384×240 scaled to 1920×1440 instead of 2304×1440

[LaminGaming]

After looking through the resolutions that the OSSC can output for 384×240 optimised, I noticed that 6x is scaled to 2304×1440 (6x on both horizontal and vertical), even though 1920×1440 would’ve been possible (5x on horizontal and 6x on vertical). I don’t know if this is just an oversight, or if there’s a technical reason, but would it be possible to change this in a firmware update? As I feel this is a missed opportunity to get an integer scaled 4:3 aspect ratio without having to squash/stretch the image.

384×240 scaled to 2304×1440

384×240 scaled to 1920×1440

[Zacabeb]

It might be caused by the limitations to speed and available lanes in the FPGA, where at higher resolutions the final scaling step is done through 2x sample repetition onboard the HDMI transmitter.

If so, the OSSC Pro can’t scale to 1920×1440 because the 5x scaling factor isn’t divisible by 2, but scales well to 2304×1440 because there, the 6x scaling factor is divisible by 2.

[LaminGaming]

Interesting, I guess that makes sense. I had a feeling it might potentially be a limitation of the OSSC but wasn’t sure.

If it was possible, I think it would’ve been ideal if you had control over the horizontal multiplication in some way, maybe as a separate setting or something. At least then, it would help to account for particular resolutions with PAL and NTSC.

Speaking of PAL, I recently found out that I can 4x scale 480×270 (512×288 cropped) to 1440×1080 (3x horizontal and 4x vertical) by using the 384 optimised mode, which gives me an integer scaled 4:3 aspect ratio. Whereas, the 512 optimised mode can only 4x scale 480×270 to 960×1080 (2x horizontal and 4x vertical), which doesn’t work. This is why I think having control over the horizontal multiplication would help in instances like this.

Here’s a screenshot I took showing a 512×288 game at 4x using the 384 optimised mode:

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