800XL and XE S-video out

[krupkaj]

You are certain remember when I tried to connect my Ataris to LG lcd. Today I have a chance to see S-video out of both machines on oscilloscope. And here are photos of the waveforms

 

XL:

 

and XE:

 

Both machines have original video out. Only chroma signal was added in 800XL. The upper waveform is chroma lower luma. On the screen was Basic interpreter with some lines of text. So what are you thinking about that?

Edited December 8, 2007 by krupkaj

[Rybags]

I don't think the waveforms themselves are the actual problem.

 

See my thread I did a couple of weeks ago about the 240 scanline hires mode http://www.atariage.com/forums/index.php?showtopic=116930 - although it's not really directly related to this, but kind of the same subject.

 

I think the problem with LCDs is not that the waveforms themselves might be a bit "out of spec", but the fact that the Atari (and most other 8-bit era machines) don't produce interlaced video.

 

Rather than the PAL standard of alternating frames of 312/313 scanlines the Atari produces the same 312 line frame, resulting in the interlaced effect we all know (with every second line blank).

 

Since LCDs and video capture cards have internal logic which pre-processes video before displaying it, they can get "confused" and some models just can't handle the display.

 

 

How about trying something like the static logo from a DVD player? Then, setup the Atari again (make it's screen colours the same and just put some text on the screen to approximate the DVD player).

 

Then try and capture both. The important bit you'd probably want to get is the dozen or so scanlines around VBlank time.

[+bob1200xl]

Are these the waveforms of the working machines or the ones that do not work? You should have something like 0.3 volts of CHROMA and 0.7 volts of LUMA. I would guess that the monitor/TV has to normalize the signal and then pick out the sync timings. If the voltages are too high, the circuits will clip them off. Where is the DC level on these signals?

 

Bob

 

 

 

You are certain remember when I tried to connect my Ataris to LG lcd. Today I have a chance to see S-video out of both machines on oscilloscope. And here are photos of the waveforms

 

XL:

 

and XE:

 

Both machines have original video out. Only chroma signal was added in 800XL. The upper waveform is chroma lower luma. On the screen was Basic interpreter with some lines of text. So what are you thinking about that?

[jacobus]

Since LCDs and video capture cards have internal logic which pre-processes video before displaying it, they can get "confused" and some models just can't handle the display.

This might explain the issue I'm having connecting an XEGS to a LCD TV. Using either the RCA or SVideo (+adaptor) in, I get a very clear display that flashes on and off every second or two. Maddening really. The coax works, but the display is too fuzzy.

 

Is there anything I can add to the XE's signal to make it more palatable to the LCD? Or should I just give up on that screen and go looking for a compatible one?

[Rybags]

I tend to think it might be the old "non-interlaced" problem again.

 

Does it do that if you have only the luma connected (a valid combo, since luma carries sync as well).

[jacobus]

I tend to think it might be the old "non-interlaced" problem again.

 

Does it do that if you have only the luma connected (a valid combo, since luma carries sync as well).

ummm ... I think I'm lost here. How can I remove chroma from the equation (using the RCA composite connection?). The SVideo connection that I talked about is an adapter that goes from RCA composite to some multi-head cable that came with the TV (svideo, composite and audio) and then into a special socket on the TV. Short of cutting wires I'm not sure what I can do to modify that connection.

 

That being said, I still get the same blinking behavior regardless of whether I go directly in through the composite (the TV has a direct RCA in) or if I use the hydra cable.

Edited December 12, 2007 by jacobus

[Rybags]

Get seperate luma/chroma by using the monitor port.

 

Would involve some work soldering up a plug though.

[jacobus]

Get seperate luma/chroma by using the monitor port.

 

Would involve some work soldering up a plug though.

Is this something that the "Super Video" upgrade would enable/address?