Early VCS SECAM version differences

[Rom Hunter]

You would make me a very happy person if you can get hold of some Activision VCS SECAM ROMs.

 

[alex_79]

Cosmic Ark :

the starfield glitch doesn't appear here... It definitively fuel the explanation that on SECAM units, the colors aren't made from the TIA itself. By the way, the cart I have is the one that doesn't display the starfield if you disable color. It would be interesting to test with the second version that keep the starfield even with the color switch off.

 

There are two revisions of Cosmic Ark. One of them has the starfield effect switchable using the "TV TYPE" switch on the console.

That switch (along with left and right difficulty, select and reset) is just an input that can be read by the software, so it can be used for whatever function the programmer wants. SECAM consoles are different, because the line which should connect to the switch is hardwired to ground so, in the software point of view, the switch is always in the B&W position. The actual switch on the console is wired to the video circuit and switches the output from color to black&white in hardware.

 

Secret Quest :

Looks pretty bland, but playable, no odd colors to burn your eyes.

But you can't switch to the map/weapon selection screen for the same reason (thiS game needs a working TV TYPE switch)

 

 

I have a PAL 2600 Jr and an Atari 7800 that plays the games with their PAL colors, so I can tell that every game I have got the "right" palette, so none of these games have been modded for SECAM unit specifically. You can only assume that for Obelix, the programmers succeeded in chooseing colors that will fit both PAL and SECAM systems.

Yes, some PAL games published in the early '80s were programmed to display good colors even on SECAM consoles. Other titles that come to mind are Mario Bros, Pole Position and Asteroids. The downside effect was that color shades were lost in NTSC to PAL conversions because they would have looked bad on SECAM. For example, in the NTSC version, the road edge in Pole Position gets darker in the distance to improve the prospective effect and the ships on Asteroids use brighter colors than the score to compensate for the flicker. This was most evident on games that used a lot of color shades like Battlezone or PItfall 2: the PAL conversions of these games look really 'flat' compared to their NTSC counterparts.

Edited June 8, 2013 by alex_79

[CatPix]

There are two revisions of Cosmic Ark. One of them has the starfield effect switchable using the "TV TYPE" switch on the console.

That switch (along with left and right difficulty, select and reset) is just an input that can be read by the software, so it can be used for whatever function the programmer wants. SECAM consoles are different, because the line which should connect to the switch is hardwired to ground so, in the software point of view, the switch is always in the B&W position. The actual switch on the console is wired to the video circuit and switches the output from color to black&white in hardware.

 

 

But you can't switch to the map/weapon selection screen for the same reason (thiS game needs a working TV TYPE switch)

Thats for the info.

Tho, the color switch is working on the SECAM systems, because, on all games, moving the stwich effectively changes the display from color to monochrome.

I guess that in both cases, it keep the software on B&W, this make sense.

 

Thanks for the infos regarding the map. Most games I have are loose carts, so even on my PAL console, I never popped the map on. In fact, on my PAL unit, switching the color switch did nothing, so I though because it's a SCART model, the B&W mode was desactivated.

I'll try that when I'll get back at home

[alex_79]

The TV TYPE switch is only used in the early games for its intended purpose. Some later games use it for some gameplay function but most of the time it's just left unused. So usually it doen't have any effect on a PAL or NTSC console.

The modification of the switch behaviour was a way to get compatibility with all PAL games released before the SECAM 2600. If a game was programed with two palettes for color and b/w, only with the b/w one (designed to only use the 8 different luma values) all of the object without fail would have been visible and clearly discernible by using the 8 colors of SECAM palette. For example in the game Basketball the players have different colors but the same luma value when the TV TYPE switch is in COLOR position, therefore they both would have the same color on a SECAM 2600 without the TV TYPE switch pin hardwired to B&W and the game would have been unplayable.

 

 

P.S. If anyone have an extra SECAM 2600 please check this post in the marketplace. Thanks!

[+SpiceWare]

OK, here is a screenshot of your program running on a SECAM VCS. As expected it's a bit different from the emulator screenshot.

 

Interesting - could you give Timmy a try on your SECAM system? I came up with an on-the-fly color conversion routine that lets the player select NTSC, PAL or SECAM for their TV Type.

[SeaGtGruff]

Interesting - could you give Timmy a try on your SECAM system? I came up with an on-the-fly color conversion routine that lets the player select NTSC, PAL or SECAM for their TV Type.

I think you should be able to add some color changes to your sprites in Timmy to get the luminance change effect in SECAM. The grid I drew has color A for the odd lines and color B for the even lines, where color A is the same for a particular row and color B is the same for a particular column. So if you look at the grid and see a particular shade you like, it's fairly easy to figure out which colors to combine. For example, black alternating with magenta makes a lighter red, and flipping them around (magenta alternating with black) makes a lighter blue. If you're trying for one and end up getting the other, just swap the order of the colors around. I drew 50 blanked lines after VSYNC before starting the active display, so using Stella's line-numbering method-- which counts line 0 as the line where VSYNC is turned off-- the first active line in my grid is line 50 (an even line).

