It is generally recommended to mux raw streams (
.h265, etc.) into containers (such as using
MKVToolNix) before loading with source filters.
There are a few source filters that can be used to load videos into VapourSynth. If you have an NVIDIA GPU,
DGDecNV is recommended:
src = core.dgdecodenv.DGSource("src.dgi")
.dgi index file is generated for the source video file using the
DGIndexNV program in the package.
If you don't have an NVIDIA GPU,
L-SMASH-Works is recommended:
src = core.lsmas.LWLibavSource("src.mkv")
ffms2 can also be be used, although certain versions add extra black frames to the beginning of video:
src = core.ffms2.Source("src.mkv")