**System Information**
WIn10 GTX980Ti
**Blender Version**
2.79bd8ac9
**Short description of error**
When OpenGL render, alpha processing when saving with FFmpeg differs between 2.78 and 2.79.
It is not Unpremultiply 2.79.
**Exact steps for others to reproduce the error**
Add Background images > Draw Front > Opacity to lower > OpenGL render Animation(FFmpeg Video) save
{F948478}