I am far from convinced that most people with an aptitude for scripting and programming[1] prefer videos as a means of instruction.
I, for one, would never use a video to learn a new programming language or toolkit. I don't have the patience to sit through screencasts featuring the excitement of... code. I can't use videos as reference material to look stuff up. They don't lend themselves well to display of code examples, particularly those of more than a few lines.
They are good for high-level project marketing, or for showcasing the use of an interactive application. Videos are a very inefficient vehicle for delivery of the kind of information relevant to gaining competency at Kamailio.
-- Alex
[1] Which is unquestionably required to use Kamailio; it's configured using a programmatic domain-specific language (DSL), and that's not going to change.