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256x192 seems too much limited for safe area. When I worked in game company where we made games for NTSC TV console, we had safe area 288x216 and text safe area (where text is surely readible) 272x202 in 320x240 resolution on 14''..21'' CRT TV's.

I think, I must check some games to get statistics, where important info usually displays.. I get idea that left/right screen edges must have big margin for important info, but I'm not sure about up/down edges.

Shiru wrote:256x192 seems too much limited for safe area. When I worked in game company where we made games for NTSC TV console, we had safe area 288x216 and text safe area (where text is surely readible) 272x202 in 320x240 resolution on 14''..21'' CRT TV's.

I think, I must check some games to get statistics, where important info usually displays.. I get idea that left/right screen edges must have big margin for important info, but I'm not sure about up/down edges.

The two safety zones tend to be defined this way: The first is where it's safe for game play (action), and that is 90%. 90% of 320x224 is 288x202. The second safety zone is for titles - things the user MUST be able to read under any circumstances, and that is 80%. 80% of 320x224 is 256x180.

Sounds like your company was a little less strict on the second zone.

Chilly Willy wrote:Sounds like your company was a little less strict on the second zone.

They developed their standarts in 2000s, maybe safe area on modern CRT TV's bigger than on 1990s TV's.

I did quick check for safe area in different SMD games, and now it's clearly looks like most of games assumes that text safe area is 288x208 - important information like life bars and game statistics (with graphics or text) always locates in this rectangle. Sometimes this area is smaller, seems like that more usual for older games.

Shiru wrote:256x192 seems too much limited for safe area. When I worked in game company where we made games for NTSC TV console, we had safe area 288x216 and text safe area (where text is surely readible) 272x202 in 320x240 resolution on 14''..21'' CRT TV's.

I think, I must check some games to get statistics, where important info usually displays.. I get idea that left/right screen edges must have big margin for important info, but I'm not sure about up/down edges.

288x216 is the action safe area given in the image.

There are two values given for title and action safe. One is 80% and 90% of the screen. The other is 90% and 95%. I'm not sure which is correct.

The PAL image uses the 80% and 90% values.

For PAL there is no need to worry about the up/down sides of the screen, overscan will always be there.

Before you find out the safe area of 40 cell mode, you need to figure out the dot clock for the horizontal line. 320 pixels isn't edge to edge.

If I remember correctly, the mast clock for the NTSC Genesis is 53.7mhz.

40 cell mode should be 53.7mhz/8 = 6.7125mhz / 15735 hz = 426 pixels per scanline / 1.186 ( hblank/front porch/color burst subcarrier/etc) = ~360 displayable pixels. Only 320 pixels are used, the rest are clipped.

So if you're going to figure out safe area, then use the displayable pixel number- 360 not 320. Of course I'm assuming 320 pixel area of the scanline is perfectly centered in the 360 pixel total width, otherwise factor that in.

On every modern standard overscanned TV I've hooked up my Genesis to, the entire addressable screen is visible with maybe a tiny sliver of vertical border at the bottom, and the VDP RAM garbage in the bottom border is NOT visible. Here is an old vidcap screenshot I took of my Genesis:



This is taken based on a standard 4:3 DV NTSC resolution of 720x480, cropped to 704x480 (which is the true 4:3 NTSC resolution when concerning digitized video, the extra 16 pixels are merely meant to account for slight timing errors that would shift the video to the left or right). As you can see, I did not crop into the Genesis' display itself, as you can see the border drop off to black right before the edge of the image.

Maybe on some older sets, oxygen leakage into the tube could cause some zooming on the image, but I think for most TVs a 5% solid safe area would be sufficient (and might still be slightly overkill). If you're overtly paranoid about your data not being seen on really old TVs then I'd go no higher than 10% safe area. But based on my experience, I don't really see that we would need to differentiate between action safe and title safe.

Action and text safe area differs by how clear picture visible is. Edge parts of TV screen can be less focused (so text will be hard to read), and for old TV's they not make real rectangle, they make smoothed rect.

this is my capture..

Just for information, which height/width is the overscan area on each side ?

Up down, 8 pixels, left right 14...16pixels

thanks !
and what about borders in PAL 224/240 mode ?
Is there a relation between those borders height and classical TV resolution height (240 in NTSC, 288 in PAL)

For example, in NTSC: (240 - 224) / 2 = 8 lines border on each side

if we apply the same formula for PAL genesis, ie:
(288 - 224) / 2 = 32 lines border on each side in 224 mode
(288 - 240) / 2 = 24 lines border on each side in 240 mode

I owned a PAL genesis but don't remember that there were so many border lines so maybe I'm wrong somewhere ?

My TV shows about 32pixels of overscan on upper and lower side in 224/448, and 24pixels in 240/480. Other TVs I've seen show around 16pixels of it (and less when in 240).

Thanks a lot
I guess this will help me emulating those borders properly: actually on the Gamecube, any 320(or 256) x 224(or 240) genesis display is scaled by the GC hardware to 640*480, without differencing PAL & NTSC, which is not completely accurate in term or ratio I imagine

If it matters, this is what my TV shows (CRT).

the genny is in NTSC mode (connected via RGB).





and here it is with PAL mode (RGB).