Device Check

※ For filter developers

Device check ensures valid device combinations when generating clip instances. Throws error if invalid.

In core Avisynth

Core Avisynth calls SetCacheHints to obtain supported devices and checks combinations.

Clip device priority:

1. CACHE_GET_DEV_TYPE result
2. DEV_TYPE_CPU

Required child device priority:

1. CACHE_GET_CHILD_DEV_TYPE result
2. CACHE_GET_DEV_TYPE result
3. DEV_TYPE_CPU

Pseudocode:

devs = required devices for clip A
foreach(B in child clips of A) {
    child_devs = B's devices
    if((devs & child_devs) == 0) throw
}

Return DEV_TYPE_ANY in CACHE_GET_CHILD_DEV_TYPE to disable core check.

Filters supporting multiple devices must intersect child devices, else error.