Yes, because that doesn't actually work proper. In order to seek fast while having the ability to start encoding at any point without issues with keyframes, I need to actually do `ffmpeg -ss X1 -i FILE -ss X2 -t (Y-X)` where X1 + X2 = X.

Compare:

    frontend -s 05:28:38.667 -e 05:28:58.767 input.ts
    ffmpeg -ss 05:28:28.667 -i input.ts -ss 10 -t 20.100 -pass 1
    ffmpeg -y -ss 05:28:28.667 -i input.ts -ss 10 -t 20.100 -pass 2