[linux-dvb] or51132 QAM initialization problem

Mac Michaels wmichaels1 at earthlink.net
Mon Aug 22 05:27:57 CEST 2005


The fix is probably the same as I used on lgdt330x. There is 
an optimization that keeps track of the frequency tuned by  
the digital decoder. The digital driver does not set the 
frequency if it has not changed since it was tuned. The 
analog tuner driver knows nothing about the frequency saved 
by the digital driver. When the frequency is set using the 
video4linux code with tvtime, the hardware get changed but 
the digital driver's state does not get updated. Switch 
back to the same digital channel and the driver finds no 
change in frequency so the tuner is not reset to the 
digital frequency. The work around is to remove the check 
and always set the tuner to the specified frequency.

Attached is an untested patch:

Signed-off-by Mac Michaels <wmichaels1 at earthlink.net>

<SOAPBOX> This is an issue that I have raised previously. I 
think that the tuner driver should be shared between 
video4linux and dvb for cards of this type. The 
optimization of tuning will then work properly. I already 
have this working for the lgdt330x but some folks consider 
it bad style. </SOAPBOX>

-- Mac

On Sunday 21 August 2005 10:09 am, Michael Krufky wrote:
> Ilia Mirkin wrote:
> > I have a pcHDTV 3000 card, and it works fine with the
> > cx88-dvb and cx8800 drivers; I can receive both digital
> > and analog content. However, after switching to
> > 'analog' mode, I can't go back directly into digital
> > mode.
> >
> > If I have the QAM firmware loaded, and then go to NTSC,
> > locking onto a QAM station again does not work.
> > However, if I load up a VSB station (thus loading the
> > VSB firmware), then the lock is acquired. I can then go
> > back and reload the QAM firmware and it locks fine.
> >
> > My theory is that the cx8800 driver changes something
> > behind cx88-dvb's back (or cx88-dvb does not initialize
> > something properly upon start of a capture but does so
> > upon loading of firmware), and thus is unable to lock
> > onto the signal.
> >
> > The sequence of events is as follows, in case the
> > description above was unclear:
> >
> > azap -r qam_chan (locks)
> > tvtime (viewing works)
> > azap -r qam_chan (does not lock)
> > azap -r vsb_chan (locks)
> > azap -r qam_chan (locks)
>
> I had the same exact problem using the original lgdt3302
> driver (based on or51132) with DViCO FusionHDTV3 Gold-T. 
> It is more likely that the problem is within the or51132
> frontend driver, rather than in cx88-dvb, as this was the
> case with lgdt3302. Maybe the problem in lgdt3302 came
> from the original or51132 design?  Any ideas Mac?  Maybe
> the same type of fix can be applied?  I have cc'd Kirk
> Lapray, or51132 author.
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