This fix addresses some problems with very complex clips like
handling of flashes on clips like crew (which was made worse
by an earlier patch (derf and std-hd)).

Most clips a small effect but some between 1 & 2%

Derf +0.039, +0.211%
YT +0.042, +0.083%

Change-Id: I65fc7c13afc31482040068544dd65b8808f5cb4a