Atari 2600 definitive resolution?

[Chiptune Goon]

***Sorry if this is in the wrong section, but I thought that this question could best be answered by the people who visit this section of the forums.***

 

Yo, I'm a big fan of Atari 2600 games, I'm working on creating a game that graphically gives the impression of an old Atari game, but I can't seem to get a definitive answer on the resolution of the system.

I mean, if ya google "Atari 2600 Resolution," everyone says the resolution is 160x192,

but when playing Combat in the Stella emulator, the game is displayed with a resolution of 320x210 (Took a screenshot, put it in Paint and counted the pixels with the pencil tool)

2 pixels at the top of the window are a black bar.

Is the black bar just caused by hardware limitations at the time?

It seems that every game has a black bar of unused space and varying heights. I'd prefer to know what the maximum theoretical resolution is if the space where the black bar is COULD be used.

 

Is 160x192 supposed to be the resolution of the playfield?

If I subtract the height of the HUD and Black Bar from the total height I get 191, giving me a resolution of 320x191 for the playfield and 320x17 for the HUD (320x19 with the black bar.)

BUT, I noticed that the sprites seem to exceed the width limit of 8px, as they are 16px wide in the attached image, so that means that the image was stretched to be twice its regular width.

So if I divide the width in half, I get a playfield resolution of 160x191, which is pretty damn close to the 160x192 resolution that everyone claims.

But then why don't people include the extra 17-19 pixels above the playfield where the HUD is displayed?

 

I've included an image with my notes in the attachments

or you can see it here

http://imgur.com/mDR78Y0

 

[towmater]

Isn't the 2600's video an analog output? There's no "resolution" as such, then, because it is all about timing and how many times the cpu is able to change the output on the fly?

[fujidude]

Isn't the 2600's video an analog output? There's no "resolution" as such, then, because it is all about timing and how many times the cpu is able to change the output on the fly?

Only DVI, HDMI, and DP are digital outputs. Even VGA is anloag output. Just sayin'.

[Nukey Shay]

SeaGtGruff's reply (#4) covers pretty much everything here:

http://atariage.com/forums/topic/169128-what-is-the-atari-2600-screen-resolution/

 

A couple of points:

The 2600 has no native display kernel, so a program must use it's own. What you mention as being "unused" is often doing something...syncing to the television signal for a stable picture and time taken by the non-display kernel parts of the program. So the vertical resolution is n/a...only a guideline of 262 total lines maximum for NTSC, 312 for PAL (Vertical blank + visible display).

Smaller black lines or bars visible on the left side in many games are HMOVE artifacts (HMOVE is used for sprite horizontal repositioning)...tho there are a few ways to avoid them being visible.

 

Combat uses playfield pixels to draw the scores (not sprites). Each digit bitmap is 3x5...register PF1 is updated twice each scanline for each player's 2-digit score, and then repeated before changing the bitmap - the differing colors are done by invoking "score mode" for the playfield...it borrowing the P0/P1 sprite colors for the left and right halves of the screen respectively. The blank area below the score is due to the processor time taken by the program setting up the gameplay area loop and it's variables.