MESourceStarted event

Raised when a media source starts without seeking.

Event values

Possible values retrieved from IMFMediaEvent::GetValue include the following.

VARTYPE Description
No event data. The start time was from the current position.

The starting time, in 100-nanosecond units, relative to the time stamps on the samples.


The following attributes are defined for this event.

Attribute Description
Start time. The media source sets this attribute if it restarts from its current position.

Specifies whether the current segment topology is empty. The sequencer source sets this attribute.

Start time for a segment, relative to the start of the presentation. The sequencer source sets this attribute.


A media source raises this event when it starts from a stopped state, or starts from a paused state at the same position in the source. The event is raised if the IMFMediaSource::Start method returns S_OK.

If the media source starts from the current position and the source's previous state was running or paused, the event data can empty (VT_EMPTY). If the event data is VT_EMPTY, the media source might set the MF_EVENT_SOURCE_ACTUAL_START attribute with the actual starting time.

If the media source starts from a new position, or the source's previous state was stopped, the event data must be the starting time (VT_I8).

If the Start method causes a seek, the media source sends the MESourceSeeked event instead of MESourceStarted.


Requirement Value
Minimum supported client
Windows Vista [desktop apps only]
Minimum supported server
Windows Server 2008 [desktop apps only]
Mfobjects.h (include Mfidl.h)

See also

Media Foundation Events