[mythtv-users] Re: Mythtv, nvidia and DVI mystery

[Neil]

Hi Brad, 

I did more testing and looks like it's not a mythtv issue. Hmmm. I talked to 
the nvidia guys and they told me that I should make sure that Vsync and 
vblank are checked in nvidia settings and that I have to restart mythtv. I 
even did recompile myth so that it has opengl support. Btw, since I was 
testing more, I saw that tearing I was mentioning when I was playing Unreal 
Tournament 2004. I recreated the tearing coz my camera is failing to capture 
it. Have a look of what I really meant by tearing. 
http://restricted.dyndns.org/ut2004-tearing.jpg
So I guess, you are right. It might be an interlace bug. So could this be an 
nvidia issue? 

Now, I have another question. Before, I was using US digital hdtv receiver. 
My hdtv knows if it's 480i, 480p or 1080i. But now, using my linux HTPC, 
it's all the way 1080i since I've configured X that way. I think, that's the 
reason why I have the kind of tearing. Is there a way for us to 
automatically tell our HDTV that it's a 480p or 1080i program even if our 
Xorg is set at 1080i? 

Thanks. Any comments from anyone are greatly appreciated. 



Neil writes: 

> Brad Templeton writes:  
> 
>> On Fri, Mar 04, 2005 at 03:54:56PM -0600, Neil wrote:
>>> Brad Templeton writes:   
>>> 
>>> 
>>> It's totally different from interlace artifacts. Here is an example of 
>>> how I am understanding on what you meant by interlaced artifacts - 
>>> http://neuron2.net/LVG/inthead.jpg Please correct me if I am wrong.
>> 
>> Yes, those are interlace artifacts.  These only occur on moving objects,
>> however, not on stationary ones.   Smart deinterlacers know the 
>> difference
>> between moving objects and stationary ones, and deinterlace differently.  
>> 
>> If your TV is native 720p, like many Mitsubishis, the main reason to run
>> 1080i video at 1080i is that the TV probaly has a high quality hardware
>> deinterlacer in it you would then take advantage of.  It is carefully
>> tuned to reduce 1080i to your native resolution.  
>> 
>> If your software will do it better than the TV, better to run at 720p and
>> have myth do it.  But all myth offers are things like linear blend (which
>> blurs moving objects a lot) and bob (which works well with some artifacts
>> and some shimmer on certain things.)  
>> 
>>> If so, then, it's different. I only see mine in just 1 line but random Y 
>>> coordinates. It only happens on very fast moving objects. Here is an 
>>> example. Like in the program American Idol, I don't know if you have 
>>> that program. During a presentation of a performer, behind her is a 
>>> large flat
>> 
>> Unfortunately, we do have it, but I don't record it.  
>> 
>> But American Idol is on Fox, and Fox transmits at  720p, not 1080i.  
>> 
>> You definitely should not be taking a 720p signal and running it to your
>> TV at 1080i, especially if your TV is not native 1080 lines.   If you
>> have a native 720 line TV like my Mitsubishi, avoid this like the plague.
>> Use RANDR.  
>> 
>> 
>>> Overscan? I guess, overscan only has something to do with picture being 
>>> larger than my hdtv. Fortunately, mythfrontend comes with X&Y offsets, 
>>> size that we can tweak. And with that, I am able to size my watching to 
>>> almost 99% of my hdtv screen.
>> The problem I see with overscan is that I don't know what happens when
>> you send a 1080i signal in that is not being downscaled at the ratio
>> the TV is tuned for on other 1080i signals it gets, like from the tuner.
>  
> 
> My mitsubishi 48313, based from the manual, only supports 480i, 480p and 
> 1080i, no 720p. Here is another one, I'm also recording other programs 
> which is only at 480. I do see those tearing too in fast moving objects. 
> And btw, about twinview, it is true that it degrades performance since it 
> doesn't use overlay on multiple screens, just the first one. It uses 
> blitted but I don't know what it is. It might be software rendering.  
> 
> here it is, http://www.restricted.dyndns.org/README.txt  
> 
> You can find it in:
> FREQUENTLY ASKED TWINVIEW QUESTIONS:  
> 
> Here is an excerpt:  
> 
> Q: Do video overlays work across both display devices?  
> 
> A: Hardware video overlays only work on the first display device.
>  The current solution is that blitted video is used instead on TwinView.  
> 
>  
> 
> Well, the guys at nvidia channel told me that it might be a real nvidia 
> driver issue. I just have to wait then....  
> 
> But, I'm doing more investigations. I'm gonna try EDID enabled again and 
> see if I can get it to work at 1080i.  
> 
> I'll let you know...Btw, your info is very helpful.  
> 
> Thanks,  
> 
> Neil
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users