08287: a2600: Frames are being blended together

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
08287	Graphics	Major	Always	Apr 7, 2022, 03:44	Sep 23, 2022, 23:25

Tester	Yonah	View Status	Public	Platform	MAME (Official Binary)
Assigned To		Resolution	Open	OS	Windows 10/11 (64-bit)
Status [?]	Acknowledged			Driver	atari/a2600.cpp
Version	0.242	Fixed in Version		Build	64-bit
		Fixed in Git Commit		Github Pull Request #

Summary	08287: a2600: Frames are being blended together
Description	Every frame appears to be blended with the previous frame, similar to the effect of using motion blur. HLSL is not enabled. See included animation taken from E.T.
Steps To Reproduce	Use SHIFT+P to observe frame by frame.
Additional Information
Github Commit

Flags
Regression Version
Affected Sets / Systems	a2600

Attached Files	a2600-Frames.gif (38,221 bytes) Apr 7, 2022, 03:44 Uploaded by Yonah

No.20018 CYBERYOGI -CO-Windler Viewer Apr 7, 2022, 07:38 edited on: Apr 7, 2022, 07:41	A VCS2600 is intrinsically flickery. Some games have sprites flashing up only every 2nd or 3rd frame (often varying by visible sprite count on screen), other use homemade interlace tricks (drawing sprites every 2nd scanline either alternatingly or omitting always even or odd scanlines) etc. Not even the framerates are stable because it has no framebuffer and everything is very software-defined (bitbanging/cycle counting without IRQ), so screen output is almost as flexible as a vector display. I.e. playing at reduced framerate (showing only every 2nd or 3rd frame) may make certain sprites sporadically invisible, which would disturb gameplay very much. Also digitizing the stuff for youtube often makes such trouble. Therefore the blur was likely added to mitigate such nuisance, but it definitely needs an option to turn it off.
No.20034 ICEknight Tester Apr 7, 2022, 18:17	Shouldn't this stuff be handled by the shaders? Or did the original hardware not display any of that flickering?
No.20063 Tafoid Administrator Apr 15, 2022, 18:45	I'm pretty sure it was implemented to be this way always. Should it be changed or can it be easily adjusted? Hard to say. I'll acknowledge for now.
No.20562 ICEknight Tester Sep 23, 2022, 18:43	Just wanted to point out that this also happens in 2600p (its PAL clone) and in 2600_pop (which is not listed as a clone). I couldn't find any other driver that does this additional blur, which is now redundant with the phosphor decay options in the current shaders (and collides with them since it can't be turned off).
No.20563 Haze Senior Tester Sep 23, 2022, 23:25	The Game Gear driver does similar, but yeah, it should really just be post-process at this point.