zimg: add semi-planar repacker

This is for formats like nv12 (including p010, nv24, etc.). Might be
important for hardware decoding. Previously, this would have forced a
libswscale fallback.

The genericism makes this only slightly more complicated. The main
complication is due to the fact that mixing planar and packed stuff is
insane (thanks, Nvidia).

P010 output will actually happily set any of the 6 bit "padding" LSB,
that are normally supposed to be 0 (for unpadded data there is P016).
Scaling happens with 16 bit precision. Not going to bother adding an
extra packer which zeros them out, or with shifting them in
packing/unpacking. Lets just hope nobody notices.

0 files changed, 0 insertions, 0 deletions