[linux-dvb] Tuning problems with TT DVB-C 1500 (saa7146 + stv0297) and QAM128

Ville Vehvilainen vvehvilainen at gmail.com
Thu Aug 11 17:45:44 CEST 2005


Hi,

I'm unable to get any data out of a new TechnoTrend C1500 budget card
(SAA7146 w/
STV0297). While it seems to successfully tune, czap reports a
suspicuously low s/n ratio
(around 3000-4000 decimal, compared to a older C1.0 budget card which
works fine and
gets around 60000). And no video, audio, or anything else comes out.
The "scan" utility
won't find any services either.

Here's a sample czap output: 

~> czap -r -c channels.conf MTV3
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
reading channels from file '.mplayer/channels.conf'
 15 MTV3:346000000:INVERSION_AUTO:6900000:FEC_NONE:QAM_128:305:561:49
 15 MTV3: f 346000000, s 6900000, i 2, fec 0, qam 4, v 0x131, a 0x231
status 1f | signal 033a | snr 0ee2 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
status 1f | signal 0339 | snr 0dea | ber 00000000 | unc 00000000 | FE_HAS_LOCK

etc.

And for the older C1.0 card:

~> czap -r -c channels.conf MTV3
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
 15 MTV3:346000000:INVERSION_AUTO:6900000:FEC_NONE:QAM_128:305:561:49
 15 MTV3: f 346000000, s 6900000, i 2, fec 0, qam 4, v 0x131, a 0x231
status 00 | signal b1b1 | snr c6c6 | ber 009ffff6 | unc ffffffff | 
status 1f | signal ffff | snr eded | ber 009ffff6 | unc ffffffff | FE_HAS_LOCK
status 1f | signal ffff | snr ebeb | ber 009ffff6 | unc 00000000 | FE_HAS_LOCK


I understand that this card has had problems with the current drivers
tuning to QAM128
channels, which this is, as can be seen from the output. All channels
I can test on are
QAM128 so I can't say whether the problems relate to that.

This is on Linux 2.6.13-rc6 and dvb-kernel CVS checkout from Monday. The same 
behaviour occurs whether or not I patch the stv0297 driver to disable
corner detection for
QAM128, as described a couple of weeks ago on this list.

I'm perfectly willing to provide any debug data I can and test any patches.

Thanks,

Ville Vehviläinen




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