PSone ypbpr modification

Graphic based area of development (Graphics Processing Unit), including the Geometry Transform Engine (GTE), TIM, STR (MDEC), etc.
Post Reply
vulpusotaku
What is PSXDEV?
What is PSXDEV?
Posts: 3
Joined: August 26th, 2017, 5:58 am

PSone ypbpr modification

Post by vulpusotaku » August 26th, 2017, 6:07 am

So I was recently looking for a project and remembered that the PSone supports RGB. I remembered that the SNES also supports RGB and people have modded that to use ypbpr. So I looked up and found out that it's pretty close to possible, but unfortunately I've only been able to place c-sync on green but have no green signal. The image is relatively stable but it's all pink do to no green.

Please respond with help and don't tell me "PSone don't support component". I already know, I'm trying to mod it

Images
https://drive.google.com/file/d/0Bw5oGj ... sp=sharing
https://drive.google.com/file/d/0Bw5oGj ... sp=sharing
https://drive.google.com/file/d/0Bw5oGj ... sp=sharing
https://drive.google.com/file/d/0Bw5oGj ... sp=sharing

I know I'm using a GBS 8200 but my tvs that support 240p get the same result.

User avatar
Someone
Curious PSXDEV User
Curious PSXDEV User
Posts: 17
Joined: August 7th, 2016, 11:40 pm
I am a: ROM hacker hobbyist
Want to Find: Interesting info about PS1

Re: PSone ypbpr modification

Post by Someone » August 26th, 2017, 5:02 pm

LOL, you just shorted green to the ground. Don't you see it on 4th photo?

vulpusotaku
What is PSXDEV?
What is PSXDEV?
Posts: 3
Joined: August 26th, 2017, 5:58 am

Re: PSone ypbpr modification

Post by vulpusotaku » August 27th, 2017, 3:36 am

It's not, Can't you see the gap between 12 and gnd?

If it was I wouldn't get any kind of sync.

User avatar
Someone
Curious PSXDEV User
Curious PSXDEV User
Posts: 17
Joined: August 7th, 2016, 11:40 pm
I am a: ROM hacker hobbyist
Want to Find: Interesting info about PS1

Re: PSone ypbpr modification

Post by Someone » August 27th, 2017, 7:37 am

You surely don't know what you're doing there. You didn't isolated that resistor's wire so it touches exposed copper on the PCB.

rama3
/// PSXDEV | ELITE ///
/// PSXDEV | ELITE ///
Posts: 472
Joined: April 16th, 2017, 10:54 pm

Re: PSone ypbpr modification

Post by rama3 » August 27th, 2017, 10:09 pm

As far as I know, you need to transcode the RGB. Simply injecting a sync signal will get you a picture, but it'll be all wrong.
Transcoding means adding extra hardware and aparently it's quite difficult to do.

vulpusotaku
What is PSXDEV?
What is PSXDEV?
Posts: 3
Joined: August 26th, 2017, 5:58 am

Re: PSone ypbpr modification

Post by vulpusotaku » August 31st, 2017, 11:12 am

I asumed I would need extra hardware. I was hoping to use the lm1881, but how I wired it, didn't work.

rama3
/// PSXDEV | ELITE ///
/// PSXDEV | ELITE ///
Posts: 472
Joined: April 16th, 2017, 10:54 pm

Re: PSone ypbpr modification

Post by rama3 » August 31st, 2017, 8:08 pm

You need to convert all 3 RGB signals as well.
Ypbpr reduces RGB+S (4 wires) video into RGsB (3 wires, sync is now on G) using a formula.
Video encoder chips do this, such as the one in an SNES (but there are other, more modern chips).

Wiring up such a chip is tricky but doable with some experience.
But the sync part can be hard to get right. It should get added to green, as a 0.3V 'negative' / below black level signal.
That causes some issues when the input signal is too weak, too strong or otherwise unfit for the encoder.
You would get a full color picture, most likely, but it could be washed out or too bright / dark.

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest