Hello there,
This can be of any source but it must meet the below conditions.
An application that uses the Media Session should never start, stop, or pause the presentation clock; change the clock rate; or shut down the clock.
To get a pointer to the presentation clock, call IMFMediaSession::GetClock on the Media Session. The presentation clock does not return a valid time until the Media Session sends the MESessionTopologyStatus event with the MF_TOPOSTATUS_READY flag. Until then, GetClock returns MF_E_CLOCK_NO_TIME_SOURCE.
Hope this resolves your Query !!
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