 

For convenient reference, the color combinations appear to be as follows-- (E)ven colors listed first, then (O)dd colors. Since some combinations are essentially variations of a particular color, I'm calling them COLOR 1, COLOR 2, COLOR 3, etc., where lower numbers are the darker shades and the luminance increases as the number increases. Some of the shades are difficult to tell apart, so I'm not sure if I've got the relative order of shades correct-- and some of the names I'm using are debatable (such as Light Green, should it be Light Cyan?):

 

Black (E) + Black (O) = Dark Gray 1 (solid Black)

Black (E) + Blue (O) = Dark Gray 2

Red (E) + Black (O) = Dark Gray 3

Red (E) + Blue (O) = Dark Gray 4

 

Black (E) + Yellow (O) = Gray 1

Black (E) + White (O) = Gray 2

Red (E) + Yellow (O) = Gray 3

Red (E) + White (O) = Gray 4

 

White (E) + Black (O) = Light Gray 1 (same as Gray 2?)

White (E) + Blue (O) = Light Gray 2

White (E) + Yellow (O) = Light Gray 3

White (E) + White (O) = Light Gray 4 (solid White)

 

Blue (E) + Black (O) = Blue 1

Blue (E) + Blue (O) = Blue 2 (solid Blue)

Magenta (E) + Black (O) = Blue 3

Magenta (E) + Blue (O) = Blue 4

 

Cyan (E) + Black (O) = Light Blue 1

Cyan (E) + Blue (O) = Light Blue 2

Blue (E) + Yellow (O) = Light Blue 3

Blue (E) + White (O) = Light Blue 4

Magenta (E) + Yellow (O) = Light Blue 5

Magenta (E) + White (O) = Light Blue 6

Cyan (E) + Yellow (O) = Light Blue 7

Cyan (E) + White (O) = Light Blue 8

 

Black (E) + Red (O) = Red 1

Red (E) + Red (O) = Red 2 (solid Red)

Black (E) + Magenta (O) = Red 3

Red (E) + Magenta (O) = Red 4

 

White (E) + Red (O) = Pink 1

White (E) + Magenta (O) = Pink 2

 

Blue (E) + Red (O) = Magenta 1

Blue (E) + Magenta (O) = Magenta 2

Magenta (E) + Red (O) = Magenta 3

Magenta (E) + Magenta (O) = Magenta 4 (solid Magenta)

Cyan (E) + Red (O) = Magenta 5

Cyan (E) + Magenta (O) = Magenta 6

 

Black (E) + Green (O) = Dark Green 1

Red (E) + Green (O) = Dark Green 2

Black (E) + Cyan (O) = Dark Green 3

Red (E) + Cyan (O) = Dark Green 3

 

Green (E) + Green (O) = Bright Green 1 (solid Green)

Yellow (E) + Green (O) = Bright Green 2

Green (E) + Cyan (O) = Bright Green 3

Yellow (E) + Cyan (O) = Bright Green 4

 

White (E) + Green (O) = Light Green 1

White (E) + Cyan (O) = Light Green 2

 

Blue (E) + Green (O) = Cyan 1

Blue (E) + Cyan (O) = Cyan 2

Magenta (E) + Green (O) = Cyan 3

Magenta (E) + Cyan (O) = Cyan 4

Cyan (E) + Green (O) = Cyan 5

Cyan (E) + Cyan (O) = Cyan 6 (solid Cyan)

 

Green (E) + Black (O) = Dark Yellow 1

Green (E) + Blue (O) = Dark Yellow 2

 

Yellow (E) + Black (O) = Yellow 1

Yellow (E) + Blue (O) = Yellow 2

Green (E) + Yellow (O) = Yellow 3

Green (E) + White (O) = Yellow 4

Yellow (E) + Yellow (O) = Yellow 5 (solid Yellow)

Yellow (E) + White (O) = Yellow 6

 

Green (E) + Red (O) = Orange 1 (use for Brown)

Green (E) + Magenta (O) = Orange 2

Yellow (E) + Red (O) = Orange 3

Yellow (E) + Magenta (O) = Orange 4

 

Some of these combinations don't appear to make much sense at a glance, but do in light of how SECAM works. For example:

 

Magenta (E) + Yellow (O) = Light Blue 5

 

The (E)ven lines use the Luminance and Blue signals from Magenta with the Red signal from Yellow.

The (O)dd lines use the Luminance and Red signals from Yellow with the Blue signal from Magenta.

(I think.)