XBOX -> RGB?

[Ed_McCarron]

OK, guess I'll suck it up and ask here.  I guess its -kinda- arcade related.

I need to feed an old Sony projector with RGB inputs.  The PJ will handle sync on green.  Apparently, the XBOX will output RGB -- with a SCART cable.

I'm in NTSC land.  Searching has found a strange point:

"Using RGB negates the differences between NTSC/PAL" -- For some reason, I don't buy this.

Is it as simple as taking one of these:

http://groovygamegear.com/webstore/index.php?main_page=product_info&cPath=66&products_id=231

and splicing BNC connectors in where the SCART end was?

Or, does the SCART cable do funny things to the sync rates on the XBOX?  Theres 3 inputs on the video connector that change the video format...

Every time I think I get my head wrapped around this, I lose it mentally.

Thoughts?  Anyone done this?  Ed, don't be cheap, buy the $11 cable and let us know if it works?

[MonMotha]

NTSC and PAL refer to two things:
1. Video Timing (and this not strictly)
2. Color Encoding

Using RGB for the output option negates the latter (in fact, so does using "conventional" YPbPr component).  The color encoding specifies how you encode the color information onto the subcarrier and is only relevant for composite and s-video.

The video timing is always an issue.  NTSC specifies 525 line (~480 visible) interlaced, 60Hz (well, 59.94 now) video.  PAL specifies 625 line interlaced, 50Hz (exactly) video.  The reason for this is the difference in power line frequency.  There are some advantages in terms of what happens with visual artifacts if things are close to each other like that.  Apparently, early sets also used the AC line as a source of timing.  There are some countries which mix things up.  I believe Brazil uses 60Hz, 525 line video but with PAL color encoding, effectively giving the lower flicker video Americans are used to with the color stability Europeans are used to.

If you're in NTSC land and you get RGB output from your console, you'll have effectively "standard resolution" arcade video: 15kHz horizontal, 60Hz vertical, 480/525 line interlace.  I do this from a PS2 all the time.  If you're in PAL land and you use RGB, you'll get something similar, but 625 line, 50Hz (the line count difference brings you back to 15kHz horizontal), which many arcade monitors will accept as well.

[Ed_McCarron]

Its funny, I think theres an answer in there somewhere, but I can't find it.

So...

I -should- be able to just hook the R, G, and B up and it'll work?

Any idea if the XBOX supports the sync on green standard?

[Silver]

Xbox outputs sync on green.

RGB essentially does make the difference between PAL/NTSC irrelevant, apart from the timing difference described above.

Basically chopping up the scart cable should work just fine. If you are paranoid you can check the input specifications of your projector to ensure it handles 60Hz, but I would be amazed if it did not.

[Ed_McCarron]

Here be specs:

Horizontal Scan Rate:     16 KHz
Vertical Scan Rate:    50 to 60 Hz
RGB Bandwidth:    10 MHz
Screen Size:    70 to 250 inches
Maximum Resolution:    480i

Looks like I'm in!

Thanks!

[Grasshopper]

I'm not sure it's as simple as you guys are suggesting. I've been doing a lot of reading on how to hook an Xbox up to VGA which I assume is similar apart from the higher resolution/refresh rate.

As well as creating separate vsync and hsync signals from the sync on green signal (a simple circuit can do this) you also have to patch the bios to ensure the RGB signals are made VGA compatible. If you don't then the display has a green tinge.

[MonMotha]

If you have a REALLY green tinged image, the output is probably in YPbPr mode, rather than RGB.  This tends to be the default output colorspace for component outputs in North America, while RGB (for SCART) seems more popular on European units.  Many A/V devices which support both output colorspaces, such as the PS2, use the same output lines for both and need to be configured in software.  On the PS2, this is available in the "shell" that you get if you turn it on without a game in the drive.  Many projectors will accept YPbPr in addition to RGB.

Most projectors are smart enough to recognize SOG signals and both sync to them as well as adjust to the fact that blanking is no longer the lowest level on the signal.  If your projector doesn't do this for some reason, you can separate the sync off using something like an LM/EL1881 then strip the sync from the green line entirely to bring it back to syncless video (0V = blank/black, 0.7V = Full Intensity).  If you need to do that, the circuit presented in the datasheet works just fine for getting composite sync.  If you need separate H/V sync, a 74LS86 can be used in conjunction with the LM1881's vertical sync output to generate horizontal sync.

In the end, if you hook the output up to your projector, it's not going to damage it since your projector is spec'd to accept video at the timings the xbox will output.  The only issue would be getting it to see the sync and getting the colorspace right.  My friend and I do this all the time with PS2s hooked up to arcade monitors.  You just rip the sync off the composite video output (since the PS2 does not support SOG) and set the PS2 to RGB in the menu.  In other words, try it and see what happens.  Either it works, or you have some ideas as to what needs to be done.

[Ed_McCarron]

Yup, I'm gonna try it.  If the wiki is correct,

If your monitor supports Sync-on-Green you're lucky - you just need a plain cable to connect your AVIP connector with your VGA monitor. No additional electronic components are necessary.

referring to the xbox... Since my PJ handles SOG, it should be easier to interface than VGA, which is typically not SOG, neccesitating(sp?) the 1881 to seperate sync.

Amazing the crap you learn.   Theres also a setting to adjust individual levels (remember... the PJ is 3 tubes...) so we'll just have to play.

I'll keep informed.