Help improving the VIC20 palette in vice!

tlr · Post by **tlr** » Tue Nov 18, 2008 8:16 am

From the discussion in these threads: 1, 2.

It would be useful if some of you had the possibility of posting screen-captures (screen grabber is prefered) of the program below.
Please change the PRINT in the first line to identify your machine. VIC20/VIC20CR/PAL/NTSC (and VIC chip information if possible)

I've made a small test program here: palette_bas.prg

As type-in:

Code: Select all

 10 PRINT"{clr}{grn}<INSERT DESCRIPTION>"
 20 A=828
 30 READB:IFB<0THENSYS828
 40 POKEA,B:A=A+1:GOTO30
100 DATA 120,162,17,169,11,172,1,144,200,200,200,200,200,204
110 DATA 4,144,208,251,141,15,144,105,15,202,208,238,240,229
120 DATA -1

It is especially interesting to see if there is a difference between the VIC20 and VIC20CR. For PAL I believe those use the 6561E and 6561-101 respectively.

This is what it looks like in vice:

ral-clan · Post by **ral-clan** » Tue Nov 18, 2008 9:01 am

I wonder if those of us that have tweaked the internal pots around the VIC chip will be disqualified from this...as those tweaks would provide "non-standard" colour level outputs and skew the results of the poll.

tlr · Post by **tlr** » Tue Nov 18, 2008 9:06 am

ral-clan wrote:I wonder if those of us that have tweaked the internal pots around the VIC chip will be disqualified from this...as those tweaks would provide "non-standard" colour level outputs and skew the results of the poll.

I think it will still be useful. Tweaking shouldn't affect the chroma, right?
Also the relative luma levels of the colors should be preserved.
It worth mentioning that you tweaked it though.

ral-clan · Post by **ral-clan** » Tue Nov 18, 2008 9:24 am

It's been a couple of years since I tweaked my VIC for ideal output to a 1701 monitor, but I think that there were two pots - one for luminance and one for chroma. Someone else will have to confirm.

orion70 · Post by **orion70** » Tue Nov 18, 2008 9:55 am

http://sleepingelephant.com/ipw-web/bul ... php?t=1384
http://sleepingelephant.com/ipw-web/bul ... php?p=1349

gklinger · Post by **gklinger** » Tue Nov 18, 2008 10:13 am

Would it help to have a screenshot of the X11 version of VICE running on a Mac or is this one of those WinVICE-only things?

tlr · Post by **tlr** » Tue Nov 18, 2008 10:31 am

orion70 wrote: http://sleepingelephant.com/ipw-web/bul ... php?t=1384
http://sleepingelephant.com/ipw-web/bul ... php?p=1349

Interesting! Confirms that chroma is not affected.
The color test program posted in the second thread will not show all 16 colors simultaneously.

gklinger wrote:Would it help to have a screenshot of the X11 version of VICE running on a Mac or is this one of those WinVICE-only things?

This is one of those real-vic20-only things...
Emulation looks like above on all platforms, what does it look like on real vics?

Boray · Post by **Boray** » Tue Nov 18, 2008 12:43 pm

Every monitor connected to a vic-20 has it's own color nuance. Every PC monitor has it's own color nuance. Every person have set their vic and pc monitors to their own liking with their own choice of brighness and colors. Every digital camera taking a picture of a vic display has it's own color nuance, or many depending on the settings and lights. Every vic chip has it's own nuance. Good luck!

tlr · Post by **tlr** » Tue Nov 18, 2008 2:22 pm

Boray wrote:Every monitor connected to a vic-20 has it's own color nuance. Every PC monitor has it's own color nuance. Every person have set their vic and pc monitors to their own liking with their own choice of brighness and colors. Every digital camera taking a picture of a vic display has it's own color nuance, or many depending on the settings and lights. Every vic chip has it's own nuance. Good luck!

Setting brightness and contrast yes, but usually not color.
On NTSC monitors color can usually be shifted using a tint control though.
These controls are emulated in vice.

