"gbisr-ossc.dol" Optimal OSSC Timing via Official Component Cables


This is a quick guide to setting up Extrems's new OSSC-based GBI driver for the Game Boy Player. I'm specifically focusing on GBA playback with absolute best possible picture using the official Nintendo component cables. Below is a line4x scale image resulting from best possible settings in the OSSC using "Metroid Zero Mission":


As you can see, it looks pretty good. However, not exactly perfect. This is because the official Nintendo component cables don't provide a perfectly clean and clear signal, and this results in a bit of 'smearing' to the right of each pixel when the OSSC's dot sample is optimally aligned. During normal gameplay, you're really not going to notice it that much, and you'll otherwise be very happy with the picture quality. For the sake of posterity, here's the difference between component cables and a pure digital rendition of the same pixels:


On the left, you can see the net result of the Component video quality causing that slight smearing effect to the right of each pixel. This is versus a perfectly correct image on the right. As I said, this is as good as it will get with component video on the Gamecube. A person going by the netnick of "Unseen" was however able to reverse engineer the digital output signals from the older Gamecubes that support component output. This has resulted in multiple HDMI solutions being developed and offered for sale online. Theoretically, HDMI should offer 'digital perfect' pixels, and I've ordered one of these devices in order to compare and contrast with official component cables. I will add those results to this article of course when the device arrives.

OSSC Optimal Timing Settings:


Various LPF settings will remain the same from 2x all the way to 5x. The best possible picture resulted from the following settings:

Video in proc )

Video LPF = 9 MHz (SDTV)

Sync opt. )

Analog sync LPF = 10 MHz (med)


For enabling optimal timing:

Output opt. )

240/288p proc:

Set to your desired line multiple (line2x, line3x, etc.)

Once you decide on your linex scale, you'll need to scroll down to the corresponding "LineXx mode" and change its setting to "320x240 optim.". For example:

If you chose your 240/288p proc to be set at "line3x", you'd need to then scroll down to "Line3x mode" and set it to "320x340 optim." Doing this then opens up the proper "(Adv. timing )" sub-menu back in the "Sampling opt. ) menu".


With your scaling choice set, it's time to dial in optimal timing alignment:

Sampling opt. )

Sampling phase = 348 deg

(Adv. timing )

320x240 (this is properly set in the "Output opt. )" menu)

H. samplerate = 433
H. synclen = 31
H. backporch = 49
H. active = 320
V. synclen = 3
V. backporch = 15
V. active = 240


These settings worked great on my Datapath Vision E1S capture card, with the exception of line5x mode. I couldn't get a stable picture when the H. samplerate was set properly to 433. The picture would come back if the H. samplerate was set to an even number like 432, but this knocks the dot sample out of alignment with the graphics. It may just be a quirck of my capture card, and it may work properly on some 4k displays.



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