When playing complex media, each sound and video sample must be played in a specific order at a specific time. For this purpose, GStreamer provides a synchronization mechanism.
Time in GStreamer is defined as the value returned from a particular
GstClock object from the method
In a typical computer, there are many sources that can be used as a
time source, e.g., the system time, soundcards, CPU performance
counters, ... For this reason, there are many
GstClock implementations available in GStreamer.
The clock time doesn't always start from 0 or from some known value.
Some clocks start counting from some known start date, other clocks start
counting since last reboot, etc...
As clocks return an absolute measure of time, they are not usually used directly. Instead, differences between two clock times are used to measure elapsed time according to a clock.