[mythtv-users] OT: Optimising 50Hz over 60Hz VGA (was: Smoother video playback?)

Stroller linux.luser at myrealbox.com
Tue Apr 10 23:49:02 UTC 2007

On 10 Apr 2007, at 17:45, Ben Lancaster wrote:
> On 10 Apr 2007, at 15:45, Mark Kendall wrote:
>> On 4/10/07, Ben Lancaster <lists at benlancaster.co.uk> wrote:
>>> I thought this was the case some time ago. Unfortunately I've been
>>> unable to find a 1280x720 or 1360x768 50Hz modeline that works with
>>> my Samsung HDTV over VGA. I don't suppose you have one? ;-)
>> Unfortunately no - they only support 60Hz over VGA. Does your video
>> card have dvi out?
> In light of the above, are there any ways of improving PAL over 60Hz
> VGA?

Probably not. It's all to do with the number of frames-per-second the  
material was originally recorded at - I read an article about this a  
while ago and there are probably lots of other articles on the net if  
you search.

As I understand it playing PAL means that 50 frames are played each  
second - in order to play that PAL material back at 60hz it means  
that you play back those same frames but also insert a few more each  
second to make up the difference. It's this one frame in 5 which is  
identical to the previous one that causes the "stutter" that I guess  
you're seeing.

I guess that hypothetically one's playback software could make a  
composite image by averaging the pixel values of two frames and  
insert the composite between the two in order to reduce the stutter,  
but I don't believe this happens in practice.

> The only solution I can see is to get a video card with component TV
> Out; I'm not sure this annoyance merits the 40 expenditure.

I think you might notice the quality improvement from this. I guess  
it depends on how much your time / entertainment is worth - how long  
have you spent discussing this already, and how long could you easily  
spend tinkering with modelines in your xorg.conf? I'll bet one could  
easily spend 10 hours arsing around, in which case you'd only be  
saving yourself 4 / hour even if you DID get it all working.

There are lots of places you can buy these cards which have an  
accommodating returns policy - under the Distance Selling Act you can  
now return a product for any reason. I happen to know that PC World  
sell PNY cards with a component-out dongle, so it doesn't need to  
cost you anything to try.


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