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

Simo Kivimäki simo.j.kivimaki at tut.fi
Fri Aug 12 11:13:01 CEST 2005

Ville Vehvilainen wrote:
> 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

I get about same numbers but for me the picture is perfect. Only problem
is slow tuning. From czap command to FE_HAS_LOCK it usually takes more
than 30 seconds. I had to increase timeouts to get it tune. How long it
takes for you to get tuned?

I get picture for example tuning with czap -r and:
xine stdin://mpeg2 < /dev/dvb/adapter0/dvr0

> 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.

For me the tuning is even more slower without that patch.
> I'm perfectly willing to provide any debug data I can and test any patches.

Me too.

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