APAC 256 color mode 80x240 'interlaced': has this been done?

[bugbiter]

I wanted to do this since the 80s...

 

In all those topics about APAC modes I only ever see the 'static' mode with 96 lines Gr.9 (lumina) and 96 lines Gr.11 (chromina).

I always hated the dark lines and the resulting low vertical resolution in that mode.

 

So I swap the Gr.9/Gr.11 lines in every VBI, showing a picture with full vertical resolution of 240 lines(239 really because of the 240 line bug).

I dont think the flicker is so bad, it just reminds me of an ordinary interlaced tv picture.

 

What do you guys think about it?

 

Actually, it works fine with NTSC on my 1200xl - I always thought you need PAl to blend the line colours on a crt.

 

 

I always wanted to be able to see my own photographs on the good old atari.. I therefore wrote a converter for windows BMP pictures in basic.

On atari800Win Emulator in warp mode conversion of one picture with dithering takes 3 minutes.. :-)

 

I've read about this mode but I've never seen it anywhere. If it is already here somewehere you may well bash me about it :-)

 

Its so great having all the tools and emulators these days, makes coding and debugging for the atari so much more effective and fun!

I really enjoy coding like in the old days but now with every resource and information available to me. I didn't have that in the old days...

 

The disk starts the autorun.bas file automatically. after the memory overview press any key to start initializing the Display List and the LMS adresses.

You can then choose the picture file with the cursor keys of a real atari, meaning up and down on an emulator would be "-" and "=".

Only two pictures fit on the disk, sorry.. they're each 19KB after all!

Return loads the file.

 

Greetings,

Martin

 

TurboBasicXLv1.5 - BGP Viewer.atr

[Rybags]

Yep, I've done the same. Easy method is to just have a DList which you change with 1 less blank line each 2nd field.

 

NTSC you won't get the benefits, you really need a real TV or monitor to see actual results, emulation often looks better than reality with these modes.

 

Also I find the blank lines can be made less noticable by using Luma 2 on the coloured lines rather than Luma 0.

[flashjazzcat]

Looks bloody good in Altirra with frame blending turned on, but will have to test it on real hardware tomorrow. Looking forward to it.

[+Stephen]

I tested this on my PAL 130XE. It is using an s-vid connection to a scan doubler, which goes into an LCD VGA monitor. I get the same blank line issue as regular APAC mode on this setup. I will try testing this with an NTSC machine on my 1084S monitor sometime. Unfortunately, my 1084S cannot do PAL in colour.

[Heaven/TQA]

yeah... and don't forget even in emulator environment... switch to fullscreen and not watching it in small window... as obviously this fools your eye, too... as your pixels are less blocky

[bugbiter]

I've got a small 10" PAL/NTSC multimode CRT monitor which makes the 80 horizontal pixels look very nice and small :-) In any case its good to stand back from the monitor a bit with gtia modes...

 

I was really surprised to see NTSC in full colour here! It works! But maybe only on a 1200xl as it has the notoriously high colour saturation anyway? (good thing: 60hz nearly makes it flicker-free:-)

 

@ Rybags: just turning one blank line in and out wouldnt give me 240 resolution, just duplicating the 120. I ve got luma and chroma here 240 lines each! :-)

Thanks for the luma 2 hint, I will try it!

[flashjazzcat]

Looks good on a PAL1200XL with 1084S, Y/C input:

 

 

Great work on the viewer, bugbiter!

Edited September 24, 2013 by flashjazzcat

[Rybags]

There's not much point putting a luma line as the first scanline as a proper display will show it unblended, ie shades of white.

So, the first line can be the blank that appears each 2nd field.

 

Overcoming scanline 240 bug is a little tricky - you can display hires/GTIA on scanline 240 but need to turn off lower 2 bits of DMACTL just after the display finishes. Then you need to leave them off (ie have SDMCTL also with them off) until the normal display starts again.

