[linux-dvb] Re: Scan cannot cope with new Australian channel?

[Nigel Pearson <nigel@ind.tansu.com.au>]

On Jan 29, 2004, at 3:29 PM, John Dalgliesh wrote:
> Yeah that Digital 4 channel sure has some weird setup. And half the
> services that it reckons are running are actually not running.
	I think they are running, but without any audio data.

...
> > 	Adding -v does nothing helpful. Any ideas?
> Have a look at the code in scan to see what it does if the service name
> doesn't get set, but the network name does (or maybe the other way
> around).
	It was actually something stranger than that.
parse_nit() calls parse_descriptors() twice, first with
a NULL data pointer, and next with a transponder.

	It seems that the first time, it looped up to
a descriptor tag of 0x5a, and was then calling
parse_terrestrial_delivery_system_descriptor(),
but because the transponder data is NULL, it was
crashing.

	I guess that, ideally, we would tell the station to
fix their descriptor data, but in the meantime here is
a robustness patch:

% sudo scan dvb-tuning.uhf
scanning dvb-tuning.uhf
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
Frontend can not do INVERSION_AUTO, trying INVERSION_OFF instead
initial transponder 578500000 1 2 0 3 1 2 0
>>> tune to:  
578500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_NONE:QAM_64: 
TRANSMISSION_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE
Network Name 'DIGITAL FOUR'
Segmentation fault

% diff -u scan.c scan.c.new
--- scan.c      Mon Feb  2 10:05:24 2004
+++ scan.c.new  Mon Feb  2 10:07:29 2004
@@ -625,6 +625,10 @@
                        break;

                case 0x5a:
+                       if (!data) {
+                               warning("Cannot parse system descriptor  
(NULL data)\n");
+                               break;
+                       }
                        if (t == NIT)
                                 
parse_terrestrial_delivery_system_descriptor (buf, data);
                        break;

% sudo ./scan.new dvb-tuning.uhf
scanning dvb-tuning.uhf
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
Frontend can not do INVERSION_AUTO, trying INVERSION_OFF instead
initial transponder 578500000 1 2 0 3 1 2 0
>>> tune to:  
578500000:INVERSION_OFF:BANDWIDTH_7_MHZ:FEC_2_3:FEC_NONE:QAM_64: 
TRANSMISSION
_MODE_8K:GUARD_INTERVAL_1_8:HIERARCHY_NONE
Network Name 'DIGITAL FOUR'
WARNING: Cannot parse system descriptor (NULL data)
0x0000 0x0028: pmt_pid 0x010c (null) -- D-FOUR (running)
0x0000 0x0029: pmt_pid 0x0101 ABC -- D4-News (running)
0x0000 0x002c: pmt_pid 0x010d (null) -- D-FOUR. (running)
0x0000 0x002d: pmt_pid 0x0102 OICT -- D4-NSW (running)
0x0000 0x0030: pmt_pid 0x0103 TAB -- D4-TAB (running)
0x0000 0x0031: pmt_pid 0x0104 EXPO/TVSN -- D4-EXPO (running)
0x0000 0x0191: pmt_pid 0x0105 Fed Parliament -- D4Parl-Reps (running)
0x0000 0x0192: pmt_pid 0x0106 Fed Parliament -- D4Parl-Senate (running)
0x0000 0x0193: pmt_pid 0x0107 Fed Parliament -- D4Parl-ComReps (running)
0x0000 0x0194: pmt_pid 0x0108 Fed Parliament -- D4Parl-1Com'tee  
(running)
0x0000 0x0195: pmt_pid 0x0109 Fed Parliament -- D4Parl-2Com'tee  
(running)
0x0000 0x0196: pmt_pid 0x010a Fed Parliament -- D4Parl-3Com'tee  
(running)
0x0000 0x0197: pmt_pid 0x010b Fed Parliament -- D4-Parl-1Com'tee  
(running)
dumping lists (13 services)
...

--
Nigel Pearson, nigel@ind.tansu.com.au | "Reality is that which,
Telstra BI&D, Sydney, Australia       |  when you stop believing
Office: 8255 4222    Fax:  8255 3153  |  in it, doesn't go away."
Mobile: 0408 664435  Home: 9792 6998  |  Philip K. Dick - 'Valis'



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