Remove duplicated out-of-loop init code, and do color matrix
initialization at the beginning of each y iteration.
Allow factorization and avoid an useless matrix update in the last
iteration.
The previous table appears to be wrong (it was copied from the original
MPlayer super2xsai filter in order to keep binary compatibility).
The new table is consistent with the init code and apparently fixes a
combing artifact on the left edge of the generated image.
Partially based on the port by Niel van der Westhuizen
<nielkie@gmail.com>, done for GCI 2010. Same output as the original
filter and as fast.
See thread:
Subject: [FFmpeg-devel] [PATCH] Port MPlayer 2xSaI filter to libavfilter
Date: Thu, 25 Nov 2010 01:31:24 +1000
Stefano Sabatini
Paul B Mahol