What is the duration of the 3 flashes? I sampled a few ( two shown here) using Limovie and obtained the similar timing using PAL frame rate. 30 frames duration or 30x4/100 or 1.2 seconds. The peak height correspond to the brightness. Next will be those odd filler - continuous blocks of ~6 flashes.
Another pass of EGP tonite. Click the images and find the variations of group of flashes. The common 3s, and the long blocks with very close timings. EGP - the disco-ball - check out this image .