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Question concerning the "Overscan" page:
http://forums.nesdev.com/viewtopic.php?f=2&t=16178
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Author:  Firebrandx [ Wed Jul 05, 2017 11:00 am ]
Post subject:  Question concerning the "Overscan" page:

My question concerns the following line of the section called "For Emulator Developers":

But as a slight optimization, you can scale first (256 * 8/7 = 292) and then pad: stretch the 256x240 pixels to 292x240, 584x480, 876x720, or 1168x960 square pixels or 320x240 or 640x480 non-square pixels.

Isn't it better math to use scaling before correction? For example, say you want to scale to 4x. My formula for that is (256 * 4) * (8/7), which gives 1170 pixels, not 1168. It adds in that extra bit of accuracy in my opinion to scale before correction, not correct before scaling.

Author:  tepples [ Wed Jul 05, 2017 11:27 am ]
Post subject:  Re: Question concerning the "Overscan" page:

I think I chose the multiples of 292 because 292 is a multiple of 4, making 1168 a multiple of 16.
The difference between the two is 1.1406:1 (292/256) as opposed to 1.1429:1 (true PAR).

Author:  Firebrandx [ Wed Jul 05, 2017 4:56 pm ]
Post subject:  Re: Question concerning the "Overscan" page:

tepples wrote:
I think I chose the multiples of 292 because 292 is a multiple of 4, making 1168 a multiple of 16.
The difference between the two is 1.1406:1 (292/256) as opposed to 1.1429:1 (true PAR).


I see, so in the case of digital scaling, 1168 makes each pixel integer scaled, though a hair less accurate than scaling before correcting.

On the Framemeister, the horizontal axis is averaged on pixel edges, so 1170 looks just as smooth as any other width.

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