Thank you very much for your answer Steve.

Would be FS + mod_spandsp good both for incoming and outgoing faxeds?

What could be achieved to avoid media timing issues you told? 

Regards

2011/5/9 Steve Underwood <steveu@coppice.org>

On 05/09/2011 01:16 AM, Juan Antonio Ibañez Santorum wrote:
> How much reliable FS + mod_spandsp is compared to other solutions
> (open source or not)?

The open source options are:

    Asterisk + spandsp
    Asterisk + Hylafax + iaxmodem + spandsp
    Freeswitch

These are all tested and proven to give well below 1% failures, even
with quite a lot of concurrent FAX channels in use, if things are set up
well. They can give you bad failure rates if things are not set up well.
I believe that right now you will have less trouble achieving a reliable
setup with Freeswitch. Going forward, most of my effort goes into making
the Freeswitch option the most thoroughly implemented one.

The main commercial option is:

    Asterisk + Digium's commercial FAX

Of course, there are numerous other fully commercial FAXing options
which could be used in conjunction with things like Asterisk or Freeswitch

The Digium FAX module is based on the well known Commetrex FAX engine,
which is widely deployed, and should be capable of solid results.
However, the module is more than just the core FAX engine, and some
people do have serious trouble with the module. I have helped moved
people off this, and onto Asterisk + spandsp, to improve their
reliability. In a couple of those cases people were getting quite a lot
of pages cut short when receiving FAXes with T.38, even though a
wireshark log showed a perfect exchange, from which I could correctly
decode these FAXes. The module was not reporting any errors. In a couple
of cases strange machines were sending weird things the Digium FAX
didn't cope with very well. I worked with these people to make sure
spandsp did handle the weird stuff well, and we ended up with a more
usable solution. These people told me that when they complained to
Digium they got little help. The best was an offer of a refund. Paying
to get some support didn't seem to work out too well for these people,
but I guess if the support you are looking for is mostly in getting
things configured and working on day one you might get value for money.

All these solutions require reliable signaling and reliable media
timing, and many people have setups which cannot achieve that. Most
people don't understand how things work, and will claim a solution
doesn't function for spurious reasons. For example, a number of people
say the spandsp module for Asterisk doesn't work, because they keep
getting a 488 response. That response has nothing to do with the FAX
engine. It is a negotiation error that occurs outside the FAX engine. If
they fixed their configuration the error would go away. However, many
just move on, having "proven" to themselves the solution doesn't work.

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