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Author Topic: Crtemudriver + composite encoders  (Read 457 times)

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retrorepair

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Crtemudriver + composite encoders
« on: February 13, 2018, 06:34:41 pm »
So I'm a bit weird in that I want the option to encode rgb from my pc using crtemudriver to composite video but I'm having issues getting it to work.

I've tried two different encoders (totally different chips) and in PAL mode neither seems to work with the output from crtemudriver. One encoder was selectable pal/ntsc output and the other was just pal. I've tried on both my mx7000 tv and a sony pvm. The tv outputs a weird half flickery half incorrect colour picture and the pvm is just black and white.

The pvm detects and displays ntsc resolutions correctly (as does the mx7000) with the encoder set to ntsc and tells me it's found an ntsc signal but if I switch to pal it says it's found an ntsc433 signal in some pal resolutions.

As far as I was aware the rgb signal should just differ on the vertical refresh and number of lines used but obviously theres something else going on. I thought the only difference between pal and ntsc composite video was the colour system they used?

I've tried the pal tv preset in vmmaker and it doesnt make a difference, any ideas whats going on?

Sorry if I'm not explaining myself very well!
« Last Edit: February 13, 2018, 08:58:49 pm by retrorepair »

buttersoft

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Re: Crtemudriver + composite encoders
« Reply #1 on: February 13, 2018, 10:48:08 pm »
Out of interest, what happens when you deliver a 50Hz 15kHz mode to the encoders but leave them on NTSC?

If these are cheapo Ebay encoders with VGA inputs, i would guess they are not designed for 15kHz input - and you're lucky they work at all. Does the same thing happen when you test a normal 31kHz+ PC video mode only at 50Hz?

If they don't take VGA, what input do they take and how are you combining sync? If they are designed for 15kHz input, test the RGB from a console like a PAL PS1 (or a chipped PS1). It might be that they aren't built to handle 5V TTL sync?

retrorepair

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Re: Crtemudriver + composite encoders
« Reply #2 on: February 17, 2018, 06:50:59 am »
You were right, the sync was the issue, just needed to add voltage dividers to the h and v sync and PAL mode works great now!

  
 

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