Getting best possible RGB picture out of PS1

[Medis]

Jeez my bad I forgot to include that video,

https://www.youtube.com/watch?v=U0Eik1407dQ

Sorry for my really creepy english, i kept forgetting to breathe .
Its not all that visible on phone i recorded with but it adresses some stuff.
Also i didn't fully wrote the subtitles if case its not understable

[rama3]

Well, the sound buzz is definitely a bad RGB cable. If your cable was 10 bucks from Ebay, it is bad ;p
RGB cables require good shielding, which is expensive, which is why you never see a good cable on the "regular" aftermarket.
Your options are:
- build one yourself
- buy from a specialized cable maker
- find an original Sony cable

[Medis]

Allright,

But how about the off-screen aka out of center screen? On TV in that Video its not as much as on other TV's.
It occurs on C-Sync, Sync-on-Luma but not on an original pin 6 - Sync-on-Composite (aka Vsync).

Also I think that this discussion is a great gathered collection of informations that may be handy for everybody hehe.

[TheShadowRunner]

The slight horizontal position shift when using RGB versus composite is completely normal and happens with all consoles, don't worry about it.

[rama3]

Maybe the TV has some kind of menu setting for image position correction. It could be hidden in a service menu as well.
To reach it, you'll have to find the service manual for the TV.
It's usually activated by turning the TV on with some button combination pressed. Other times it requires a special code from the remote.

[Medis]

Guys... you seem to be right...
My C-Sync mod was always done well... its the cable what is causing different interference on different TV's...
It was driving me crazy... heh...

Anyway!
The original PS RGB cable costs ... way too much, in auctions on ebay...
I could live with different one if its good shielded one...

http://www.ebay.com/itm/6ft-For-Sony-Pl ... OSwCypWmOD~

So how abou this? Thick cable = no shielding, Fat cable = Magnetic Shielding!
Thats the theory, but there heck ,lets hope its full-connected without missing wires.
Ill try to win auction for sony's one.

[clavicus]

I'm actually having a stab at making an HDMI mod for the ps1, while I'm waiting for my minispartan3 to arrive I hooked up a logic analyser to the GPU and SPU to get a better picture, and I already have some issues:

• I'm measuring 2.706 MHz for PAL and 1.357 MHz for NTSC for the pixel clock via pin 199 of the GPU, which doesn't make much sense as that's not nearly enough for 320x240. The fact that the NTSC clock is exactly half of the PAL one is even more confusing, but I'm pretty sure I have the right pin. The vblank and hblank signals are fine.

• The bitstream audio data signal from the SPU is a little elusive, because I have a PU-22 and the DAC is integrated. Pin 155 (DATO) was the first obvious choice given its proximity to LRCO and BCKO, but it's either not connected or pulled low. Pin 158 (DTIB) is useless as it's input-only from the parallel port. I then tried pin 14 (DOUT) and there's definitely something there, and it's also next to LRCK which is the same clock as LRCO (44.1 kHz). I'll need to try a cd with a fixed tone or something to make sure.

[Medis]

Perhaps burning a WAV audio CD with "sinewave" generated in audiocity?
It should take 5 mins to make it done.

It's great to see someone skillfull work on it!

[rama3]

If you have a Ceatla extension cart, you can use the RAM viewer function to quickly change through some common resolutions / pixel clocks. You should definitely get something more around 5 or 6Mhz.

Code: Select all

Horizontal Timings

  PAL:  3406 video cycles per scanline (or 3406.1 or so?)
  NTSC: 3413 video cycles per scanline (or 3413.6 or so?)

Dotclocks:

  PSX.256-pix Dotclock =  5.322240MHz (44100Hz*300h*11/7/10)
  PSX.320-pix Dotclock =  6.652800MHz (44100Hz*300h*11/7/8)
  PSX.368-pix Dotclock =  7.603200MHz (44100Hz*300h*11/7/7)
  PSX.512-pix Dotclock = 10.644480MHz (44100Hz*300h*11/7/5)
  PSX.640-pix Dotclock = 13.305600MHz (44100Hz*300h*11/7/4)

[clavicus]

All's good, I didn't have my cheapo chinese analyser sampling frequency high enough It can't handle 24 MS/S for very long so I usually keep it lower.

Booted an NTSC game and get 6.639 MHz which is correct. If my hunch is right about the audio bitstream then I have everything I need...in theory. But that was the easy part, massaging the bits into HDMI is going to take some work, luckily there seems to be enough info online and in the spec.

[Medis]

So I don't have to buy those expensive as *uck upscalers but rather wait :3 ? Because that would be total victory

[clavicus]

That will depend on your soldering skills, if and when this is complete it will need 30+ wires, with at least one needing to be soldered directly to an SPU pin unless I can find an alternative. You'll also need to consider that FPGA dev boards with HDMI aren't super-cheap at $50-ish.

[Medis]

awesome, I think I can do that, It is still cheaper <!> than getting shielded cable n upscaler

[rama3]

Clavicus, for an initial proof of concept, do you think it'd be enough to connect just one bit per RGB channel (and the rest of the timing stuff, of course)?
Such a project would definitely teach me stuff. I'd like to try it!

[clavicus]

Yeah that will definitely work for testing, but I don't even have any code ready right now. As soon as I get at least the video working I'll share the code.

[nocash]

Jeez my bad I forgot to include that video,
https://www.youtube.com/watch?v=U0Eik1407dQ

That isn't a public link (youtube is prompting to sign-in by entering your email or phone number).

The slight horizontal position shift when using RGB versus composite is completely normal and happens with all consoles, don't worry about it.

I've never thought about that, but it makes sense... if the composite encoding/decoding takes some extra time, then composite picture would be moved towards right, or the other way around: RGB picture would be moved towards left?
How much is that position shift for different cables, with same sync signal, on the same TV? I guess it can't be more than 1-2 pixels (at 320pixel resolution)? Ie. nothing that would make certain games totally unplayable with RGB cables.

[Medis]

I closed the video on purpose,

[TheShadowRunner]

I've never thought about that, but it makes sense... if the composite encoding/decoding takes some extra time, then composite picture would be moved towards right, or the other way around: RGB picture would be moved towards left?

So that's why! I've always wondered why the slight difference. Yes your explanation makes perfect sense, and indeed RGB picture is slightly moved to the left versus composite.

How much is that position shift for different cables, with same sync signal, on the same TV?

Not sure I get this question..
But with the same cable that's built for both composite and RGB, on the same TV, and using the different TV inputs to display either RGB or composite, I would say there's more than 2 pixel shift, more like 5-10 it seems to me.

[nocash]

Whoops, 5-10 pixels is quite huge. And considering that different TVs tend to have the screen centering adjusted differently, it might well sum up to even more pixels being cut-off at the screen sides. Quite a pity that the psx kernel doesn't provide an option for calibrating the screen-centering.

[rama3]

The problem was common in analog TV days. Many games include a picture positioning feature because of it.
It's best if this can be adjusted on the TV itself.
My Sony retro tube has offset controls in 3 different places. Just shows how common centering issues were then :p