Comment 4 for bug 1563056

It should be possible in JavaScript. The performance bottleneck of this problem is probably in converting the video images to a brightness value. It should be possible to speed up this step by taking lower quality images (resolution/bit-rate) or/and by reducing the frame-rate.

- I was using 1280 x 720 (6499 kbps) at 30fps
- 300bpm correspond to 5Hz -> 10fps should be enough
- Running the script on a down-sampled video of 1280 x 720 (958 kbps) at 10fps yields very similar results (should go through more thorough testing and films of finger just after effort (higher bpm))