help question on video propeller

Marc71

Hello!

I have a questions about the PAL CVBS video of the Propeller.

You can have a resolution of 512x384 pixels on TV-out, instead of the vga?

With 2 colors instead of 4?

without having to use a type converter IC MC1377

There is no driver of this type.

Thanks!

Marc71

ericball

Hmm... Is there a reason you picked that resolution? PAL has 625 lines (~576 visible) so 384 doesn't make sense. 512 pixels across might be doable, but not in color as that's far beyond the colorburst frequency. You'd need to disable the colorburst and just just have a black & white signal. I'd recommend having a look at my PAL template (see my sig) as a starting point for developing your own driver.

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Composite NTSC sprite driver: Forum
NTSC & PAL driver templates: ObEx Forum
OnePinTVText driver: ObEx Forum

Marc71

I was wondering can have the same resolution of a Mac Classic, or any Amiga, certainly monochrome, but with that number of pixels H x 512/640 384/240 non-interlaced.

BITMAP course, no character,

Your driver and modified in that way?

Thanks!

Marc71

ericball

No and yes. Because colorburst is not required for a B&W display there is no need for PLLA to be 16x colorburst, so it's possible to use a custom PLLA to get the desired horizontal resolution.

But yes, it can be done. Let me take opportunity to show how.

Okay, you want a simple 1bpp bitmap display. Looking at the comments in my template I see there are 2270*2=4540 PLLA per line (including horizontal blank). 70% of of that (active without overscan) is 3178. So if you want a 512 pixel wide display that means 3178/512 = 6 PLLA per pixel and a total of 3072 PLLA per line. We therefore adjust the VSCL values as so:

vsclbp	LONG	1<<12+(745-397-16*10)+308	'PAL backporch+overscan
vsclactv	LONG	6<<12+6*32	'PAL 6 PLLA per pixel, 32 pixels per frame
vsclfp	LONG	1<<12+309+106	'PAL overscan+frontporch

And then code up the pixel loop:

	MOV	count,#512	'number of WAITVIDs
	MOV	VSCL,vsclactv	'6 PLLA per pixel, 32 pixels per frame
	MOV	outcolor,incolor
	XOR	outcolor,phase	'phasechange
:loop	RDLONG	pixels,pixelptr	'loadpixels
	WAITVID	outcolor,pixels	'outputpixels
	ADD	pixelptr,#4	'increment	pointer
	DJNZ	count,#:loop

In this case incolor is the color for the line rather than a pointer to the colorbar buffer. Initializing VCFG and pixelptr is left as an exercise for the reader.

Marc71

Thanks for the help. ericball!