[JoshTriplett]

> After uploading, YT gives you 3-5 thumbnails you can choose from.

Can you pick an arbitrary video frame, or only one of the suggested thumbnails?

[nacs]

It automatically captures 3 different thumbnails (I guess using the algorithm in OP) and lets you select any 1 of those 3.

[lumpypua]

I presume they use the image selection as training data too—if not that seems like awfully low hanging data fruit.

[chadzawistowski]

Many videos seem to have completely arbitrary thumbnails which are not from the video. Most of the Epic Rap Battles videos, for example.

Perhaps this option 'unlocks' after you reach a certain subscriber count.

[JoshTriplett]

As mentioned upthread:

> partnered accounts are allowed to upload custom thumbnails (which can be any image, not necessarily even a screenshot from the video).