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UID title description helpviewer_keywords old-location tech.root ms.assetid ms.date ms.keywords req.header req.include-header req.target-type req.target-min-winverclnt req.target-min-winversvr req.kmdf-ver req.umdf-ver req.ddi-compliance req.unicode-ansi req.idl req.max-support req.namespace req.assembly req.type-library req.lib req.dll req.irql targetos req.typenames req.redist ms.custom f1_keywords dev_langs topic_type api_type api_location api_name
NF:mfidl.IMFClockStateSink.OnClockStart
IMFClockStateSink::OnClockStart (mfidl.h)
Called when the presentation clock starts.
1a696ffc-b8e6-4ef9-b980-35bfbd3d4128
IMFClockStateSink interface [Media Foundation]
OnClockStart method
IMFClockStateSink.OnClockStart
IMFClockStateSink::OnClockStart
OnClockStart
OnClockStart method [Media Foundation]
OnClockStart method [Media Foundation]
IMFClockStateSink interface
mf.imfclockstatesink_onclockstart
mfidl/IMFClockStateSink::OnClockStart
mf\imfclockstatesink_onclockstart.htm
mf
1a696ffc-b8e6-4ef9-b980-35bfbd3d4128
12/05/2018
1a696ffc-b8e6-4ef9-b980-35bfbd3d4128, IMFClockStateSink interface [Media Foundation],OnClockStart method, IMFClockStateSink.OnClockStart, IMFClockStateSink::OnClockStart, OnClockStart, OnClockStart method [Media Foundation], OnClockStart method [Media Foundation],IMFClockStateSink interface, mf.imfclockstatesink_onclockstart, mfidl/IMFClockStateSink::OnClockStart
mfidl.h
Windows
Windows Vista [desktop apps \| UWP apps]
Windows Server 2008 [desktop apps \| UWP apps]
Mfuuid.lib
Windows
19H1
IMFClockStateSink::OnClockStart
mfidl/IMFClockStateSink::OnClockStart
c++
APIRef
kbSyntax
COM
mfuuid.lib
mfuuid.dll
IMFClockStateSink.OnClockStart

IMFClockStateSink::OnClockStart

-description

Called when the presentation clock starts.

-parameters

-param hnsSystemTime [in]

The system time when the clock started, in 100-nanosecond units.

-param llClockStartOffset [in]

The new starting time for the clock, in 100-nanosecond units. This parameter can also equal PRESENTATION_CURRENT_POSITION, indicating the clock has started or restarted from its current position.

-returns

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

-remarks

This method is called when the presentation clock's IMFPresentationClock::Start method is called, with the following exception: If the clock is paused and Start is called with the value PRESENTATION_CURRENT_POSITION, IMFClockStateSink::OnClockRestart is called instead of OnClockStart.

The clock notifies the presentation time source by calling the time source's OnClockStart method. This call occurs synchronously within the Start method. If the time source returns an error from OnClockStart, the presentation clock's Start method returns an error and the state change does not take place.

For any object that is not the presentation time source, the OnClockStart method is called asynchronously, after the state change is completed. In that case, the return value from this method is ignored.

The value given in llClockStartOffset is the presentation time when the clock starts, so it is relative to the start of the presentation. Media sinks should not render any data with a presentation time earlier than llClockStartOffSet. If a sample straddles the offset—that is, if the offset falls between the sample's start and stop times—the sink should either trim the sample so that only data after llClockStartOffset is rendered, or else simply drop the sample.

-see-also

IMFClockStateSink

MFTIME

Presentation Clock