Prism component vs OEM component cables for Gamecube

The place for all discussion on gaming hardware
tesla246
Posts: 15
Joined: Sun Jan 12, 2020 8:50 pm

Re: Prism component vs OEM component cables for Gamecube

Post by tesla246 »

Unseen wrote:
NewSchoolBoxer wrote:
Since Extrems mentions (I think) some games with 4:4:4 encoding, is YCbCr locked to 4:2:2?
The Gamecube cannot output a real 4:4:4 signal, the video bus signal is always 4:2:2. extrems talk about 4:4:4 video from a Gamecube is deliberate misdirection, the actual signal is still 4:2:2 but each pair of pixels has the same color. With a non-standard conversion to analog this can look the same as an analog 4:4:4 signal with halved horizontal resolution, but in the digital domain it clearly not a 4:4:4 signal.
I remember reading (which I guess would be extrems) somewhere that flipper can sent RGBA copies to a different target (the Hi speed port) and thus circumventing the EFB 2MB limitation.
4:4:4 would be possible among other things, but an external device would be needed and it would eat up GPU resources copying the data, so I wouldn't know how viable it would be.

Would this not be possible or are you referring to just the 2mb EFB limitation which generally resulted in 4:2:2 RGB 556, that cannot be resolved?

Kind of funny how, in that generation of consoles the weakest one, the Dreamcast, has the superiour image quality; beautiful sharp, clean RGB 4:4:4 via HDMI, followed by PS2, GS can also output clean 4:4:4, but resolutions of games are all over the place, and lastly Xbox/GC tied for worst (though Xbox edges it out because of 720p)
User avatar
Extrems
Posts: 538
Joined: Sat Jan 30, 2016 5:01 pm
Contact:

Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

The eFB isn't the limitation, the XFB in main memory and the video interface is.

The eFB is converted to YCbCr 4:2:2 and copied to main memory so that the video interface can make use of it.

Only the DSP can access the Hi Speed Port, as it is an extension of ARAM, and so you need to copy to MRAM first then copy to ARAM.
User avatar
Rulumi
Posts: 114
Joined: Thu Jul 15, 2021 12:40 am

Re: Prism component vs OEM component cables for Gamecube

Post by Rulumi »

Would being able to bypass the actual VI would help in any way?
Like a custom VI emulation implementation on the Wii U different to Nintendo's one? Or will the XFB process be still a limitation in that scenario?
User avatar
Extrems
Posts: 538
Joined: Sat Jan 30, 2016 5:01 pm
Contact:

Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

That's the entire basis of the Hi Speed Port idea. We can copy to a texture format like RGBA8 instead.
tesla246
Posts: 15
Joined: Sun Jan 12, 2020 8:50 pm

Re: Prism component vs OEM component cables for Gamecube

Post by tesla246 »

Ah, I was re-reading a little bit about this in the ''cloning the gamecube component thread'' and you mentioned 720p and variable refresh rate would be possible with such a device, so I assumed (wrongly at that) the EFB would be circumvented.

Now, if I understand correctly, your solution is to build a new video interface via the Hi speed port. This can only work via ARAM bacause the Hi-speed port is an extension of that, which the GPU cannot access directly. So it has to go from EFB>MRAM>ARAM where the DSP copy's to the external device.

In this way 720p could be possible via tiling? Is that what you meant?

Also, how viable would 4:4:4 be in terms of performance? Does the GPU have enough overhead to copy multiple times?

And what other enhancements could be introduced? 24 bit colour is limited by the EFB, correct?
User avatar
fidde_se
Posts: 5
Joined: Mon Mar 21, 2022 10:13 am
Location: SWEDEN

Re: Prism component vs OEM component cables for Gamecube

Post by fidde_se »

Yes GIF's aren't the best but good enough too see here, so zooming in on Extrems picture to more clearly see what he means.

GCVideo-DVI v3.1 + Portta HDMI to YPbPr Converter + Generic Component Cable vs Retro-Bit Retro Prism Component Cable
Image

GCVideo-DVI v3.1 + Portta HDMI to YPbPr Converter + Generic Component Cable vs Nintendo GameCube Component Video Cable
Image
fernan1234
Posts: 2167
Joined: Mon Aug 14, 2017 8:34 pm

Re: Prism component vs OEM component cables for Gamecube

Post by fernan1234 »

fidde_se wrote:Yes GIF's aren't the best but good enough too see here, so zooming in on Extrems picture to more clearly see what he means.

GCVideo-DVI v3.1 + Portta HDMI to YPbPr Converter + Generic Component Cable vs Retro-Bit Retro Prism Component Cable
Image

GCVideo-DVI v3.1 + Portta HDMI to YPbPr Converter + Generic Component Cable vs Nintendo GameCube Component Video Cable
Image
Interesting. Doesn't it look there like the original GC cable has more pixel gradient (for lack of knowing the correct term) than everything else?
User avatar
Extrems
Posts: 538
Joined: Sat Jan 30, 2016 5:01 pm
Contact:

Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

This has already been explained.
Extrems wrote:The Nintendo GameCube Component Video Cable is set up with a 480p low-pass filter (240p/480i is approximated with linear interpolation) while the Portta HDMI to YPbPr Converter is set up with a 720p/1080i low-pass filter.

This difference only matter when you're oversampling the signal, and doesn't matter when using optimal sampling, although auto-phase detection will have an easier time with the latter.
The default settings on the RetroTINK-5X Pro oversample the signal such that each output pixel is a distinct sample on a given line.

If you look at a 480p checkerboard pattern using the Nintendo GameCube Component Video Cable on an oscilloscope, it looks like a perfect sine wave.
RebeL9
Posts: 164
Joined: Mon Jan 02, 2012 9:38 am

Re: Prism component vs OEM component cables for Gamecube

Post by RebeL9 »

Extrems wrote:
McNutts wrote:While I don’t have an in depth technical knowledge of these cables as some people have on this board I do own the HDMI adapter from Retro Bit and the prism cables on the way since I bought a Retro Tink 5x a few days ago.
Just get a Portta HDMI to YPbPr converter. You'll still have the sync drop issues from GCVideo-DVI v3.0+, but it's vastly better value than this e-waste.
McNutts wrote:The only issue I have had with the HDMI adapter for the GC is that some times the picture drops out for a half second when the resolution switches like when I’m playing Eternal Darkness.
Update to GCVideo-DVI v3.1 to solve this problem with this game, or turn on "Force Video Active" in Swiss.


So GCVideo together with HDMI to YPbPr Converter is worth trying?
Apart from what you’ve mentioned are there any other cons with this route?
You can’t output 240p right?
User avatar
Extrems
Posts: 538
Joined: Sat Jan 30, 2016 5:01 pm
Contact:

Re: Prism component vs OEM component cables for Gamecube

Post by Extrems »

Yes you can output 240p and 480i. You just need to turn off the linedoubler.
Post Reply