3DO 240p output - VP536A encoder

Glad to hear it!

If it wasn't 330am I would actually throw a video up right now. I'll probably do one tomorrow evening though. I'll post up some direct captures in here as well I'm case anyone wants to see them.

Thanks again! So glad to be rid of that awful 480i.

 

If you want it to be 240p at all times, you could rig something up to drive the line high after a delay.

 

I'm going to have to pop open my fz-10 when I get home and hope it has the VP536A

 

If its not too much trouble you should try booting into 240p and see what happens. I'm curious if its just something on my end, or if the fz-10 has to boot into 480i before being able to switch to 240p.

 

I also have an Fz-10 that ill try this mod out on, provided it has VP536A.

 

So one thing I realized after coming home and messing with it a bit more. When you flip the switch to 240p mode you can actually lock it on the incorrect line update. If that happens you just flip it again while its running and you should lock the correct one in maybe 2-3 trys at the most. Ive actually only done it a few times, but hooked it to my pvm to verify that was what was happening(xrgb blacks out during resolution changes so it was hard to pinpoint what was happening). I ended up putting a closed push button in so I just hold it while I boot it, and if I miss the correct line update I just press it again.

I'm going to post a couple of pictures of 480i, and both line refreshes of 240p so you can see what it should look like.

It makes it sound harder than it is, and honestly, this looks and works beautifully.

 

Hopefully these images will work. All of these are running through an XRGB Mini upscaling to 1080p.

480i

240p (correct line update)

240p (incorrect line update)

 

Wow, the rgb stills really show how blurry 480i is! Interesting about the incorrect line update - I haven't seen that happen on my Goldstar.

Have you had time to do a 60fps capture for YT?

 

I would think if you can boot the goldstar directly into 240p it begins on the correct line so you shouldn't have to worry about it. If youre able to switch while its on you can probably get it to lock to the wrong line. Easiest way to tell is the title screen on super turbo. The word turbo has a clear line around the top of it. If you manage to get the incorrect one it has some lighter outline around it.

Im actually uploading a video right now. I'll post the link once its up. Didnt realize how few 60fps games were on the 3DO. Even Samurai Shodown is 30fps : )

 

RGB 3DO Capture - 240p Mod - XRGB Mini - 1080p - 60fps: http://youtu.be/yaewko8OR8c

 

This mod doesn't affect how the 3DO renders its video internally, it merely tells the encoder whether to interlace Vsync every other frame. In other words the encoder will always receive 480i video, if that's how the 3DO is designed.

Forcing 240p will lead to jitter problems when you come across a game that actually renders interlaced frames to increase the vertical resolution. It's my feeling that most 3DO games are extremely lazy, and I've seen a lot of "screen tear" when games scroll--so it might be that the majority do (asynchronously) draw 240 line frames field by field.

Regarding the physical mod, VAA is the analog supply for the DAC. This is intended to be a "clean" supply--free from switching noise, so you shouldn't connect it to a digital pin which inherits noise via clamp diodes from the VDD rail. Use VDD directly. Also you don't need to wire a signal high through a resistor*, that hasn't been necessary since very early TTL chips and the 3DO is built on "modern" CMOS.


*If the FZ-10 controls this signal (unsure from reading this thread) it would be a good idea to insert a series resistor (10k) between the ASIC output and encoder pin so that when you force 240p there is minimal stress on the ASIC.

 

The 3DO's frame buffer is 320x240, it isn't up to games to render interlaced frames.

Thanks for the info on VAA - what would be a better place in the 3DO to obtain voltage to set the pin high?

 

Is there a reliable source for that?

 

I am referencing the 3DO SDK docs. Some (all?) are availalble online.

Frame Buffer
Introduction to 3DO Graphics Systems
Display Generator
Controlling interpolation

I'm not sure, but I believe what we are doing when we set pin 52 high is turning off interpolation within the Display Generator (in this case the VP536A). This can also be done through software with two lines of code, as seen in the last link:

int32 DisableHAVG( Item screenItem )
int32 DisableVAVG( Item screenItem )

I'm not sure why no 3DO games used this mode - perhaps developers simply overlooked it. Or perhaps they were as you said, lazy

 

Indeed it looks much clearer/crisper than your previously captured 480i video, thanks for putting that up! The 58p flag is interesting..

 

I don't suppose there's any chance of this happening on the later FZ-10 models with the combined video and sound encoder ("Anvil") I couldn't get the RGB mod done because there is virtually no documentation on the Anvil chip.

 

Am I missing something... I see where you are activating the 240p by adding voltage and activating it, but where are you getting the RGB lines from to go to the Scart cable or composite lines?

 

240p is being output over svideo in my case. I'm working on enabling RGB output with the BU3616K chip.

 

I completed the RGB mod using a BU3616K DAC. Here are some comparison videos:

240p S-Video vs 240p RGB: http://youtu.be/yYJPTqI8yME

480i RGB vs 240p RGB: https://www.youtube.com/watch?v=BUmOzoLNdUI

 

Fun story, I wired up a switch on my FZ-10, since it needs to be disconnected during boot. Been playing a few games in 240p, then I tried Wolf3D. Turns out, with 240p enabled, the enemies in the game are twice as fast! Was confused for a solid 10 minutes why they were so fast, thought it was something with the difficulty setting. Flipping the switch off during game made them normal speed again. Must be something with the game speed tied to 480i..