[mythtv-users] Really washed out picture since upgrade to 0.24.0

[Andre]

On 21 Nov 2010, at 05:35, Kevin Johnson wrote:

> I have had some issues with this also.  Since the new nvidia drivers, I noticed some things work opposite of what I think they should.
> My panny plasma will not do full range.  So with .23 I used the vdpaustudio with good results.
> Now with .24 I have tried several different options to try and get the blacks correct.
> I tried removing the vdpaustudio option in mythtv and using rgb limited in nvidia-settings.  This resulted in the blacks still being slightly crushed.
> Then I tried setting the nvidia driver to full range and using vdpau studio in mythtv.  That made everything look grey.



> Ultimately, I get the correct blacks by setting nvidia to rgb limited, and using vdpaustudio in myth.

In theory this is the correct setting for a display that cannot do full range rgb so maybe we have all got used to how it looked before when it was wrong! 

This whole incompatible/wrong levels thing has annoyed me in the past and it was only when vdpaustudio was added that I started using mythfrontend for watching TV.

I have been using the yuv desktop setting (see other thread) since discovering it because this gives better image fidelity with my display. I haven't tried removing vdpaustudio but I wouldn't expect to see any difference as studio or limited levels has no meaning in yuv mode, ok it _shouldn't_ have any meaning, maybe I'll run through some settings this evening and see what's going on.

It may be useful to try some test patterns, there are some free ones here:

http://www.avsforum.com/avs-vb/showthread.php?t=948496

The black, apl & white clipping patterns, 1,2 & 3 should show up exactly what the nvidia driver and vdpau settings are doing and what your display can handle.

I keep a BBC HD testcard clip knocking around too but I don't think they broadcast it anymore and that's no good for anyone outside the UK. I'd post a mytharchive of it it on my server but I suspect the BBC would not be happy about that :-(

Also if a suitably knowledgable developer is passing by it would be good to know how the internal player handles these issues, eg is vdpaustudio a flag passed to the vdpau api or does it trigger different myth code? Is vdpau just a "magic black box" into which video is passed and pictures appear on the display or is there significant myth player code interacting with the API, if so how does the whole yuv/rgb/limited or full issue get handled?

I'm trusting that a mythvideo playback of test patterns is treated the same as a digital (DVB/ATSC) broadcast recording, assuming internal player is used.

I also understand there is a flag in the video stream related to full/limited with regard to the source but I have seen broadcast examples where this was wrong and set top boxes seem to ignore it anyway. Really not sure why this exists, surely after going through the mpeg2/4 mill full or limited is purely a local playback issue?

At the risk of significant developer ire I'd suggest maybe a "setting" to render the theme and software rendered video as full or limited range would be beneficial ;-) Just for those few not using vdpau and nvidia 260 drivers, both of you.... :-)



> Nothing seems to work exactly like you would think it would.
> Not sure what the deal is???? 

I'll see if I can work it out this evening, having a projector means there is no point in trying any calibration related stuff during daylight hours, bulb fade means it's about time I re-calibrated anyway.

Andre
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