Tools to analyze & graph the bitrate of movie?

I remember seeing some screenshots of some Quicktime utilities/apps that can display a bar graph of each frame's data size in a movie as well as the average bitrate (as well as other stats).

It was a good visual analysis to check where the data spikes as well as where keyframes are.

Can anyone point me in the right direction to such a tool?

(I know Quicktime Player displays an average data rate, but it's for the entire movie. I want to see specific time segments)