Quote:
Originally Posted by davidhorman
Can someone give me a dumbed-down summary of the different MT modes? I've read this:
http://avisynth.nl/index.php/AviSynt...orrect_MT_mode
But it's not very clear to me. It doesn't really state how the modes work, and especially the bit for MT_NICE_FILTER isn't clear at all on when it should be used, instead focusing on when it shouldn't.
I'm guessing that MT_NICE_FILTER requests multiple frames in multiple threads, but only one instance of the filter, and that MT_MULTI_INSTANCE makes multiple instances, so it's a bit like calling the same plugin multiple times on trimmed/selecteveryed subclips and then joining or interleaving them? Or does it crop frames up into smaller frames then stack them back together, or something? (probably not) And that MT_SERIALIZED is the same as plain old single-threaded AviSynth? |
I wrote
this a while ago. May or may not help.
The tl;dr is that as a rule of thumb:
- if your filter's GetFrame is threadsafe (basically, does not attempt to write to any memory that is not explicitly associated with this specific frame request) => MT_NICE_FILTER
- if your GetFrame does depend on shared state of some kind, but your filter supports things like interleave(yourfilter().selecteven(), yourfilter().selectodd()) in vanilla Avisynth => MT_MULTI_INSTANCE
- if you are a source filter, or rely on frame request order (i.e. stuff with side effects outside Avisynth such as writing to a file), or rely on internal state that changes with every frame request (i.e. pattern-tracking decimation filters) => MT_SERIALIZED
It also may or may not be relevant to note that all GetFrame calls that need to happen to produce a given output frame at the end of the script happen in the same single thread, regardless of what MT modes are in use. You probably shouldn't rely on this for anything, though.