[PS Vita] Castlevania Aria Sorrow slowdown

[Erken22]

Castlevania aria sorrow slows down with sound lags at the beginning of the game, when it wakes up and a special blur effect appears on the screen, in early builds I don’t remember exactly which ones, like from August to October I didn’t play on the ps vita 2000. I don’t notice any slowdowns. I'm currently playing on the ps vita1000 fat model and I'm noticing slowdowns when the blurry squares effect appears at the beginning

[andymcca]

This will probably be the Mosaic effect which was implemented within the last year - not sure if it should be having that much of a performance impact, maybe if it needs a lot of RAM tho and cache flushing/swapping might be happening?

[Apaczer]

@andymcca I've also noticed big hit with mosaic effect, for e.g. Super Mario Advance after game creation (https://youtu.be/pbSWJCzmCNI?feature=shared&t=125) almost 15fps drop. This is of course for low-end Miyoo arm32 platform with 32MB of DDR1.

Any chance to optionize new video driver or mosaic effect? I believe most folks would vote for speed over accuracy if it goes for gpSP.

[Erken22]

It is interesting that the mosaic effect is also implemented in vba next, but there is no slowdown during the mosaic effects

[andymcca]

I have an idea for speeding up the current per-pixel implementation of the mosaic effect. Will try it out in the coming days and update here

@Apaczer I've almost certainly used up all my free time bonus for a while just with this weekend's activity here!!! So may be a while before I get to this, but having looked into it I think the reason for the slowdowns could be the liberal use of the Modulus operator (%) in the Mosaic code, and at a pixel-by-pixel level in some cases. This will likely be slow on some platforms such as older ARM especially as we're not dividing by a constant (the compiler would likely optimise this to a shift instead). So I'm looking at how to substitute these calls either with faster equivalent operations e.g. Bitwise and/or optimising the render functions in general (can probably loop repetitive pixels and maybe even cache object/bg rows if appropriate). When I make the changes and do a PR, I'll hit you up so you can test on your ARMv5 device if that's ok?

[davidgfnet]

We could indeed speed up a bit the mosaic effect, however its nature is quite slow. At the moment the video engine is pretty optimized, so mosaic effects break that faster code path.
We could add an option to disable mosaic effect or even to have some faster but less accurate mosaic mode (ie. mosaic by power of two or something similar).