A DLI on the first scanline can suffice but then you lose that line. Alternate to that is either use a delay loop (WSYNC and/or VCOUNT) or a Pokey Timer.

At the top of display you then need to set DMACTL lower bits back to whatever screen width you're using.

 

I think you can get away with using DMACTL Wide mode as alternative to turning the display off in blank/VBlank area but you then need to set back to normal mode at start of Antic's display. In this case you'd probably also want to set PF1/PF2 to same colour as COLBAK, or if desired to whatever border colour you want shown.

[flashjazzcat]

I wonder if we could get 25fps 480i video using a modified version of Avery's SIDE player?

[Rybags]

I tried static 480i stuff with APAC and TIP from memory.

 

There's not really an improvement, probably because essentially we're throwing away half the resolution vertically in those modes anyway.

 

So the end result is that we get the mainly visible scanlines appearing adjacently and looking slightly thicker than normal with some flicker.

 

I think the real strength with a 480i video mode would be with RasterConverta images, the doubled vertical resolution would be usable and noticable.

[+Stephen]

Looks good on a PAL1200XL with 1084S, Y/C input:

 

20130924_121002.jpg

 

Great work on the viewer, bugbiter!

Damn - I wish a had a proper PAL CRT now! I will see how my NTSC machines display this on the 1084 this evening. I will test with a 130XE as well as an 800.

[flashjazzcat]

Most pleasing non-VBXE-assisted colour images I can recall seeing on the A8 in a long while.

[bugbiter]

Damn - I wish a had a proper PAL CRT now! I will see how my NTSC machines display this on the 1084 this evening. I will test with a 130XE as well as an 800.

Don't worry - it'll look fine on NTSC. The image will be a little taller though..

Most important is that your machine has a decent GTIA chip. I've seen HUGE differences there.

Most GTIAs show those nasty dark gaps between certain Gr.9 luminances which cause the pictures to have ugly 'shadow areas' (And I don't mean the faulty chinese ones)

I have 13 Atari machines in my basement collection but only 2 of them have a really clean GTIA Gr.9 image without any gaps.

[bugbiter]

Most pleasing non-VBXE-assisted colour images I can recall seeing on the A8 in a long while.

Thanks a lot. I'll post more pics and I'll also give you my Turbo Basic converter.. :-)

[Irgendwer]

What do you guys think about it?

 

There was a special Atari edition of the german computer magazin 'Happy Computer' ('2. Atari XL/XE Sonderheft'), where this 'mode' was utilized for a painting program as well as a fractal (Mandelbrot) calculation program in Turbo-Basic. If there is really demand, I could try to find disks and upload both of them here.

 

I don't have test your images on a real machine yet, but AFAIR this mode is likely to produce headaches - at least with 50Hz PAL.

Edited September 24, 2013 by Irgendwer

[flashjazzcat]

If there is really demand, I could try to find disks and upload both of them here.

 

 

 

I'd certainly like to look at them.

[bugbiter]

There was a special Atari edition of the german computer magazin 'Happy Computer' ('2. Atari XL/XE Sonderheft'), where this 'mode' was utilized for a painting program as well as a fractal (Mandelbrot) calculation program in Turbo-Basic. If there is really demand, I could try to find disks and upload both of them here.

 

I don't have test your images on a real machine yet, but AFAIR this mode is likely to produce headaches - at least with 50Hz PAL.

I remember that Issue! I think it was a type-in program, right? I have lost the disk with that program though.

Thats exactly the mode Im talking about. Do you know if the programs are available somewhere?

Didn't have diditized images then-I think I doodled around with the painter a while but didn't amount to very much. It was running awfully slow as I recall...

[flashjazzcat]

That photo of the bearded guy cropped up elsewhere as a standard resolution APAC image.

[bugbiter]

Here are some more:

 

 

And I just love that one almost 3D...

 

 

if you want to load from D2: or H: , just change H$ in line 180.

