Video visible when cb_component_state is 4

I’ve seen there is a delay between the time a stream is subscribed and the
time the video is actually visible. This happens when the
cb_component_state becomes 4. Is this associated with the stream? If so, is
there an event that is called when this field is changed to know when this
becomes 4? This is very useful when a developer wants to display the stream
that is already working.