Fmtconv is a format-conversion plug-in for the Vapoursynth and
Avisynth+ video processing engines.

It does:
* Resizing.
* Bitdepth conversion with dithering.
* Colorspace conversion (matrix, transfer characteristics and
  chromatic adaptation).

It supports:
* Pixel data types: 8--12-, 14- and 16-bit integer, 32-bit float.
* Colorspaces: RGB, Y, YUV in 4:4:4, 4:2:2, 4:2:0, 4:1:1 and YCgCo
  with the same chroma subsampling factors.
* Progressive and interlaced content.

Fmtconv is focussed primarily on quality and exactness rather than
execution speed.  This does not mean it is slow or unoptimized, but
fmtconv is clearly not on par with the fastest equivalent 8-bit
filters.