Mailing List Archive: MythTV: Users

VDPAU picture degradation, possibly since 0.24 to 0.25 switch

Index | Next | Previous | View Threaded

lists at glidos

Aug 19, 2012, 12:40 PM

Post #1 of 5 (316 views)
Permalink

VDPAU picture degradation, possibly since 0.24 to 0.25 switch

For some time now I've felt I was getting worse picture
quality than I used to. It's very subtle so I wasn't sure
if I was imagining it or not, but now I have definite
evidence that my myth frontend is the cause. It seems
to be producing too high a contrast even though all
picture settings are at 50%. It isn't because of confusion
over studio and PC settings. My TV can be set to expect
either, and I see the same problem with TV and Myth set
to studio or with TV and Myth set to PC.

Tonight while watching the news I noticed a strongly
lit skin area that looked wrong in colour. The pink
went to yellow and then to white as the intensity
increased. If you think about it, that's exactly
what you'd expect if the RGB values were being
clipped: for pink, R is strongest then G then B.
First R would become clipped, making the colour
yellow, and then both R and G, making the colour
white.

When I'd noticed that sort of discolouration before,
I'd put it down to the source, but I realised tonight,
that if it was the source, it should be impossible to
adjust it out. That's where I got the evidence that
the problem with the frontend: I found that I could
adjust it out, but only by adjusting Myth's settings,
not by adjusting my TV; it seems the RGB values are
being clipped before getting to my TV, hence it must
be Myth that's doing the clipping.

Has anything changed in the YUV => RGB conversion
for vdpau recently? Or has anybody noticed a problem
with recent nvidia drivers?

Cheers,
Paul.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://www.mythtv.org/mailman/listinfo/mythtv-users

peper03 at yahoo

Aug 19, 2012, 1:09 PM

Post #2 of 5 (298 views)
Permalink

Re: VDPAU picture degradation, possibly since 0.24 to 0.25 switch [In reply to]

On 19/08/12 21:40, Paul Gardiner wrote:
> For some time now I've felt I was getting worse picture
> quality than I used to. It's very subtle so I wasn't sure
> if I was imagining it or not, but now I have definite
> evidence that my myth frontend is the cause. It seems
> to be producing too high a contrast even though all
> picture settings are at 50%. It isn't because of confusion
> over studio and PC settings. My TV can be set to expect
> either, and I see the same problem with TV and Myth set
> to studio or with TV and Myth set to PC.

I've not noticed any problems like this using VDPAU but is it possible
the TV has more than one setting? I've had something similar once or
twice and it was always due to the TV trying to be clever with
auto-contrast, auto-gamma, auto-whatever. I even had the same problem
today because the gamma setting had been accidentally set to 'Energy
saving'. The brightness of the picture kept changing depending on which
menu entry I had selected in Myth (presumably due to the background
image changing).

These settings are often assigned per input as well, so if, for example,
everything looks great on from a Blu-Ray player connected to HDMI1 but
terrible on Myth connected to HDMI2, it may not be Myth at fault. You
would need to check that the TV settings for HDMI2 were also correct.

This may well not be the cause of your problem but it sounded too
similar to effects I've had in the past with TV settings to leave it
unmentioned.

Richard.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://www.mythtv.org/mailman/listinfo/mythtv-users

freedenizen at gmail

Aug 19, 2012, 1:33 PM

Post #3 of 5 (300 views)
Permalink

Re: VDPAU picture degradation, possibly since 0.24 to 0.25 switch [In reply to]

On Sun, Aug 19, 2012 at 12:40 PM, Paul Gardiner <lists [at] glidos> wrote:
> When I'd noticed that sort of discolouration before,
> I'd put it down to the source, but I realised tonight,
> that if it was the source, it should be impossible to
> adjust it out. That's where I got the evidence that
> the problem with the frontend: I found that I could
> adjust it out, but only by adjusting Myth's settings,
> not by adjusting my TV; it seems the RGB values are
> being clipped before getting to my TV, hence it must
> be Myth that's doing the clipping.

even if it is the source you may have been able to adjust it such that
it appeared more normal. Try playing it back with vlc, or if you have
recording from 0.24 see if those exhibit the problem.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://www.mythtv.org/mailman/listinfo/mythtv-users

mtdean at thirdcontact

Aug 19, 2012, 2:22 PM

Post #4 of 5 (295 views)
Permalink

Re: VDPAU picture degradation, possibly since 0.24 to 0.25 switch [In reply to]

On 08/19/2012 03:40 PM, Paul Gardiner wrote:
> For some time now I've felt I was getting worse picture
> quality than I used to. It's very subtle so I wasn't sure
> if I was imagining it or not, but now I have definite
> evidence that my myth frontend is the cause. It seems
> to be producing too high a contrast even though all
> picture settings are at 50%. It isn't because of confusion
> over studio and PC settings. My TV can be set to expect
> either, and I see the same problem with TV and Myth set
> to studio or with TV and Myth set to PC.
>
> Tonight while watching the news I noticed a strongly
> lit skin area that looked wrong in colour. The pink
> went to yellow and then to white as the intensity
> increased. If you think about it, that's exactly
> what you'd expect if the RGB values were being
> clipped: for pink, R is strongest then G then B.
> First R would become clipped, making the colour
> yellow, and then both R and G, making the colour
> white.
>
> When I'd noticed that sort of discolouration before,
> I'd put it down to the source, but I realised tonight,
> that if it was the source, it should be impossible to
> adjust it out. That's where I got the evidence that
> the problem with the frontend: I found that I could
> adjust it out, but only by adjusting Myth's settings,
> not by adjusting my TV; it seems the RGB values are
> being clipped before getting to my TV, hence it must
> be Myth that's doing the clipping.
>
> Has anything changed in the YUV => RGB conversion
> for vdpau recently? Or has anybody noticed a problem
> with recent nvidia drivers?

/me guesses studio colors aren't properly configured on your system

Mike
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://www.mythtv.org/mailman/listinfo/mythtv-users

lists at glidos

Aug 19, 2012, 4:09 PM

Post #5 of 5 (296 views)
Permalink

Re: VDPAU picture degradation, possibly since 0.24 to 0.25 switch [In reply to]

On 19/08/2012 21:33, Free Denizen wrote:
> On Sun, Aug 19, 2012 at 12:40 PM, Paul Gardiner <lists [at] glidos> wrote:
>> When I'd noticed that sort of discolouration before,
>> I'd put it down to the source, but I realised tonight,
>> that if it was the source, it should be impossible to
>> adjust it out. That's where I got the evidence that
>> the problem with the frontend: I found that I could
>> adjust it out, but only by adjusting Myth's settings,
>> not by adjusting my TV; it seems the RGB values are
>> being clipped before getting to my TV, hence it must
>> be Myth that's doing the clipping.
>
> even if it is the source you may have been able to adjust it such that
> it appeared more normal. Try playing it back with vlc, or if you have
> recording from 0.24 see if those exhibit the problem.

Yes, you are right. I just realised the flaw in my logic. If
the source has out of range Y then Myth can correct it
before the RGB conversion, but once the conversion is
done it is too late, so the TV can't correct it.

Also I just did some tests with samples from the AVCHD
Blu-ray and my set up is pretty much perfect. I guess
I was imagining the degradation.

Thanks for the replies - you, Richard and Michael.

Cheers,
Paul.
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://www.mythtv.org/mailman/listinfo/mythtv-users

Index | Next | Previous | View Threaded

Interested in having your list archived? Contact Gossamer Threads