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Author Topic: Ep128 display on a crt TV (Read 4369 times)

Offline ssr86

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Ep128 display on a crt TV
« on: 2015.October.18. 19:04:35 »
On my old and small tv:
- I see only about 336 pixels in width and the screen is shifted one character to the right
- I see only about 256(?) pixels in height - starting from the 16th line (from a 288 line screen)

Is this normal or is it just my tv?

That would mean that ep has considerably bigger pixels than the c64 (on the ep I have no place for the c64's side borders), I guess...
« Last Edit: 2015.October.18. 20:02:37 by ssr86 »

Offline Z80System

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Offline ssr86

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Re: Ep128 display on a crt TV
« Reply #2 on: 2015.October.18. 19:20:17 »
Thanks for the links.

I wonder what is the reason for such "magnified" and shifted display...
Well the TV was broken many times before...

However I remember reading in the nick doc:

"10. Vsync Mode - Vertical Synchronisation
[...]
These LPBs make a total of 25 lines, leaving 287 lines left for the display. In practice, because of overscanning, it is not possible to use more than about 256 of these for display, the rest must provide top and bottom borders. "

So is there a problem with displaying screens of vertical resolutions bigger than 256 or there's nothing to worry about?

Offline Z80System

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Re: Ep128 display on a crt TV
« Reply #3 on: 2015.October.18. 19:37:21 »
From the perspective of the EP's display chip there is no problem to generate pictures with size approximately 368 X 272. (Meaning of the "standard" HIRES 4 colour pixel size.)

There will be people here who can say the numbers more precisely and theoretically (I only got these numbers with experiments with the values in real programs.)

There will be TVs and monitors (mostly TVs) of course, what cannot sync to these values, or at least they will show some less pixels in width cutting the two side on the left and the right.

That is not an exact value of the displays. Probably it is not in the standards, or maybe TV picture is less and not every TVs supports the bigger width.


But your values are (as far as I know) far less than the usual values.
« Last Edit: 2015.October.18. 19:45:33 by Z80System »
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Offline Z80System

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Re: Ep128 display on a crt TV
« Reply #4 on: 2015.October.18. 19:43:13 »
Generally we can say (I think) that every monitor and TV sould display the size of the 320 X 240 (with HIRES 4 size of pixels) WITH some border ...

It is basically for example the IS-BASIC screen.

If your TV cuts the BASIC screen or there is no border around it,
then your TV shows too less, far less than generally.

You can set the border on the BASIC screen like:

set border 255
« Last Edit: 2015.October.18. 19:47:52 by Z80System »
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Offline ssr86

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Re: Ep128 display on a crt TV
« Reply #5 on: 2015.October.18. 20:08:02 »
Generally we can say (I think) that every monitor and TV sould display the size of the 320 X 240 (with HIRES 4 size of pixels) WITH some border ...

It is basically for example the IS-BASIC screen.

If your TV cuts the BASIC screen or there is no border around it,
then your TV shows too less, far less than generally.
Then the main(?) problem with my TV would be the one charcter shift to the right, as it cuts some of the is-basic screen. The visible side border is about 16 pixels in total.
Vertically it would be around 240 lines so I guess the TV satisfies the general criteria.

Offline Z80System

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Re: Ep128 display on a crt TV
« Reply #6 on: 2015.October.18. 20:51:48 »
Quote
Vertically it would be around 240 lines so I guess the TV satisfies the general criteria.

In this case ... Yes.

But (of course) the wider is the better ...

There are screens of tools and demos (maybe games aren't but only one or two) and such using larger screens.

For example now I write a thing, using 368 X 272, and I would not like to be smaller,
because I use LORES 4 and doubled vertical scanlines,
so the effective resolution of my game will be as little as 184 X 136 ... at the same physical size on the display.

So if I were decreese the size of the screen, my resolution would be even smaller ...
So the screen stays the biggest possible what displays usually shows ...
And that is the 368 X 272 (with the standard pixel size, again) ...

It is bigger than the "must display" size, but the "not limited" displays usually display this big screens ...

Above this, there are a few TVs what show the screen without cutting ...



