[asterisk-users] Still on spandsp/app_fax and T.38

Wed Feb 17 13:23:20 CST 2010

----- "Steve Underwood" <steveu at coppice.org> escreveu:

> Hi Vinícius,
> 
> Don't post big things, like wireshark traces, to a mailing list. They
> 
> are likely to ban you.
> 
> The first two calls in your wireshark log decode to the attached
> images. 
> There were no lost packets. The wireshark logs contains exactly what
> the 
> far end sent, and it was not good. The first fax page has 12 bad pixel
> 
> rows. This page was accepted, as minor defects like this are normally
> 
> accepted. The second fax starts out OK, then then just falls apart. I
> 
> think the receive modem in that gateway probably lost sync. The data 
> looks like complete rubbish beyond the part that decodes to something
> 
> sensible.
> 
> The system you are trying to interwork with seems to have serious 
> issues. It can be difficult to get providers to sort out T.38 issues,
> as 
> many of them have very little understanding of the systems they have.
> 
> Even big carriers can be very unresponsive, because they just don't
> know 
> what to do.
> 
> Regards,
> Steve
> 
> 
> On 02/18/2010 12:19 AM, Vinícius Fontes wrote:
> >> Can you try the attached version of spandsp with the T.38 gateway
> you
> >>
> >> are using? It behaves a lot more like FFA, and I want to see if
> this
> >> makes the gateway behave properly. If it does I will have to
> consider
> >>
> >> some more permanent changes to spandsp to increase its tolerance
> of
> >> yet
> >> another broken T.38 implementation. It really is depressing having
> to
> >>
> >> work around other people's broken systems like this.
> >>
> >> Steve
> >>      
> > Hi Steve. I installed the spandsp you sent me and made some tests.
> >
> > Before proceeding, it is important to share with you what I noticed
> today. Even before I installed the new spandsp lib I noticed that I
> started to receive faxes at 9600 bps, only problem being the fax won't
> get received in about 60% of the cases. I'm guessing the provider
> changed something at their side, because I don't remember changing any
> configs on Asterisk. Also important to say that it is happening to
> both app_fax and FFA now.
> >
> > Anyway, I installed the spandsp you sent me and noticed no
> difference on the behaviour. Attached to this message is a capture of
> four calls. As usual, you should only consider calls from 5433142499
> to 5421047008. There are four calls, detailed as follows:
> >
> > 1) app_fax, returned an error. Here's the CLI:
> >
> > [Feb 17 13:55:16]     -- Executing [5421047008 at entrada-e1:1]
> Goto("SIP/voxip-00000010", "interno,7008,1") in new stack
> > [Feb 17 13:55:16]     -- Goto (interno,7008,1)
> > [Feb 17 13:55:16]     -- Executing [7008 at interno:1]
> Goto("SIP/voxip-00000010", "macro-recebefax,s,1") in new stack
> > [Feb 17 13:55:16]     -- Goto (macro-recebefax,s,1)
> > [Feb 17 13:55:16]     -- Executing [s at macro-recebefax:1]
> Set("SIP/voxip-00000010", "DB(fax/count)=92") in new stack
> > [Feb 17 13:55:16]     -- Executing [s at macro-recebefax:2]
> Set("SIP/voxip-00000010", "FAXCOUNT=92") in new stack
> > [Feb 17 13:55:16]     -- Executing [s at macro-recebefax:3]
> Set("SIP/voxip-00000010", "FAXFILE=fax-92-rx") in new stack
> > [Feb 17 13:55:16]     -- Executing [s at macro-recebefax:4]
> Set("SIP/voxip-00000010", "LOCALSTATIONID=5421047008") in new stack
> > [Feb 17 13:55:16]     -- Executing [s at macro-recebefax:5]
> ReceiveFAX("SIP/voxip-00000010",
> "/var/spool/asterisk/fax/fax-92-rx.tif") in new stack
> > [Feb 17 13:56:03] WARNING[3418]: app_fax.c:128 span_message: WARNING
> T.30 Page did not end cleanly
> > [Feb 17 13:56:09] WARNING[3418]: app_fax.c:178 phase_e_handler:
> Error transmitting fax. result=40: Unexpected DCN after requested
> retransmission.
> > [Feb 17 13:56:09] WARNING[3418]: app_fax.c:767 transmit:
> Transmission failed
> > [Feb 17 13:56:09]     -- Executing [s at macro-recebefax:6]
> NoOp("SIP/voxip-00000010", "FAXSTATUS = FAILED") in new stack
> > [Feb 17 13:56:09]     -- Executing [s at macro-recebefax:7]
> NoOp("SIP/voxip-00000010", "FAXERROR = Unexpected DCN after requested
> retransmission") in new stack
> > [Feb 17 13:56:09]     -- Executing [s at macro-recebefax:8]
> NoOp("SIP/voxip-00000010", "CALLID =  5433142499 ") in new stack
> > [Feb 17 13:56:09]     -- Executing [s at macro-recebefax:9]
> NoOp("SIP/voxip-00000010", "FAXPAGES = ") in new stack
> > [Feb 17 13:56:09]     -- Executing [s at macro-recebefax:10]
> NoOp("SIP/voxip-00000010", "FAXBITRATE = ") in new stack
