GStreamer can use different clocks. Though the system time can be used
as a clock, soundcards and other devices provides a better time source. For
this reason some elements provide a clock. The method
get_clock
is implemented in elements that provide
one.
As clocks return an absolute measure of time, they are not usually used directly. Instead, a reference to a clock is stored in any element that needs it, and it is used internaly by GStreamer to calculate the element time.