Port to Vapoursynth API 4

[cN3rd]

VapourSynth got a big API change in R55 which broke compatibility with many plugins.

Note that I almost didn't change any code in the plugin, apart from adding Plugin::Version. I still need to figure out how to get a number out of the release tag, but it shouldn't be too complicated.

Tested only under windows.

[msg7086]

Thanks for the PR.

I have no idea about vsAPI v4. Does it completely break compatibility? Like, what if I use new v4 plugins with v3 API VS? Is it possible to have one plugin interface working with both old and new APIs?

[DJATOM]

It's actually not backward compatible. Yet APIv3 plugins works with APIv4 host. Sometimes there's inefficient cache usage and maybe other drawbacks but in general it's not so critical. There's a post on doom9 from Myrsloik that describes stuff better:

[AkarinVS]

In reality though, for video plugins, there are almost no benefits for updating to APIv4.

Unless you try very hard to expose both APIv3 and APIv4 interfaces, migrating to APIv4 means losing support for all previous VS versions. On the other hand, APIv4 VS can use APIv3 filters just fine. Contrary to popular belief, there is no performance penalty for using APIv3 filters in APIv4 VS (even the source filters that make use of nfMakeLinear, there is no performance differences whatsoever because APIv4 VS contains a proper workaround.)

[msg7086]

In that case, I'm thinking maybe we can keep 2 branches together for now, where v3 being the main one, and when most of us are on v4 then we can switch over. What do you guys think?

[DJATOM]

I'm fine with that decision.