> > [Feb 17 13:56:09]     -- Executing [s at macro-recebefax:11]
> NoOp("SIP/voxip-00000010", "FAXRESOLUTION = ") in new stack
> > [Feb 17 13:56:09]     -- Executing [s at macro-recebefax:12]
> NoOp("SIP/voxip-00000010", "FAXMODE = T38") in new stack
> > [Feb 17 13:56:09]     -- Executing [s at macro-recebefax:13]
> Hangup("SIP/voxip-00000010", "") in new stack
> > [Feb 17 13:56:09]   == Spawn extension (macro-recebefax, s, 13)
> exited non-zero on 'SIP/voxip-00000010'
> >
> > 2) app_fax, received the fax succesfully. No configs changed.
> >
> > 3) FFA, error. All I did in order to use FFA was this:
> >
> > module unload app_fax.so
> > module load res_fax.so
> > module load res_fax_digium.so
> >
> > Here's the CLI when the error happened:
> >
> > [Feb 17 13:56:35]     -- Executing [5421047008 at entrada-e1:1]
> Goto("SIP/voxip-00000019", "interno,7008,1") in new stack
> > [Feb 17 13:56:35]     -- Goto (interno,7008,1)
> > [Feb 17 13:56:35]     -- Executing [7008 at interno:1]
> Goto("SIP/voxip-00000019", "macro-recebefax,s,1") in new stack
> > [Feb 17 13:56:35]     -- Goto (macro-recebefax,s,1)
> > [Feb 17 13:56:35]     -- Executing [s at macro-recebefax:1]
> Set("SIP/voxip-00000019", "DB(fax/count)=93") in new stack
> > [Feb 17 13:56:35]     -- Executing [s at macro-recebefax:2]
> Set("SIP/voxip-00000019", "FAXCOUNT=93") in new stack
> > [Feb 17 13:56:35]     -- Executing [s at macro-recebefax:3]
> Set("SIP/voxip-00000019", "FAXFILE=fax-93-rx") in new stack
> > [Feb 17 13:56:35]     -- Executing [s at macro-recebefax:4]
> Set("SIP/voxip-00000019", "LOCALSTATIONID=5421047008") in new stack
> > [Feb 17 13:56:35]     -- Executing [s at macro-recebefax:5]
> ReceiveFAX("SIP/voxip-00000019",
> "/var/spool/asterisk/fax/fax-93-rx.tif") in new stack
> > [Feb 17 13:56:35]     -- Channel 'SIP/voxip-00000019' receiving FAX
> '/var/spool/asterisk/fax/fax-93-rx.tif'
> > [Feb 17 13:56:35] NOTICE[3435]: res_fax.c:712 generic_fax_exec:
> Negotiating T.38 for receive on SIP/voxip-00000019
> > [Feb 17 13:56:35] NOTICE[3435]: res_fax.c:779 generic_fax_exec:
> Negotiated T.38 for receive on SIP/voxip-00000019
> > [Feb 17 13:56:35]     -- Channel 'SIP/voxip-00000019' FAX session
> '0' started
> > [Feb 17 13:57:26]     -- FAX handle 0: [ 051.075619 ], entering
> CLOSING state
> > [Feb 17 13:57:26]     -- FAX handle 0: [ 051.165605 ], entering
> CLOSING state
> > [Feb 17 13:57:29]     -- Channel 'SIP/voxip-00000019' FAX session
> '0' is complete, result: 'FAILED' (FAX_FAILURE_PARTIAL), error:
> 'NO_ERROR', pages: 1, resolution: '204x98', transfer rate: '9600',
> remoteSID: '5421047010'
> > [Feb 17 13:57:29]     -- Executing [s at macro-recebefax:6]
> NoOp("SIP/voxip-00000019", "FAXSTATUS = FAILED") in new stack
> > [Feb 17 13:57:29]     -- Executing [s at macro-recebefax:7]
> NoOp("SIP/voxip-00000019", "FAXERROR = NO_ERROR") in new stack
> > [Feb 17 13:57:29]     -- Executing [s at macro-recebefax:8]
> NoOp("SIP/voxip-00000019", "CALLID =  5433142499 5421047010") in new
> stack
> > [Feb 17 13:57:29]     -- Executing [s at macro-recebefax:9]
> NoOp("SIP/voxip-00000019", "FAXPAGES = 1") in new stack
> > [Feb 17 13:57:29]     -- Executing [s at macro-recebefax:10]
> NoOp("SIP/voxip-00000019", "FAXBITRATE = 9600") in new stack
> > [Feb 17 13:57:29]     -- Executing [s at macro-recebefax:11]
> NoOp("SIP/voxip-00000019", "FAXRESOLUTION = 204x98") in new stack
> > [Feb 17 13:57:29]     -- Executing [s at macro-recebefax:12]
> NoOp("SIP/voxip-00000019", "FAXMODE = ") in new stack
> > [Feb 17 13:57:29]     -- Executing [s at macro-recebefax:13]
> Hangup("SIP/voxip-00000019", "") in new stack
> > [Feb 17 13:57:29]   == Spawn extension (macro-recebefax, s, 13)
> exited non-zero on 'SIP/voxip-00000019'
> >
> > 4) FFA, received successfully. Again, no change in any configs.
> >
> >
> > That provider delivers a 2mbps SHDSL modem connected to a Cisco 1841
> router with 2 ethernet interfaces. On the first one it's the SIP DID
> dedicated service, capped to 1mbps and 15 simultaneous calls. On the
> other port there is a business grade Internet access, also capped to
> 1mbps. The only thing that changed form last week is that I started to
> use that Internet link, but it should not interfere because the
> provider configures QoS on both ends. I unfortunely don't understand
> the T38 protocol enough to tell if there's packet loss or something
> just looking at the capture. Could you take a look at that please? I
> think that might be the cause of the sudden unreliability.
> >
> >