Javadoc
Returns a list with with specific meta information like
width/height/framerate of video streams or samplerate/number of channels of
audio streams. This stream information from the "stream-info" property is
best queried once playbin has changed into PAUSED or PLAYING state (which
can be detected via a state-changed message on the GstBus where
old_state=READY and new_state=PAUSED), since before that the list might not
be complete yet or not contain all available information (like
language-codes).