Documentation are the paria of the free software movement. The thing is, you know you need them, but you don’t want to write them since it takes time. In the end, you spend 10x as much time explaining various things to people. And then you decide to write docs anyway. And then people rewrite stuff and it all falls apart.
Today, I uploaded a first version of a largely rewritten GStreamer Application Development Manual. Many parts need lots of work, but some parts are already useful (e.g. part2, the first chapters of part3 and the first two sections of part4). Feel the love.