Okay, I’ve just gone over the video in Sony Vegas, and I’m pretty sure I’ve got a good idea of how he did it – or at least, I’ve found a discontinuity in the video that would give a damned good suggestion of how he did it.
My theory is that it’s a simple split screen effect with some motion-following tech to give that authentic shakycam feel to it: from the moment the draw starts, the left hand side of the frame never changes. I’m pretty sure it’s held from the start of that sequence until about 6m07 seconds in, when the live version is cut back in. During the time it’s held, the balls are replaced by an assistant.
The smoking gun that the balls have been tampered with? Have a look at these framegrabs:
This one is from very near the start of the programme. Note that the top of the balls are aligned perfectly. But then, just before the point of his reveal, we have this:
The left-most ball is clearly raised up a small amount compared to the others. I’d suggest this pretty clearly indicates tampering, and I think I’ve spotted where the cut between the two sets of balls happens. Here is a frame from just before 6m07, showing the balls lined up nicely:
…and one from just after 6m07, where the leftmost ball is raised up slightly (you’ll have to squint a bit, and it’s much easier to see in a video editor if you scrub backwards and forwards):
So, there you go. That’s my theory, anyway. I guess we’ll find out tomorrow if I’m right or not.