question on when sink element send message to motify state playing to paused complete?

[bcxa sz]

Hi Developers,

when change the playbin2 pipeline from playing to paused, the sink
element will change state from playing to paused asynchronously. My
question is when the sink element complete the state change? The data
pre-rolled? How to know the data has been pre-rolled? The queued data
reach one pre-defined buffer level? what's the value of this buffer
level?

best regards