DirectShow

https://docs.microsoft.com/en-us/windows/win32/directshow/directshow

https://docs.microsoft.com/en-us/windows/win32/directshow/filter-states

Filters have three possible states: stopped, paused, and running FILTER_STATE

Transitions between stopped and running always go through the paused state, so if the application calls Run on a stopped graph, the Filter Graph Manager pauses the graph before running it. 即每次 running 状态前必定有 paused 状态，包括初次点开始播放时

The Filter Graph Manager carries out all state transitions in upstream order, starting from the renderer and working backward to the source filter. FGM 控制各 Filter 的状态的顺序是从最下游的渲染层开始，再依次回到最上游资源filter。实时流数据例外

https://docs.microsoft.com/en-us/windows/win32/directshow/retrieving-events