[mythtv-users] OT: LED or Plasma (was Advice on choosing a TV)

Paul Gardiner lists at glidos.net
Fri May 28 09:17:56 UTC 2010

Andre wrote:
> On 28 May 2010, at 00:00, Paul Gardiner wrote:
>> Andre wrote:
>>> Alternatively and much more simply are you using studio levels (vdpaustudio) out from MythTV? If not there is a scaling of the display output 16-235 scaled to 0-255, this introduces some small artefacts that a plasma display will accentuate.
>> Now I have MythTv driving the TV, I'm getting results much darker than
>> any other source - all the others being much the same. I.e., dark areas
>> are darker. First thought when I saw this was that it might be
>> the 16-235 to 0-255 scaling, so I put vdpaustudio in the filter box.
>> It made no visible difference. Any other ideas? It would be really nice
>> if all my sources were the same, so I can just calibrate once.
> You should be able to see the difference vdpaustudio makes, I think we established that you have a critical eye ;-)

Cross posts. Turns out silly Paul didn't realise that 0.23 was out.

> Have a look for the full/video setting in the TV, the counterpart to vdpau studio also superwhite, worth checking RGB/YCrCb settings as you have already seen the green & magenta look that feeding RGB into YCrCb gives. Also you can have different settings per input so I'd swap the inputs around and determine if MythTV is really darker or just connected to a differently setup input. Bizarrely the only mode I could find all the settings exposed in with that TV was Game mode, which gave me the best results driven from a computer when correctly adjusted.

Don't see anything like that in the settings, but hopefully when I
upgrade I wont need to.

I never got to the bottom of my green magenta problem. I see what you
mean about it being Y mapped to u and or v. It looks like the nvidia
driver can't do interlaced modes properly. I did see something odd in

GetModeLine - scrn: 0 clock: 13500
GetModeLine - hdsp: 720 hbeg: 732 hend: 795 httl: 864
               vdsp: 576 vbeg: 580 vend: 586 vttl: 624 flags: 26

Shouldn't vttl be 625?  If I set up a mode by hand with 625 in
place of 624 then the TV OSD doesn't say "576i".

> Really you need to calibrate from inside MythTV as well as DVD/Bluray, I'd start with Bluray to get a feel for it then go to Myth with a rip of the setup DVD or BBC HD Testcard, there are some free patterns you can download from AVForums too.
> Would be really really nice if VDPAU could be configured to output YCrCb instead of RGB but I don't know if it's capable or even if HDMI can use that colour space in computer display mode.

I've always thought that. We convert YCrCb to RGB in the frontend, and
then the TV converts it back to do its colour processing. Worse when
using S-Video or Component: we convert to RGB and then back again in
the front end.


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