[linux-dvb] Re: New Nova-T errors

["Edward Wildgoose" <Ed@Wildgooses.com>]

> From: "Edward Wildgoose" <Ed@Wildgooses.com>
> > I have now got a new Nova-T to replace my full featured card, but
> > unfortunately I'm getting a pretty scrambled picture which is
> > "recognizable" as the original channel, but has huge multicoloured
> > mpeg chunks all over it and lots of frame skipping (and big sound
> > breakup) on most channels, and a big lag in sound on the few channels
> > that the picture is OK.
>
> Maybe your old full-featured card wasn't the problem after all, but your
> signal ;)

Hmm, well the full featured card gets practically zero BER rates, the
standalone receiver on my TV reports good signal, and the windows driver is
reporting something like 100% signal and 80% quality (whatever that means).
The windows driver also runs this card perfectly.

You could be right, but circumstantially I think that this is not a signal
quality issue (and I'm also fairly close to the huge crystal palace
transmitter with a good roof antenna).

> > The Nova-T may be one of the newer designs and includes a remote control
> > in the box.  The chips appear to be: Philips TDA10045H and Philips
> TDM1316L
>
> Except for the remote control this seems to be the card that Andrew has
> developed the TDA1004x frontend driver on it...

Sounds promising.  Any idea how it got into the DVB drivers?  I thought it
was dvb-kernel only (just want to make sure that I'm not doing something
wrong...)

> > and I find that I need to use the tda1004x AND the ves1820 frontends
> > to make it work
>
> Humm, really? The VES1820 frontend really should not be needed.

Yep, if you don't load the ves1820 module then /dev/dvb/adaptor0 appear, but
there is no "frontend0" device created.  Everything else is in there
though... Very strange...

> > Can anyone please shine a little light on this!  I *suspect* that tuning
> > is failing, for example the exact freq in Hz for BBC one is something
> > like 505833330, but I have to enter this in dvbstream as "-f 505833",
and
> > I have an idea that this is not close enough for a good lock.
>
> You have the wrong idea ;) The frontend module is using the 1/6th MHz step
> size, and as such, 505833kHz ends up as being exactly 50583333.333 kHz
> (plus oscillator offset) being programmed into the tuner PLL.

Hmm, where in the code would I be looking to change this?  Thanks for the
hint though

>
> > The reason for the suspicion is that dvbtune is reporting fairly high
> > error rates, and dvbstream just gives a single number, but it is in
> > the 500 range.  Does this sound plausible?
>
> It seems you simply have a weak signal. While you might try fiddling the
> the frontend driver (Andrew used what ends up as a 36.166667 MHz
oscillator
> offset like the TechnoTrend driver does, which the DVB IF amplifier
> downconverts to 5.166667 MHz, which is 166.667kHz off its centre
frequency,
> while I proposed using a 36 MHz oscillator offset, which would be
> downconverted to 5 MHz, running the DVB IF amplifier right on centre, but
> the tuner 130kHz off-centre), this may only make a marginal difference -
> what you should really be looking into is improving the quality of the
> signal you feed into the card...!

Well, it could be, but I tried the full featured card in again with an
indoor antenna, and this gave me a good look at what a poor quality signal
is like.  And as I said the windows driver is reporting signal strengths
right up at the top of the bar.  Picture quality is perfect with the windows
driver, and with the full featured card (and this card reports a strong
signal as well).  The hardware decoder box on the TV also says that I have a
strong signal.

You are right that this DOES look like a signal strength issue though, so if
we can assume that there is a strong signal on the antenna cable, and that
the windows driver can run the card and receive it ok, then this seems to me
to suggest that it looks like a *tuning* issue with the current driver/card?
ie the signal is there, but I'm not quite receiving it.  Does this sound
about right?  (I'm skipping the possbilities like corruption on the pci bus,
etc)

Can you (or anyone) please confirm whether tzap should work with this card.
If it should, then I guess I have another issue anyway (since mine reports
an error and stops.)  It would be nice if it did because I could then get
the tuning strength out of it, and whether it locked properly or not.

Thanks for ANY hints on where to go next!

Ed W



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