First we shift the values up to the actual amount of bits in draw_ass,
so that they will be drawn correctly when using formats with more than
8 bpc. (draw_rgba is already correct w.r.t. RGB formats with 9 or more
bpc)
Then, in scale_sb_rgba, by setting the amount of bits per channel used
for planar RGB formats (formats are always planar at this point in
draw_bmp) to be the same as the source from 9 to 16 bpc (in effect all
the various GBRP formats) we manage to fit the special case that does
not require any conversion in chroma_up and chroma_down when handling
these formats (as long as the source itself is a planar format),
instead writing directly to the combined dst/src buffer. This in turn
works around a bug (incorrect colors) in libswscale when scaling
between GBRP formats with 9 or more bpc. Additionally this should be
more efficient, since we skip up- and down-conversion and temporary
buffers.
Anton Kindestam
d00f9b19c7