[hylafax-users] Reducing FAX data rate

["John Matthews" <john.matthews@xxxxxxxxxxx>]

 

We are using hylafax with a VOIP PBX which results in poor quality phone lines and lots of hdlc fcs errors. We would like to try reducing the fax datarate to see if this helps reduce errors. Our modem supports V.17, V.29, V.27ter and V.21 channel 2. I notice that Hylafax always issues a +FRH=3 command to my modem. Apparently the +FRH command sets the protocol and rate. Maybe this could be used, but hylafax doesn’t seem to support changing the value provided in the +FRH command.

+FRH=n causes SoftModem to receive frames using HDLC protocol and the modulation defined below. An ERROR response code results if this command is issued while SoftModem is on-hook.

+FRH=3 V.21 channel 2 300 bps

+FRH=24 V.27 ter 2400 bps

+FRH=48 V.27 ter 4800 bps

+FRH=72 V.29 7200 bps

+FRH=96 V.29 9600 bps

+FRH=73 V.17 7200 bps (long train)

+FRH=74 V.17 7200 bps (short train)

+FRH=97 V.17 9600 bps (long train)

+FRH=98 V.17 9600 bps (long train)

+FRH=121 V.17 12000 bps (long train)

+FRH=122 V.17 12000 bps (short train)

+FRH=145 V.17 14400 bps (long train)

+FRH=146 V.17 14400 bps (short train)

 

From my hylafax session logs I see that the sending FAX modem is suggesting that we use v.17 14400bps

Apr 07 11:28:32.07: [18832]: REMOTE wants 14400 bit/s

Apr 07 11:28:32.07: [18832]: REMOTE wants A4 page width (215 mm)

Apr 07 11:28:32.07: [18832]: REMOTE wants unlimited page length

Apr 07 11:28:32.07: [18832]: REMOTE wants 3.85 line/mm

Apr 07 11:28:32.07: [18832]: REMOTE wants 2-D MMR

Apr 07 11:28:32.07: [18832]: REMOTE wants T.30 Annex A, 256-byte ECM

Apr 07 11:28:32.07: [18832]: RECV training at v.17 14400 bit/s

 

Does the receiving FAX machine have any way to negotiate say V.29 9600bps instead?

 

John Matthews

john matthews CrossML Integration Services		business communications revolution
d t m	+61 2 9020 5353 +61 2 9020 5300 +61 4 0566 1287

Australia Wide: Phone | 1300 305 110 | Fax | 1300 305 119 | Web | http://www.crossml.com

Disclaimer - April 7, 2006 This email and any files transmitted with it are confidential and intended solely for hylafax-users@xxxxxxxxxxx. If you are not the named addressee you should not disseminate, distribute, copy or alter this email. Any views or opinions presented in this email are solely those of the author and might not represent those of CrossML Pty Limited. Warning: Although CrossML Pty Limited has taken reasonable precautions to ensure no viruses are present in this email, the company cannot accept responsibility for any loss or damage arising from the use of this email or attachments.