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question about "jumping " screen


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#1 easmith OFFLINE  

easmith

    Chopper Commander

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  • Location:Alexandria, VA

Posted Mon Jul 23, 2018 1:32 PM

It is not very apparent in stella, but when I play my game ( below) on Harmony with real 2600, the screen is very stable, but "jumps " fairly severely just at the exact moment when a wave is cleared,  and then restabilizes.   

 

Any ideas on what could cause this or any hints on how to figure it out?

 

 

ES

 

Attached Files


Edited by easmith, Mon Jul 23, 2018 8:38 PM.


#2 stephena OFFLINE  

stephena

    River Patroller

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Posted Mon Jul 23, 2018 3:06 PM

No idea what is causing this, but it might also become more apparent if you turn on jitter/roll effect in the TV settings.  Once you see it in Stella, maybe you can note the scanline count, etc and narrow it down from there.



#3 SpiceWare OFFLINE  

SpiceWare

    Draconian

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Posted Mon Jul 23, 2018 3:58 PM

Toggle your Frame Stats - ALT-L or CMD-L per the Developer Keys section of Stella's help.

 

Screen Shot 2018-07-23 at 4.49.30 PM.png

 

The 272 is how many scanlines your game is using.

  • 272 is too many scanlines for NTSC, should be 262
  • 272 is too few scanlines for PAL, should be 312

 

Some TVs will be OK with the extra 10 scanlines, others won't be.

 

Hold down RESET and the scanline count will jump to 283.  Even if your TV can show it, the difference of 11 will cause the screen to jump.  I don't know about your Wave Clear, as I don't know how to play this game, but suspect its also going to 283 scanlines.

screenshot2.png



#4 easmith OFFLINE  

easmith

    Chopper Commander

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Posted Mon Jul 23, 2018 4:55 PM

Thanks.  I know I'm a bit over the scanline count but 272 seems to be ok for my TV  .      I don't understand how  waveclear would affect the number of scanlines, since the kernel is unaffected..   And I am ok with a jump at reset.

 

Could it be that the logic that is performed after the waveclear is taking too many cycles?  I even edited the code to jump straight from the wavweclear logic to the next frame bypassing the normal logic . 

 

Play is pretty simple just fire with joystick and shield with button , start with button.

 

The number of enemies is RAM E1   . The number of enemies killed is RAM E2.  If you make RAM E2 equal  RAM E1 and then  hit Frame +1, the scanlines jump to 292  , Total CLKs  changes drastically, next frame is 178. then back to 272.    Hmmmmmmm


Edited by easmith, Mon Jul 23, 2018 5:37 PM.


#5 easmith OFFLINE  

easmith

    Chopper Commander

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  • Location:Alexandria, VA

Posted Tue Jul 24, 2018 7:07 AM

I fixed the jumping at the wave clear thanks for the help




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