Reference Clock

In the explanation of this SDK, I see there are some clock implementations such as Extended Reference Clock. What is the main difference between your clock and other clocks such as video card's reference clock? What are the main advantageous of this clock?

Video card hasn't reference clock.

Reference clock from audio card is used as default Reference clock for play files. If audio render not included into graph, then will be used default implementation of Reference clock from Graph manager object. In some cases extern Reference clock is very useful. For sample, if audio render not not included into graph, then you can implement very smooth playback speed changing with minimal development. Class CRefClockSpeed can be used for it.