The EXOS doc says about NICK:

http://gafz.enterpriseforever.com/Dokumentacio/Konyvek/EXOS_2.1_technikal_information/hardware/Nick.html

"allowing up to 42 characters per line", what is 42* 8= 336 (HIRES 4 pixel) wide ... :)


What is far below the 368 I use in my game ... :) Maybe we just found the reason why my game does not run on the real steel ... ?! :)
« Last Edit: 2015.October.18. 21:17:28 by Z80System »
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Offline IstvanV

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Re: Ep128 display on a crt TV
« Reply #7 on: 2015.October.18. 20:53:02 »
That would mean that ep has considerably bigger pixels than the c64 (on the ep I have no place for the c64's side borders), I guess...

It is normal that the pixels are wider than on the C64, but the height should be about the same:

EP: 57 characters per line at 889846 Hz (15611.33 Hz horizontal sync frequency)
C64 (PAL): 63 characters per line at 985248.6 Hz (15638.87 Hz horizontal sync frequency)

EP pixels are closer to square shape (in 4-color PIXEL mode), on the C64 they are narrower.

Quote
- I see only about 336 pixels in width and the screen is shifted one character to the right
- I see only about 256(?) pixels in height - starting from the 16th line (from a 288 line screen)

These are not unusual on a TV, although the screen is more commonly shifted to the left by one character.
« Last Edit: 2015.October.18. 20:56:13 by IstvanV »

Offline ssr86

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Re: Ep128 display on a crt TV
« Reply #8 on: 2015.October.18. 21:14:15 »
These are not unusual on a TV, although the screen is more commonly shifted to the left by one character.
Ugh:oops: ... It's "shifted to the left"....
I'm almost 30 and still have problems distinguishing right from left..:lol: .

Offline Z80System

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Re: Ep128 display on a crt TV
« Reply #9 on: 2015.October.18. 21:22:42 »
Quote
What is far below the 368 I use in my game ... :) Maybe we just found the reason why my game does not run on the real steel ... ?! :)

No. 46 character is a real width. I found 46 in the forum at many places. Expert ones say too, 46 (*8= 368 pixel) is possible from the side of the NICK.

Only the displays can make it cutted ...

(A big rock came off from my heart ... how the hungarian people say ...)
« Last Edit: 2015.October.18. 21:26:04 by Z80System »
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Offline Z80System

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Re: Ep128 display on a crt TV
« Reply #10 on: 2015.October.18. 21:34:07 »
Quote
EP pixels are closer to square shape (in 4-color PIXEL mode), on the C64 they are narrower.

Maybe was this because of the quality of the CRTs from that age ?
I noticed on all of my CRTs, that pixels are wider than their height (in HIRES 4, too) ... Maybe the C64's pixels arent as wider, because of this trick ?
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Offline ssr86

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Re: Ep128 display on a crt TV
« Reply #11 on: 2015.October.18. 21:49:44 »
Maybe was this because of the quality of the CRTs from that age ?
I noticed on all of my CRTs, that pixels are wider than their height (in HIRES 4, too) ... Maybe the C64's pixels arent as wider, because of this trick ?
I remember running my game wip for the first time on the real machine and noticing/thinking that the pixels aren't square but somewhat a little wider (also compared to the emu)...

Offline Z80System

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Re: Ep128 display on a crt TV
« Reply #12 on: 2015.October.18. 21:54:21 »
Quote
running my game wip

Can I see a screenshot somewhere about it ? (Beacuse of the game, not because of the pixel width ... :))
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Offline IstvanV

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Re: Ep128 display on a crt TV
« Reply #13 on: 2015.October.18. 22:13:19 »
It probably depends on the CRT, with a TV capture card that seemed to be reasonably accurate with standard TV input I found that the output of the NICK is 3.9% wider than perfect square pixels (532 instead of 512 on this picture), so extrapolating from that the C64 would be about 6% narrower. On other devices, the C64 could be closer to square pixels. :)
« Last Edit: 2015.October.18. 22:17:41 by IstvanV »

Offline ssr86

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Re: Ep128 display on a crt TV
« Reply #14 on: 2015.October.18. 22:16:03 »
Can I see a screenshot somewhere about it ? (Beacuse of the game, not because of the pixel width ... :))
https://enterpriseforever.com/programming/pixel-artist-wanted/

old wip video: https://www.youtube.com/watch?v=5Qb3tiWqjtU