What is needed as input is the relative hues and luminances.
Those are hard coded into the chip but subject to process variations.
In the VIC-II used in the c64 the chrominance is very stable due to a clever design.
The relative luminances are quite stable too.
I'm not sure the VIC-I is as stable, but it's resonable to assume the design is somewhat similar.

See here for some info on how it works in the VIC-II: http://www.pepto.de/projects/colorvic/

gklinger · Post by **gklinger** » Tue Nov 18, 2008 2:50 pm

tlr wrote:This is one of those real-vic20-only things...

I completely misunderstood what it was you were asking.

ral-clan · Post by **ral-clan** » Tue Nov 18, 2008 4:07 pm

Boray wrote:Every monitor connected to a vic-20 has it's own color nuance. Every PC monitor has it's own color nuance. Every person have set their vic and pc monitors to their own liking with their own choice of brighness and colors. Every digital camera taking a picture of a vic display has it's own color nuance, or many depending on the settings and lights. Every vic chip has it's own nuance. Good luck!

I think TLR is asking people to frame-grab the output of his/her VIC-20 with a device (like a PCI TV card or DVD recorder or camcorder) that can accept the RCA video output of the VIC-20 directly. Then e-mail that frame-grab to him. I don't think he's suggesting we take a digital camera picture of the monitor.

Boray · Post by **Boray** » Tue Nov 18, 2008 4:18 pm

ral-clan wrote: I think TLR is asking people to frame-grab the output of his/her VIC-20 with a device (like a PCI TV card or DVD recorder or camcorder) that can accept the RCA video output of the VIC-20 directly. Then e-mail that frame-grab to him. I don't think he's suggesting we take a digital camera picture of the monitor.

All A/D converters has their own flavour too

tlr · Post by **tlr** » Wed Nov 19, 2008 1:43 am

ral-clan wrote:I think TLR is asking people to frame-grab the output of his/her VIC-20 with a device (like a PCI TV card or DVD recorder or camcorder) that can accept the RCA video output of the VIC-20 directly. Then e-mail that frame-grab to him. I don't think he's suggesting we take a digital camera picture of the monitor.

Exactly!

Obviously I wasn't clear enough in the initial post, sorry.

If possible I suggest you post the result in this thread, so others can benefit from the data too.

carlsson · Post by **carlsson** » Thu Nov 20, 2008 7:10 am

Unfortunately neither of my computers is equipped for video recording, although I've considered for years to pick up some cheap, perhaps second hand expansion card. Thus I can't contribute at the moment, unless there is a magical way to transform a secondary VGA output to an input device?

Something similar to using a headphone speaker as a el-cheapo microphone.

tlr · Post by **tlr** » Fri Nov 21, 2008 11:28 am

I've made a new program, more suitable for ocular comparison.
It displays all 16 colors sorted according to expected luminance. As you can see some luminances are nearly the same.
Run this on your vic20, turn down the color knob to minimum (i.e bw), and compare to the bw screen shot below.

I can confirm that the luminances on my VIC20 (two-prong, 6561E 4881) are nearly identical to the ones below.

Test program here: palette2_bas.prg

As type-in:

Code: Select all

 10 PRINT"{clr}{grn}<INSERT DESCRIPTION>"
 20 A=828
 30 READB:IFB<0THENSYS828
 40 POKEA,B:A=A+1:GOTO30
100 DATA 120,162,17,169,11,172,1,144,200,200,200,200,200,204
110 DATA 4,144,208,251,141,15,144,189,87,3,202,208,237,240
120 DATA 228,11,107,43,75,139,235,91,171,59,203,155,123,219
130 DATA 187,251,27
140 DATA -1

For the curious: the colors displayed are (top to bottom): 1, 15, 11, 13, 7, 9, 12, 3, 10, 5, 14, 8, 4, 2, 6, 0

This is what it looks like in vice with saturation 0.0:

This is what it looks like in vice with saturation 1.0 (normal setting):