d2vsource: Use getPluginById

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
d2vsource: Insert cache filter between decode and RFF filters

Goes from 80 fps -> 1200 fps.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
d2vsource: Make RFF a boolean value

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
d2vsource: Cosmetics

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
ApplyRFF: Request frames in order

Out of order frame requests can be slow if they are outside
of VapourSynth's cached set of frames.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
d2vsource: Ask for a sample if we get a NULL frame

The cache currently hies this evil bug, so we need more
sources to help debug it. This is obviously a horrible
hack.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>