Stella - Monitoring Scanlines and Flagging

[Christopher Tumber]

I'm using developer settings to show scanlines in real time, however it can be difficult to pay attention to both the information overlay and whatever is happening onscreen (ie; if interacting with game to test collision detection)

 

I'm also setting a breakpoint using breakIf _scan==#263 to flag if the screen ever exceeds 262 scanlines but this won't trap cases where the screen is below 262 scanlines.

 

Is there a way to make it really obvious in Stella that there's been a scanline issue? Doesn't necessarily need to be a breakpoint (the problem likely occurred well before the bottom of the screen anyhow). Could be a flash or a pause in emulation. Just something to make it obvious.

 

I may be approaching this completely ass backwards so if anyone has strong methodology for testing picture stability that isn't "run it on a real TV and watch for roll"  please share.

 

 

 

 

 

 

 

 

Edited June 4, 2023 by Christopher Tumber

[JetSetIlly]

My emulator, Gopher2600, has a timeline window in the debugger. This shows the history of the scanline count over recent frames.

 

For example, when running your ROM I can see there was a scanline issue during the switch from the title screen to the play screen. The red line gives a general idea of what is happening to the scanline count each frame and the red triangle draws attention to it.

 

 

Hovering over the timeline gives numeric detail and thumbnail of the offending frame

 

 

I've played the game a little and I didn't encounter any other scanline issues.

 

 

edit: You can also set a breakpoint with BREAK JITTER that will halt execution whenever the scanline count changes.

 

Edited June 4, 2023 by JetSetIlly

[alex_79]

2 hours ago, Christopher Tumber said:

I'm also setting a breakpoint using breakIf _scan==#263 to flag if the screen ever exceeds 262 scanlines but this won't trap cases where the screen is below 262 scanlines.

breakif _scanEnd!=#262

 

_scanEnd is the scanline count at the end of the last frame.

 

[Christopher Tumber]

Thanks guys both these look super-helpful!