[mythtv-users] Nvidia 260 yuv gives better image quality

[Andre]

On 12 Nov 2010, at 09:21, Paul Gardiner wrote:

> On 10/11/2010 11:57, Jean-Yves Avenard wrote:
>> Hi
>> 
>> On 9 November 2010 02:35, Andre<mythtv-list at dinkum.org.uk>  wrote:
>>> I recently upgraded my frontend to mythbuntu 10.10 to get GT220 HDMi audio working (upgraded alsa on 10.04 was giving grief) and as a consequence got Nvidia 260.19.06.
>>> 
>>> Big improvement for me, Nvidia settings now has an RGB/YUV setting and this is resolved a nagging problem I had with vdpau. Previously in shadows and dark scenes there is a colour cast which varies from recording to recording in it's colour and severity, the display (a DLP projector) is calibrated to reduce this but it varies so still shows up some of the time. Set display mode to YUV and immediately shadows are as they should be, detail in shadows is clear and the correct colour :-))
>> 
>> Did you ever try the VDPAU colorspace and studio levels filter?
>> 
>> You would have achieved the same results with earlier nvidia drivers.
> 
> Interesting. Are you saying the filters can be used to give YUV output?
> Or have I misunderstood what Andre is saying?

No YUV but the studio levels filter will give limited range RGB, (which was the other innovation in 260) but only for vdpau video rendering not for the desktop or theme, 260 gives you that everywhere. This is especially important to anyone who's TV doesn't work with full range RGB, I especially noticed this when trying to use Myth for photo slideshows, so I didn't use that feature, maybe I can now. The conversion from limited range (which the video will always be) to full range may also introduce some small errors, severity depending on how far back vdpau applies this conversion.

I suspect that studio levels still outputs the same thing for video regardless of the nvidia setting, well I hope it does! This setting should be irrelevant when outputting YUV but I'm starting to think that I need to check all these combinations!!

The auto colour space filter is essential too as SD video and HD video use different colour spaces, having the wrong one will introduce further errors. You get washed out SD if the HD colour space is incorrectly used and potentially crushed colours or at least exaggerated and with some incorrect colours. This is a gross simplification of what actually happens, suffice to say it's important to use the correct one.

This effect can sometimes be seen when a broadcaster is upscaling for a HD channel and doesn't set the upconverter properly, sadly this happens quite often. I'm told material from rights holders sometimes arrives already upconverted badly, of course "fixing" that introduces new and "interesting" colouration.

Andre


> Cheers,
> 	Paul.
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>