TIPS How can I optimize FOIP?

[grzmrc]

Hi,
I'm on incrediblefax 11, but sometimes I have some issue in sending/reciving fax over SIP trunk.
What can I do to optimize FOIP?

The only thing I did was to force alaw protocol because using gsm,g722 ecc the fax stop to work.
I think that I have to disable echo cancellation, but I can't find anything in freepbx gui related to echo.

Is there anypeople that use pure FOIP that can help me?

thanks in advance

 

[wardmundy]

May work better with ULAW. Never going to be perfect. Faxing never was.

 

[Trimline2]

I use a Grandstream HT502 connected to a fax/printer without issue. As Ward says, use ULAW only and set your machine to 9600 baud, no error correction. You should be good to go.

 

[grzmrc]

I thought alaw and ulaw were equal. The only reason why I chose alaw is that I live in Europe, while ulaw should be used in the USA.

The main problem now is that I have to convert all audio files of Asterisk, in ulaw.

how can I convert all audio files including those in the subfolders?

Where can I set the baud to 9600?

Many thanks

 

[Trimline2]

Let's start with the basics. What kind of fax machine are you using and how is it connected? You are correct that alaw is for Europe.

 

[grzmrc]

I'm try to use incrediblefax 11.
avantfax <-> iaxmodem <-> hylafax <-> asterisk

 

[Trimline2]

Perhaps someone on the board who is in Europe and have this working could advise. If you Google "hylafax alaw' you'll get a lot of info.

Good luck.

 

[grzmrc]

I thought the issue rely on my connection. I had no issue with my old adsl, but now I'm using a hsdpa connection. The voip calls are very good, but it seems that faxes don't like the hsdpa even under g 711 protocol. Technically I don't know why, perhaps hsdpa uses a kind of compression that kills faxes.

 

[atsak]

I thought the issue rely on my connection. I had no issue with my old adsl, but now I'm using a hsdpa connection. The voip calls are very good, but it seems that faxes don't like the hsdpa even under g 711 protocol. Technically I don't know why, perhaps hsdpa uses a kind of compression that kills faxes.

Actually, it has to do with jitter I suspect. HSDPA connections tend to have high jitter connections; faxes are not at all tolerant of that in my experience.

 

[Chris Sweeney]

Well HSDPA would have a ton of jitter and latency can't be that great either. Even though the call quality to the human ear may be fine it wouldn't be to fax.

 

[grzmrc]

Is it possible to mitigate the problem with jitter buffer?

 

[hbonath]

I have chased FOIP to the point of it becoming my "white whale"
Jitter/Latency/etc all contribute to failing faxes. T.38 gateway is an option, however not all providers support t.38 and not all t.38 seems to be the same.

My end-all has been to go with Vitelity's vFAX platform with a vFAX enable device, which is like an ATA but essentially acts as a fax server that sits in between the fax machine and network, captures faxes as tiff files and then sends them digitally to their vFAX dialer bank.
It works so well I don't even bother with FOIP anymore.

 

[atsak]

Is it possible to mitigate the problem with jitter buffer?

No, not in my experience. Faxes don't tolerate the jitter buffers either. I can't see any wireless option working in this way. Use a digital fax service - I'm sure there's something for a few euros' a month out there, if not myfax will fax internationally at a reasonable price.

 

[Hyksos]

I'm often tempted to answer all fax related questions with things like the two posts above...
I don't because I respect people choices and possible need for plain old fax technologies...
But still I'm so glad when vfax and hosted fax gets mentioned as a good solution.

I know that plain old faxing over voip works like a charm for some people... In my experience, even plain old faxing over plain old telephone line is something I dislike highly.

With modern fax solutions, you get so much more than a working fax solution, you get backup, archival, paperless, forward possibility, access from anywhere, multiple people access, etc.

Time spent on this thread/issue by the OP more than pay for efax services, so I must conclude that when your time is worth money, plain old fax over VOIP is more than rarely a good choice.

Only 1 hour worth of my time buys more than 2 years worth of most major efax vfax solution provider services.
Just sitting down to think about using plain old fax... puts the scenario in the red compared to modern solutions.

Just my opinion and I'm sure for some there is a real need for plain old fax over VOIP, I'm thankful that I never was in such a situation.