Tearing problem at bigger overlay sizes

[Matthias Hopf]

On Jan 12, 09 22:17:28 +0100, Christiaan van Dijk wrote:
> > If you're using guardband clipping, this means that you're really
> > rasterizing (and throwing away) an awful lot of pixels. And this is
> > still fast enough? Fascinating.
> Yep, not sure how the engine is handling the non-used parts of the 
> triangle, if I display the entire triangle the tails seem to be filled 

They are rasterized, but probably dumped before fragment shader
invocation.

> To see if I could get a tear free displayed I tried rendering the source 
> block (SD TV 16:9) to the destination block (HDTV 1080p/50Hz) in quads 
> of 100 lines max. The idea was to wait for a V-sync and refresh the 

That was my initial idea how to deal with that.

> tear free. Sometimes the diagonal tear can be seen in one or more (2..4  
> segments out of 11) of the 100 line segments. This last point is really 
> puzzling, this could indicate the graphics engine is just keeping up 
> with the refresh, slightly slower or slightly faster.

Could be a caching issue, pushing out the cache after each block might
help.

Matthias

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