Re: [hylafax-users] Confusion about ECM and Multitech

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

A. Kalten wrote:

> With HylaFax 4.3.1 I am using a Multitech 5634ZPX, which, 
> according to the technical manual, fully supports the Error
> Correction Mode (ECM).
>
> However, when HylaFax is started (class 2.1), I see this in
> the log file:
>
> FaxGetty[1318]: MODEM Supports no ECM
> FaxGetty[1318]: MODEM Supports T.30 Annex A, 64-byte ECM
> FaxGetty[1318]: MODEM Supports T.30 Annex A, 256-byte ECM
>  

The log message there is a bit misleading.  The first line makes it 
sound like the modem doesn't support ECM and the next two lines seem to 
contradict the first.

What that first line really means is that the modem supports non-ECM 
mode faxing (in addition to T.30-A 64-bit and 256-bit ECM modes).  That 
the modem supports non-ECM mode may be a kind of no-brainer and one may 
ask why bother stating it in the logs, then; the answer is because what 
is really happening there is the logging is indicating that the Class 
driver correctly set up the modem internally.

That logging there isn't so much supposed to be used to tell us what the 
modem supports - because, for example, it doesn't show anything about 
the Class 2.1 JPEG support that the modem has - but rather, the purpose 
there is for the person troubleshooting to be able to identify any error 
in the driver setup.

> Also, when sending a fax (class 2.1), the log does not explicitly
> state that ECM is being used:
>
> Jan 02 08:42:55.13: [  971]: REMOTE best rate 31200 bit/s
> Jan 02 08:42:55.13: [  971]: REMOTE max A4 page width (215 mm)
> Jan 02 08:42:55.13: [  971]: REMOTE max unlimited page length
> Jan 02 08:42:55.13: [  971]: REMOTE best vres 15.4 line/mm
> Jan 02 08:42:55.13: [  971]: REMOTE format support: MH, MMR
> Jan 02 08:42:55.13: [  971]: REMOTE supports T.30 Annex A, 256-byte ECM
> Jan 02 08:42:55.13: [  971]: REMOTE best 10 ms/scanline
> Jan 02 08:42:55.13: [  971]: USE 31200 bit/s
> Jan 02 08:42:55.13: [  971]: SEND file "docq/doc1.tif;71"
> Jan 02 08:42:55.13: [  971]: USE A4 page width (215 mm)
> Jan 02 08:42:55.13: [  971]: USE unlimited page length
> Jan 02 08:42:55.13: [  971]: USE 7.7 line/mm
> Jan 02 08:42:55.13: [  971]: USE 1-D MH
> Jan 02 08:42:55.13: [  971]: USE 10 ms/scanline
>
> There is no problem, but just to satisfy my curiosity, why
> does the log indicate "Supports no ECM" and are the faxes
> being sent using ECM?

Please send this whole log.  In this case it appears that the receiver 
supports ECM but that either the admin or the user disabled the usage of 
ECM, at least for this job.

Lee.


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