That looks pretty awesome for a first roast!
First crack is quite audible generally and second crack much quieter. The crinkling cellophane is a good analogy.
I only used a popper once many many years ago and I am sure the neighbours were ready to call the fire brigade! It happens a lot quicker in a popper and I guess first crack would be around 5 to 10 mins, second crack a few minutes post first crack? I am sure the regular poppers will chime in with info.
Enjoy the bug!!