The optimal VICE PAL VIC aspect ratio

Boray · Post by **Boray** » Mon Apr 12, 2010 7:37 am

In VICE 2.2, you can set a fix aspect ratio in Settings/Video settings/Keep aspect ratio. The default is quite dreadful...

Well, I measured the Vic-20 output on a LCD TV (set to 4:3 display). I then tried to get the exact same aspect ratio on my computer's LCD monitor. I came up with a setting of 0.809

I'm using it windowed with double size and PAL emulation and it looks really nice.

Has anyone else done the same thing?

Pedro Lambrini · Post by **Pedro Lambrini** » Mon Apr 12, 2010 7:42 am

Well, I didn't measure anything but just by eye I ended up adjusting it to .833. First, I set it to .800 and then threw in another bit for good luck. It became .833 rather than .830 because I hit the 3 key twice by accident on my flaky keyboard... Pretty close if I say so myself!

orion70 · Post by **orion70** » Mon Apr 12, 2010 9:32 am

I followed tlr's suggestion and .825 looks just fine for me

.

Schlowski · Post by **Schlowski** » Mon Apr 12, 2010 10:19 am

I just measured on my Philips CM-8833 monitor and checked against VICE and came up with 0.810. Looks great now, similar on VICE and on the real monitor, thanks for the hint!

Post by **Jeff-20** » Mon Apr 12, 2010 7:46 pm

Should we change the emulator on the front page?

Bacon · Post by **Bacon** » Mon Apr 12, 2010 11:55 pm

Pedro Lambrini wrote:Well, I didn't measure anything but just by eye I ended up adjusting it to .833. First, I set it to .800 and then threw in another bit for good luck. It became .833 rather than .830 because I hit the 3 key twice by accident on my flaky keyboard... Pretty close if I say so myself!

I did the same thing, although I didn't fine-tune it very much. I tried 0.900 (too wide), 0.700 (too narrow), and finally ended up with 0.800.

Pedro Lambrini · Post by **Pedro Lambrini** » Tue Apr 13, 2010 3:17 am

Jeff-20 wrote:Should we change the emulator on the front page?

If it's easy enough why not?

OT: what are the chances of your games being added to the emu, Jeff?

Boray · Post by **Boray** » Fri May 14, 2010 3:37 am

Has anyone done something like this for the other VICE emulators? The C64 for example?

darkatx · Post by **darkatx** » Mon Feb 25, 2013 2:15 pm

I'm having a major issue with screen caps - I'm wondering why my screencaps are being stretched by my Nvidia card. The aspect ratio in my actual display is perfect (0.84)...I tried every variation of Video Option in VICE but my screencaps are all stretched horizontally? Anyone having a similar issue with this?

Mike · Post by **Mike** » Mon Feb 25, 2013 3:59 pm

I suppose you're referring to the menu option 'Snapshot > Save/stop media file ...' in VICE. In that case, this has nothing to do with your graphics adapter card. VICE always saves the screen buffer contents before any filters (such as rescaling and TV system emulation) are applied. And this screen buffer happens to use a 2:1 pixel aspect ratio.

If you want the filtered output, highlight the VICE window, use Alt+PrntScrn (this will just put the window in focus into the clipboard), and then paste the clipboard data into the image viewer of your choice.

I actually prefer the unfiltered output, because I then can apply filters of my own choice.

darkatx · Post by **darkatx** » Mon Feb 25, 2013 4:17 pm

That's what I've been doing as an alternative (print screen and paste into a viewer)...cool never knew about the screen buffer 2:1 ratio...makes total sense now.
Thanks Mike

Mike · Post by **Mike** » Mon Feb 25, 2013 5:00 pm

This 2:1 ratio (i.e. simple pixel doubling) was what VICE always used for display until around version 2.1 when fractional pixel aspect ratios were introduced. Of course that value of 2:1 had been totally off.

It still leaves its marks because one still specifies the pixel aspect ratio within VICE in ratio to this pixel doubled screen.

You actually get a real pixel aspect ratio of 1.666:1, when you specify 0.833 (what I happen to use for PAL, btw.)

darkatx · Post by **darkatx** » Mon Feb 25, 2013 5:28 pm

I honestly thought that the True Aspect ratio of .84 was a close enough approximation of it so I didn't complain but putting it 'to the thirds' made a noticeable difference

Wow, it looks proper now - even to my eyes - it looked true right away!!!

Mike · Post by **Mike** » Thu Feb 28, 2013 4:11 pm

Hmm? I was under the impression, that NTSC had a different pixel aspect ratio more like 1.5:1 (which would correspond to 0.750 in VICE).

I got my value a long time ago by measuring the width and height of the text window of the VIC-20 on a TV set, which had been confirmed before to draw perfect circles with a standard test image of a broadcast station. The text window has 176 pixels width and 184 pixels height.

I don't remember the exact measurements, but the calculation went similar to this example:

Width: ~44 cm
Height: ~27.5 cm

Now, a single pixel has a width of (44/176) cm and height of (27.5/184) cm. Dividing the width of the pixel by its height gives the pixel aspect ratio thus:

Code: Select all

  44      27.5     44   * 184
------ / ------ = ------------ ~= 1.67
 176       184     27.5 * 176

... which is surely not more accurate than 2 digits after the decimal point.

Finally, I approximated this value of 1.67 with a fraction using small integers in numerator and denominator, and came up with 5/3 = 1.666...

darkatx · Post by **darkatx** » Thu Feb 28, 2013 8:45 pm

Either my eyes deceive me and my recollection of my TV days isn't what it used to be. I could be wrong...wouldn't be the first time

(EDIT) Did some double-checking (took the screencaps and did some overlays) and yup...I am way off and 1.5:1 is indeed correct.