Screenshot turns out black

[mhluska]

I was getting completely black screenshots for certain videos and i think the reason comes down to either:

• The first frame of the video is black (dependent on video format possibly?)
• The video has a fade from black effect at the start

Would it make more sense to set the default seek_time for screenshots to something like 5 seconds? That way it "just works" for the majority of the users. I imagine most users won't care if their default screenshot is not at 0 seconds.