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MFSampleExtension_DeviceTimestamp does not contain documented QPC value RRS feed

  • Question

  • When capturing using AVstream (i.e connecting a USB camera) and reading samples using Media Foundation, the MFSampleExtension_DeviceTimestamp attribute does not contain a raw QPC value. The documentation for this attribute states: 

    "This attribute is set on media samples created by a media source for a capture device. This attribute carries the non-adjusted value of the query performance counter (QPC). This attribute is available for MFTs inserted into the capture pipeline.
    To get the time stamp relative to the start of streaming, call the IMFSample::GetSampleTime method."

    The timestamp value I get is the same as the one reported by GetSampleTime, which is a ref-time and not a raw QPC value. The raw QPC value at the same time is a completely different value on my computer. 

    Is it the documentation that is wrong, or is the AVstream capture driver faulty?

    Regards Björn

    Friday, October 26, 2018 12:45 PM