Im trying to superimose qt.movie containig alpha channel over video input. Part of this alpha channel is semitransparent:
Each time, checking different codecs I receive blackish ugly outline around mask, and part with semitransparen alpha has black dominant: in video editing software are 2 types of alpha mixing - subtractive, and additive. Alpha can be premultiplied with black, and using aditive one can remove this black component when layering. How I can get rid of this unwanted outline, maintaining semitransparent part?