[GEM-dev] interlaced output from Gem?

cyrille henry cyrille.henry at la-kitchen.fr
Wed Mar 12 12:26:11 CET 2008



Claude Heiland-Allen a écrit :
> Hi all,
> 
> Does Gem (or OpenGL in general) have any support for interlaced output? 
>   The extra temporal resolution would be nice when rendering for display 
> on a TV, as the spatial resolution would suck anyway.
> 
I think rendering at 50fps on the TV out should do that.

if you want to make a DVD, the best is probably to have a 50fps movie. then, you should be able to downgrade the quality to 25i with a good DVD authoring software. 

cyrille

> 
> Here's an IRC log from #dataflow :
> 
> 09:56 < ClaudiusMaximus> anyone got any tips for generating interlaced 
> video in Gem? i think i need to set the gemwin to 2x the framerate and 
> 1/2x the vertical resolution, and do some small vertical translations 
> up/down depending on which field is the current one
> 09:56 < ClaudiusMaximus> it's the last step that i'm not sure exactly 
> how to do
> 09:57 < ClaudiusMaximus> rather i know how, but just not what values i 
> should put in..
> 10:29 < rdz> ClaudiusMaximus, i once thought about the same..
> 10:29 < rdz> ClaudiusMaximus, actually it would suffice to have only 
> half of the vertical resolution (the scan lines)
> 10:30 < ClaudiusMaximus> rdz: i'm not sure, because the different fields 
> are displayed at slightly different vertical positions..
> 10:30 < rdz> ClaudiusMaximus, yeah exactly..
> 10:30 < rdz> ClaudiusMaximus, this could be accomplished by shifting 
> half a line
> 10:32 < ClaudiusMaximus> rdz: what about OpenGL line widths being 
> measured in pixels?  wouldn't that cause problems like "fat horizontal 
> lines"?
> 10:35 < rdz> ClaudiusMaximus, sorry.. i didn't understandyour last line
> 10:35 < rdz> what do you mean by fat lines?
> 10:36 < ClaudiusMaximus> rdz: well, if you do "draw line, width 1" you 
> get a 1pixel line, right
> 10:36 < rdz> yeah
> 10:36 < rdz> understood
> 10:36 < ClaudiusMaximus> and 1pixel at half the vertical resolution is 
> 2x as fat as 1pixel at the full horizontal resolution
> 10:36 < rdz> hm...
> 10:36 < rdz> yo........
> 10:36 < rdz> seems like there should be native support for that in 
> gem/openGL
> 10:38 < ClaudiusMaximus> i'm currently leaning towards rendering 720x576 
> @ 50fps and using a field-aware downscaler
> 10:39 < ClaudiusMaximus> especially as i want to blur everything 
> slightly to avoid horrible compression artifacts
> 10:39  * ClaudiusMaximus been reading this page 
> http://www.adamwilt.com/Tidbits.html#CGs
> 10:40 < rdz> ClaudiusMaximus, are you producing for tv ? ;-)
> 10:40 < ClaudiusMaximus> rdz: well, i want to make any dvds i produce 
> look better than they do currently...
> 10:40 < rdz> ClaudiusMaximus, i see
> 10:40 < ClaudiusMaximus> rdz: so that's a sorta-yes ;)
> 10:40 < rdz> ClaudiusMaximus, have you already asked gem-dev about it?
> 10:41 < rdz> ClaudiusMaximus, interlaced 3d renderings....... sounds 
> very promising...
> 10:41 < rdz> i'd love to see a way to be able to do that
> 10:41 < ClaudiusMaximus> rdz: not yet, will post something today I think
> 
> 
> Thanks,
> 
> 
> Claude




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