denver, Colorado US
+1.303.674.2575
mike at introspect.com
www.introspect.com