[GEM-dev] interlaced output from Gem?

Claude Heiland-Allen claudiusmaximus at goto10.org
Wed Mar 12 12:00:11 CET 2008


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.


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
-- 
http://claudiusmaximus.goto10.org




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