[GEM-dev] interlaced output from Gem?

[Claude Heiland-Allen]

cyrille henry wrote:
> 
> 
> 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.

Any suggestions for such downgrading software?  I'm running Linux on a 
no-budget; links to algorithms would be ok too, so I could implement 
them myself if no Free tool exists already.

> cyrille

Thanks,


Claude


> 
>>
>> 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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