Rewind problem

[rlbond]

When rewinding multiple times, rewind "skips" some of its previous states.

It's best shown with a game with a timer such as super bomberman.
Set the rewind timer to something nice (I set it to 25/5 = 5 seconds).

Now, start a multiplayer game in super bomberman. The timer will start at 2 minutes. At 1:50, press rewind. Predictably, the game will go back to the previous state (it was 1:52 for me). This means there are rewind save states at the following in-game times:

1:57
1:52
1:47, etc

so now wait until the time is 1:45, and press rewind twice. The first time it will back up to the previous state (1:47), but the second time it will skip the 1:52 state and jump straight to 1:57. I hope that makes sense.

[grinvader]

It makes sense. I have already talked about that with Nach, because I don't find it satisfying.

This is the cause:
When a rewind state is saved, it sets a timer to the value chosen by the user. Once this timer reaches 0, another rewind state is saved.
When you press the key, it loads the last state and erases it without regard to anything else, then sets the timer to the current value - so after the time is spent again, it saves a state.

Little picture in case I wasn't clear enough:
t = 0s | Save 1
t = 5s | Save 2
t = 10s| Save 3
t = 12s| Load 3 - State 3 erased
t = 15s| Save 3
t = 20s| Save 4

So when you reload them successively, the 't = 10s' state effectively disappeared and you jump from 15 to 5.

I can fix that behaviour in a snap, but then you wouldn't be able to go 2 rewinds back (which means, baaad fix) because you'll reload the last one forever.
To fix it and keep prev-prev rewind load feature functionnal, we could mimic the code used for chapters in movies. This would require a bit of work to rewrite the rewind routines, of course.

[Noxious Ninja]

Couldn't you use a linked list for the rewind states? Or am I completely misunderstanding the problem?

[rlbond]

yes, or perhaps do some sort of "if it's been x seconds since I've made a rewind state, go back 1 state and erase that 1; if not, go back 2 and erase 2" kind of thing. Of course I have no asm experience so I don't know how hard this would be.

[Nach]

Couldn't you use a linked list for the rewind states? Or am I completely misunderstanding the problem?

The latter.

Of course I have no asm experience so I don't know how hard this would be.

Main rewind code is in C.

[grinvader]

Main rewind code is in C.

^_^ the second thing I worked on, and the first as official ZSNES dev.

[rlbond]

well then, it probably wouldn't be too hard, compared to a lot of other stuff.