[bugbiter]

..and here are the files:

BGP-PICS1.rar

[flashjazzcat]

Recognizable jubblies on a stock A8: never thought I would see the day. Easy to see what drives innovation.

 

Thanks!

[+CharlieChaplin]

Well,

 

the program is called "Paint 256" and has standard 80x96 pixels resolution (62 sectors, 7680 bytes in length). It is fully compatible to (or maybe also known under the name) Apac-2. The first part/half of the pic is Gr. 9, the second part/half of the pic is Gr. 11 (or vice versa). The computer mixes the half-pictures into a fullscreen 80x96 pixels graphic with no flicker, therefore you have only a low resolution. http://www.atarionline.pl/v01/index.php?ct=utils&sub=2.+Grafika&tg=Paint+256#Paint_256

 

There are flicker-programs like Escal-Paint, Digi-Paint, Pryzm, etc. that use 80x192 pixels resolution (123 sectors on disk) with interlace/interleave and there is Technicolour Dream that works without flicker and over/underscan but only 80x119 pixels resolution. http://atarionline.pl/forum/comments.php?DiscussionID=1159&page=1#Item_0

http://atarionline.pl/forum/comments.php?DiscussionID=746&page=1#Item_0

 

Looks like your mode uses both interlace/interleave and over/underscan. How about a PC program that converts GIF87a, JPG, PNG, BMP, TIF or other formats into your 256-colour, 80x239 pixel format ? And then a fully automatic slideshow-program for the A8 in ML please...

 

Attached some examples (Apac, Apac-2/Paint-256, Technicolour-Dream, Pryzm/Digi-Paint) here...

-Andreas Koch.

apac_pix.zip

ap2_Paint256_pix.zip

Tech_Dream_pix.zip

pryzm_pix.zip

Edited September 24, 2013 by CharlieChaplin

[bugbiter]

Thanks for the post, Charlie I'll check them out! So the flicker APAC Mode has not been named officially in all those years??

I'd love to have a fast converter for all the pc file formats. Too bad I don't know how to code C or Java or else what you need for that..

 

So- well, here's my Turbo-Basic solution for BMP to flicker APAC:

TurboBasicXLv1.5 - BGP Maker.atr

 

You need a windows .BMP File.

 

Take irfanView for example to..

 

- resize/resample it to 80x239 pixels

- flip it upside down (bmp is encoded last line first, normally)

- save it to H: uncompressed, byte order should be blue,green,red

 

In the converter, enter filename without .bmp extender

You can enter an optional description of the picture, Return will be registered as eol, backspace is working within one line.

START starts conversion.

During that, the border will show the converted colour of the current pixel.

The white missile is the 'progress bar' :-)one step to the right for each finished line.

 

USE AN EMULATOR AT FULL SPEED!

 

Default drive for source .bmp and output file is H: You can change that in line 360.

If you want to try without dithering, change dither to zero in line 660.

 

After conversion the hue and bri files on the H: drive can be deleted.

The .bgp file is the output picture!

 

enjoy!

[+Stephen]

Thanks for the post, Charlie I'll check them out! So the flicker APAC Mode has not been named officially in all those years??

I'd love to have a fast converter for all the pc file formats. Too bad I don't know how to code C or Java or else what you need for that..

enjoy!

I'll take a look at your convertor, and see if I can come up with a PC version.

[bugbiter]

Awesome!

 

well, youll probably need the source code for the colourmatch routine.

Ive still got the slow basic colourmatch routine somewhere as well..

 

The math is trivial. For each pixel you just compare all 256 palette entries from the laoo.act palette file to the original bmp rgb color.

The distance of these two colours in rgb colourspace is sqrt(delta_red^2+delta_green^2+delta_blue^2) the colour with the smallest distance to the original one is chosen. (as we are just looking for the smallest distance you can as well skip the square root and thus save time..)

Add floyd-steinberg dithering and youre done.

 

If youve got any questions, I'm here :-)