Gets the state of the element.
For elements that performed an ASYNC state change, as reported by Element.setState, this function will block up to the specified timeout value for the state change to complete. If the element completes the state change or goes into an error, this function returns immediately with a return value of GST_STATE_CHANGE_SUCCESS or GST_STATE_CHANGE_FAILURE respectively.
For elements that did not return GST_STATE_CHANGE_ASYNC, this function returns the current and pending state immediately.
This function returns GST_STATE_CHANGE_NO_PREROLL if the element successfully changed its state but is not able to provide data yet. This mostly happens for live sources that only produce data in GST_STATE_PLAYING. While the state change return is equivalent to GST_STATE_CHANGE_SUCCESS, it is returned to the application to signal that some sink elements might not be able to complete their state change because an element is not producing data to complete the preroll. When setting the element to playing, the preroll will complete and playback will start.
a pointer to GstState to hold the state. Can be NULL.
a pointer to GstState to hold the pending state. Can be NULL.
a GstClockTime to specify the timeout for an async state change or GST_CLOCK_TIME_NONE for infinite timeout.
GST_STATE_CHANGE_SUCCESS if the element has no more pending state and the last state change succeeded, GST_STATE_CHANGE_ASYNC if the element is still performing a state change or GST_STATE_CHANGE_FAILURE if the last state change failed.