[pvrusb2] Two PVR USB2 unit initially tune PAL as black and white

[Tom Warren]

On 20 June 2011 00:13, Mike Isely <isely at isely.net> wrote:

> On Mon, 13 Jun 2011, Tom Warren wrote:
>
> > On 4 May 2011 13:17, Tom Warren <psycadillac at gmail.com> wrote:
> > >
> > > Greetings,
> > >
> > > I have two WinTV PVR USB boxes I'm using with the pvrusb2 driver which
> feed into tvheadend playing PAL cable channels. The set up works but I
> always get the first tuned channel in black & white and have to tune to one
> (or more) different channels and then go back to the original channel get
> colour. Occasionally a channel will later go black and white again and I
> must apply the same fix. Both boxes are the 'new' hardware version.
> > >
> > > Could this be a driver problem, hardware problem, or fine-tuning
> problem??
> > >
> > > I saw a post from 2006 that describes a similar issue but using NTSC:
> > >
> > > http://www.isely.net/pipermail/pvrusb2/2006-January/000384.html
> > >
> > > I'm running Ubuntu server 10.10 64-bit with the driver from
> linux-s2api-tbs6980-1_20101024 (commercial mod for the Tenow International
> dual satellite card) in which I made a small modification to set:
> > >
> > > .pixelformat    = V4L2_PIX_FMT_MPEG,
> > >
> > > ...in the pvrusb2-v4l2.c file in order for tvheadend to recognise it as
> a valid source.
> > >
> > > Since both boxes behave the same way, I suspect this is an issue with
> the driver. What can I do to debug the issue further?
> > >
> > >
> > > Thanks,
> > >
> > > Tom
> > > --
> > >
> >
> > I have tried "pre-tuning" several channels with a script using v4lctl
> > before launching tvheadend, but this does not solve the problem. I've
> > compared the settings while B&W vs colour but can't find any
> > differences. What could be causing this?
>
> Also, is this only happening with the RF tuner or can you also reproduce
> it with the composite and s-video inputs?  (If it's just the tuner, then
> the search space is narrowed down considerably.)
>
> Incorrect tuning might also do this - if the tuning isn't right then the
> hardware might not be finding the color information in the signal.  That
> can definitely happen with NTSC, but the last time I actually *saw* that
> effect was back in the 1970's using a TV with a crappy mechanical tuner.
> Modern digital tuners usually don't have a problem like this unless
> you're really sending it an incorrect frequency.
>
> There are methods possible by which one can get the tuner and cx25840
> kernel modules to report the in-use video standard.
>
> Has nobody else ever seen this problem?  (Realize that the case in 2006
> was definitely bad hardware so it doesn't count.)
>
>  -Mike
>

Hi Mike,

Thanks for your comprehensive and informative response. My hardware is fine,
and I am happy to report I have solved the problem. I hope this information
may help to solve it for others.

When I initially set up the WinTV boxes, I used the 'scan' utility to obtain
the channel frequencies. It turns out that most of the frequencies were
wrong, and I believe I know why this happened. My local cable provider is
using PAL B/G but it seems also places some programmes on other (D/K)
frequencies adjacent to the official B/G ranges. I think this must have
confused the utility and it chose the D/K channel spacing instead of B/G.

To solve the issue, I found some PAL B/G frequency charts via Google, erased
all of the errant values and created new ones following the chart. I then
went back and filled in the D/K frequencies (which are between the official
bands) and now the channels tune perfectly.

Thanks again for your help, and I hope you'll check out Tvheadend because it
really is an excellent back-end for both DVB and analogue feeds:
lonelycoder.com/hts .


Regards,

Tom
--