Can GC/Wii content be forced to output 240p ?

[DrHouse64]

Afaik, no homebrew can do this right now.
I know Swiss can force GameCube games to play at 240p, but you need the retail disk and no SD/USB loader implements this feature yet.
The thing is, interlacing was a clever trick to double output resolution, but nowadays causes more harsh than good.

Can it theoretically be possible ? 

[Kurausukun]

Theoretically, yes, but I don't know if it would be as trivial as adding the option into Dolphin alongside the other IR options or whether we make assumptions in code based on the fact that the resolution is always supposed to be >= 480i. A dev would have to answer that.

[SomaCruz]

(09-28-2018, 02:22 PM)Kurausukun Wrote: Theoretically, yes, but I don't know if it would be as trivial as adding the option into Dolphin alongside the other IR options or whether we make assumptions in code based on the fact that the resolution is always supposed to be >= 480i. A dev would have to answer that.

That actually would be really cool. And the option NOT to skip on idle( i know u can do it in dolphin ini, but still ), but i guess i can't do anything about it  

[MayImilae]

To the GameCube and Wii, 240p isn't really anything special, since they just run in double-strike. On typical analog crt televisions, there is no 480p or even 240p, they run exclusively in 480i, period. So to get a 240p image in such an environment all pre-GameCube consoles double up on the vertical axis, sacrificing resolution for progressive output. Before Dolphin supported double-strike properly, you could literally see this in virtual console games. (unless you set the emulated wii to progressive mode, then it wouldn't try to use double-strike at all)



In a progressive output that image looks stretched vertically, but to an interlaced signal that image above has 240 progressive lines. Then the XFB can cut out the black bits to the right of the rendered frame and tada, 240p! This does require XFB shenanigans since the GameCube and Wii rendrDouble-strike is a very simple technique and classic technique, so there is nothing special or weird here - this is basically identical to how the NES, SNES, and N64 work internally, just now performed by XFB. Also that's why the GameCube and Wii do not have a 240p output mode per se, since it's still 480i. Almost all virtual console games run in double-strike, since that's the best way to render classic games on analog tvs. Of course if using component, the Wii is set to 480p output, and XFB knows not to use double strike and scales on both axis evenly.

Dolphin of course only emulates some facets of the Wii's output, but thanks to emulated XFB improvements Dolphin no longer needs to tell the emulated wii that it is or isn't progressive output - Dolphin's emulated XFB can adjust things as needed without the user messing with it at all!

Anyway, here are a few times where we have talked about it on the blog!

https://dolphin-emu.org/blog/2016/02/02/dolphin-progress-report-january-2016/#40-8640-better-video-mode-detection-by-phire
https://dolphin-emu.org/blog/2017/11/19/hybridxfb/#panning
https://pt.dolphin-emu.org/blog/2015/10/01/dolphin-progress-report-september-2015/#40-7517-derive-field-timings-from-video-interface-registers-by-booto

Of course it is possible to output 240p output via component, as swiss shows, but why would you when double strike is available? Also I don't know what level of hackery swiss is committing to make it do that. I imagine quite a lot, since the consoles aren't designed for that at all!

DrHouse64 Wrote:The thing is, interlacing was a clever trick to double output resolution, but nowadays causes more harsh than good.

Yea um, no. Interlacing was a bandwidth hack - basically compression, in an analog fashion. Analog CRTs were technically capable of 480p easily, as they have 480 lines of phospors, they just needed different timings. As evidenced by broadcast video monitors, crt computer monitors, component crt tvs of the 2000s, and mod forums adding circuitry to old televisions, etc etc. But typical analog televisions weren't able to switch modes since they were... well, really, REALLY dumb. They just operated on pre-set timings literally hard-wired into the devices.

[DrHouse64]

Thanks for the explanation.
So, hm, yes, I want 240p double-strike. As you said, CRTs don't run at a pure 240p resolution anyway, that's why we never mention double-strike in retrogaming because it's obvious.

Here's the context : I have an OSSC, it's a line multiplier.
For 240p content, it's good for 1080p monitors because it can scale it to 5x, filling the screen vertically, with some lines cropped at top and bottom, most of them are overscan anyway so it's fine.
For 480p content, it's problematic because integer scaling doesn't really fit 1080p. With 2x, it outputs 960p, thus vertical black borders appears on a 1080p screen.

That's why I was curious about forcing 480p content to output a 240p image.
I can of course use my monitor scaling feature to make the 940p input to fill the screen, but non-integer scaling always means visual artefacts, and I love to try useless experimentations