When scaling down by 2 the formula should round consistently.
(a+b+c+d+2)/4
The C version did but the SSE2 version was doing 2 averages.
avg(avg(a,b),avg(c,d))
This change uses a sum, then rounds.
R=dhrosa@google.com, harryjin@google.com
BUG=libyuv:447,libyuv:527
Review URL: https://codereview.chromium.org/1513183004 .
Low level for NV21ToARGB written to accept yuv matrix used by
other YUV to ARGB functions.
Previously NV21 was implemented for Windows using NV12 with a different
matrix that swapped U and V. But the Arm version of the low level does
not allow the matrix U and V contributions to be swapped.
Using a new low level function that reads NV21 and uses the same
yuvconstants as other YUV conversion functions allows an Arm port of
this function.
TBR=harryjin@google.com
BUG=libyuv:500
Review URL: https://codereview.chromium.org/1388273002 .
