Replay desync

[RNG]

What's the cause of all the annoying replay desync from Touhou 10 on? It seems to plague my replays quite a bit - my TD replays, especially, tend to screw up around stage 4 or 5 - and I'd like to know if this has to do with having a shitty computer or if there's anything I can do to fix it.

[Agent of the BSoD]

Replay desyncs are a known issue with most of the latter Touhou games. It sometimes helps to start the replay from the stage before the desync (like in the case of SA stage 6) but sometimes it's just going to be unavoidable. I've got a replay from PCB that desyncs on the Prismriver's fight, which is the only time I've seen that game ever desync a replay. There isn't really much else you can do if a replay desyncs, as it's an issue with the games.

[Karisa]

MoF stage 4 near the start can generally be prevented by starting from stage 3 (fast-forwarding is fine).
SA stage 6 Utsuho's first nonspell can generally be prevented by starting from the beginning (stage 5 may work, but if it doesn't, stage 4 probably won't work either but beginning should work, in my experience)... annoying, yes, but at least it's watchable.
PCB desync, if it occurs, will not be preventable as far as I know. At least it's much rarer than those two. It happened to me once, but this is the second time I've ever heard of it occurring.
It's never occurred in any other games for me.

Sometimes I wonder if in MoF+ it relates to potential variance in stage loading time, that might be prevented by always remaining still during stage transitions. Just a theory without any evidence though (just like the theory that not shooting when Shinki appears prevents the random death glitch, which turned out to be untrue).

[Agent of the BSoD]

MoF stage 4 near the start can generally be prevented by starting from stage 3 (fast-forwarding is fine).
SA stage 6 Utsuho's first nonspell can generally be prevented by starting from the beginning (stage 5 may work, but if it doesn't, stage 4 probably won't work either but beginning should work, in my experience)... annoying, yes, but at least it's watchable.
PCB desync, if it occurs, will not be preventable as far as I know. At least it's much rarer than those two. It happened to me once, but this is the second time I've ever heard of it occurring.
It's never occurred in any other games for me.

Sometimes I wonder if in MoF+ it relates to potential variance in stage loading time, that might be prevented by always remaining still during stage transitions. Just a theory without any evidence though (just like the theory that not shooting when Shinki appears prevents the random death glitch, which turned out to be untrue).

Well the SA stage 6 desync happens only during Utsuho's nonspell, and the stage itself is unaffected. There's probably some timing error for when the conversation comes up, but it's odd that it only happens when you start the replay from stage 6. (stage 5 has always solved it for me)
IaMP has desyncs as well for story mode due to some random calculator or something. That one's unavoidable too.
I've never had MoF desync anything before, it's just been PCB, IaMP, and SA.

[Karisa]

For Utsuho's nonspell, I wonder if it relates to the RNG somehow. The stage portion is mostly aimed and static, while the nonspell seems randomly oriented. Anyway, I think the replay where none of stage 6, 5, and 4 worked but stage 1 did was UKT's previous record (the 4.74b one)... edit: wait, what? I just played that back from the start, fast-forwarding through the entire thing, and it desynced anyway? That's weird...

And I thought MoF 4 always desyncs sooner or later if you start a full-game replay from that stage?

[Zil]

Well if you fast forward at any point in a SA replay, it will desync at the nonspell, regardless of where you started.

As for RNG's original question, I know there was a patch for TD that fixed something about it desyncing whenever you tranced. Also something about the game crashing if you're trancing when Mamizou's survival spell ends. You've probably already got that though so I don't know.

[Agent of the BSoD]

Well if you fast forward at any point in a SA replay, it will desync at the nonspell, regardless of where you started.

Not for me. I can start at stage 5, fast forward the entire way up to Utsuho, and it plays just fine. (whereas the same replay would desync if started at stage 6) It's funny that most people say not to fast forward and I've never had a single issue with it.

[Zil]

Strange indeed. I wonder why it would vary from person to person like that. It does make it seem like it should be preventable or something. No idea how, of course.

And just to add to the list of offenders, I know I've seen a PoFV replay desync as well. Only once though.

[Karisa]

As for RNG's original question, I know there was a patch for TD that fixed something about it desyncing whenever you tranced. Also something about the game crashing if you're trancing when Mamizou's survival spell ends. You've probably already got that though so I don't know.

In the unpatched game it crashes if you're not bombing when Mamizou's survival spell ends. Something about too many animal bullets on screen, I think. It's impossible to capture in v1.00a, so if you've ever captured Mamizou's survival, then you already have the patch applied.

I don't remember a trance-induced desync, but I think the demo had a desync from using Youmu's bomb, since the random slashes of the bomb were still randomized in the replay.

Also I know v1.00a replays desync if played back in v1.00c.

I've never noticed a difference between fast-fowarding and not fast-forwarding affecting replay desync, either. At least, I fast-forward the BoWaP safespot in almost every SA ReimuA scorerun I watch, and the Utsuho desync never occurred when starting from stage 1 except in that specific UKT replay.

[Ranko Hoshino]

Also I know v1.00a replays desync if played back in v1.00c.

Jaimers's perfect TD Stage 6 replay from 1.00a strangely plays back correctly on 1.00c for me. My game doesn't even crash at the end. I just felt like mentioning this.

[Karisa]

OK, maybe it's just that some v1.00a replays desync in v1.00c. At least including my first Extra attempt, which I'd saved because I'd somehow captured all of Nue's spells on the first try.

And the stage practice replay crash seems to only be in stages 1-5 as far as I know.

[RNG]

The replay worked correctly when I played it from Stage 1 without fast-forward. Oddly, though, when I started it from any other stage the RNG was totally different - my inputs worked correctly, but for example when I started on Stage 3 Kogasa moved in the wrong direction after one wave of her spellcard.

I can only conclude that ZUN was drunk when programming replays from MoF on.