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Re: [hylafax-users] faxgetty flailing and failing.



On 2005.01.11 09:31 Jean-Pierre Radley wrote:

Jan 11 12:20:35.46: [11449]: RECV training at v.17 14400 bit/s
Jan 11 12:20:35.49: [11449]: <-- [11:AT+FRM=145\r]
Jan 11 12:20:37.04: [11449]: --> [7:CONNECT]
Jan 11 12:20:38.10: [11449]: RECV: TCF 1804 bytes, 5% non-zero, 1699
zero-run
Jan 11 12:20:38.10: [11449]: RECV: reject TCF (zero run too short, min
1800)

At 14400 baud you need 1800 bytes to produce 1 sec, which if the "minimum" duration that HylaFAX is expecting a good TCF signal to last. That's not happening, so it looks like the modem is slow to detect the data carrier and that the line is noisy.


Jan 11 12:20:44.19: [11449]: RECV training at v.29 9600 bit/s
Jan 11 12:20:44.22: [11449]: <-- [10:AT+FRM=96\r]
Jan 11 12:20:44.64: [11449]: --> [7:CONNECT]
Jan 11 12:20:46.27: [11449]: RECV: TCF 1890 bytes, 4% non-zero, 1801
zero-run

1801 bytes at 9600 baud is 1.5 seconds, which indicates that you got a perfectly clear connection with V.29. This may suggest that there is some problem with V.17 over this connection.


Jan 11 12:20:46.27: [11449]: --> [10:NO CARRIER]
Jan 11 12:20:46.27: [11449]: DELAY 75 ms
Jan 11 12:20:46.35: [11449]: TRAINING succeeded
Jan 11 12:20:46.35: [11449]: ACCEPT TSI "SSC Consolidation"
Jan 11 12:20:46.35: [11449]: <-- [9:AT+FTH=3\r]
Jan 11 12:20:46.40: [11449]: --> [7:CONNECT]
Jan 11 12:20:47.70: [11449]: --> [2:OK]

The CFR signal is transmitted. Now we are going to wait for the high-speed data carrier to receive the fax image...


Jan 11 12:20:47.73: [11449]: <-- [10:AT+FRM=96\r]
Jan 11 12:20:50.67: [11449]: --> [8:+FCERROR]
Jan 11 12:20:50.67: [11449]: <-- [10:AT+FRM=96\r]
Jan 11 12:20:51.06: [11449]: --> [8:+FCERROR]
Jan 11 12:20:51.06: [11449]: <-- [10:AT+FRM=96\r]
Jan 11 12:20:51.45: [11449]: --> [8:+FCERROR]
Jan 11 12:20:51.45: [11449]: <-- [10:AT+FRM=96\r]
Jan 11 12:20:58.60: [11449]: --> [2:OK]

What this indicates is that when the modem went to look for the V.29 9600 baud carrier it found some other carrier there, probably V.21 (the carrier used to send the slow-speed messages). There are a few different things that we could do at this point: 1) if the modem supported it and if HylaFAX supported it we could use the +FAR command to automatically adjust to receive whatever data the sender is transmitting at that point, unfortunately, most modems don't support +FAR, and currently HylaFAX doesn't, either; 2) we can just repeat AT+FRM=n until we get bored or until we get something other than +FCERROR; 3) we can assume that V.21 is being used and try listening for V.21 to see what it is that the sender is trying to tell us.


In my tests I found that #2 was usually a better approach than #3 because usually the reason for +FCERROR is due to "mishaps" between the sender's and the receiver's modulators - such as "clicks" or "noise" in the raising and lowering of carriers. However, in cases where the sender doesn't receive the CFR signal properly, it will likely transmit CRP, and this would also cause the same problem, and #3 would be a better choice. However, in my tests I found that the likelihood of this proving to be beneficial was much less than when using #2.

If your modem supported +FAR (#1) then it may be a really nice thing to get it supported in HylaFAX. I have some modems that do support +FAR, but this kind of scenario (where +FAR would be useful) plays out so infrequently for me that I haven't been able to justify the development cost to myself.

All of that said... the period after TCF is especially problematic for various reasons. For this purpose we have the Class1MsgRecvHackCmd, paralleling Class1TCFRecvHack in some ways, which allows you to interject a command or a pause before raising the high-speed data reception carrier. If this kind of error happens with all incoming faxes, then you may want to play with settings like: "Class1MsgRecvHackCmd: AT+FRS=1".

Lee.

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