Time Slicing

Not in the cool Terry Pratchet “Theif of Time” way. More in the “messing-around-with-video-to-get-funny-effects” way.

So imagine video as a set of still images. Then imagine stacking these pictures one in-front of the other. In order to play the video you would have to start at the front of the stack and move backwards making each of the images totally transparent.

Now take that same stack of images, rotate it 90 degrees about the y axis so your looking at them side on (The x axis and time axis have now swapped round). Then take slices through this. You have now time sliced!

Illustration of rotating the "image stack"

Hold onto your hats because heres a video of this in action:

What can this be used for you may be asking? Well if you run a horizontal sobel filter over the individual time sliced frames you have a “rate-of-change-with-time”  for each pixel.

Now take a feed from a camera. Stick the incoming frames onto a queue of a set size. time slice these frames. Do a sobel filter on them and then spin em back to normal and compress all the frames into a single frame (do the average or just take one of them or something). Then use this single frame as an alpha channel mask. This will give you a sort-of-temporally-adjusting-background-subtraction-type-thing.


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