VLC scaling on VGA

Rudolf Cornelissen rag.cornelissen at inter.nl.net
Mon Oct 15 19:11:24 CEST 2001

Hello once again,

About the 720x405 pixel size on VGA:
VLC uses the horizontal 720 pixels as the basis for calculations on the 
'aspect ratio locked' vertical number of pixels (always 405 then).

VLC could also do it the other way around: take the vertical resolution as 
the basis, so 480 for NTSC and 576 for PAL. For NTSC horizontal res. would be 
853 pixels, while for PAL this would be 1024 pixels then.

I suspect (don't know for sure) that the currently exhibited 'moirre' 
patterns will be gone then, because with the latter method you don't loose 
pixelinfo, but you 'add' info. For pal you would have to insert a 'vertical 
line' after each two 'vertical lines' of real data (or so). I suppose you 
could interpolate between the previous and next vertical line then.

I can imagine that CPU load will rise because more pixels have to be drawn, 
but on the other hand, I can imagine also that upscaling is easier than 
downscaling which in that case will drop CPU load again...
Also the output picture will be sharper than with the currently used method.

Anyway: Windows software players use the upscaling method.

Of course, all this is only for display on VGA, because most TVencoders 
support max. 800x600 (rescaled) resolution anyway. Besides: one will (should) 
mostly use the 'disable aspect ratio lock' then also. 

If the 'aspect ratio lock' is disabled, VLC should make the default windows 
720x480 and 720x576 resp., and skip the scaling as mentioned earlier 
(previous mail).

BTW: 4:3 movies should be in the same windows if aspect ratio lock is 
disabled (no rescaling either), and should be a bit rescaled (same sort of 
method as 16:9) for display on VGA.

Well, thanks for listening again. I will leave you all 'to it', and follow 
development of the VLC with great interest...

Best regards,

Rudolf Cornelissen.

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