IMFMediaSession::Start method (mfidl.h)

Article
10/13/2021

Starts the Media Session.

Syntax

HRESULT Start(
  [in] const GUID        *pguidTimeFormat,
  [in] const PROPVARIANT *pvarStartPosition
);

Parameters

[in] pguidTimeFormat

Pointer to a GUID that specifies the time format for the pvarStartPosition parameter. This parameter can be NULL. The value NULL is equivalent to passing in GUID_NULL.

The following time format GUIDs are defined:

Value	Meaning
GUID_NULL	Presentation time. The pvarStartPosition parameter must have one of the following PROPVARIANT types. VT_I8: The pvarStartPosition parameter contains the starting position in 100-nanosecond units, relative to the start of the presentation. VT_EMPTY: Playback starts from the current position. All media sources support this time format.
MF_TIME_FORMAT_SEGMENT_OFFSET	Segment offset. This time format is supported by the Sequencer Source. The starting time is an offset within a segment. Call the MFCreateSequencerSegmentOffset function to create the PROPVARIANT value for the pvarStartPosition parameter.
MF_TIME_FORMAT_ENTRY_RELATIVE	Note Requires Windows 7 or later. Skip to a playlist entry. The pvarStartPosition parameter specifies the index of the playlist entry, relative to the current entry. For example, the value 2 skips forward two entries. To skip backward, pass a negative value. The PROPVARIANT type is VT_I4. If a media source supports this time format, the IMFMediaSource::GetCharacteristics method returns one or both of the following flags: MFMEDIASOURCE_CAN_SKIPFORWARD MFMEDIASOURCE_CAN_SKIPBACKWARD

Value

Meaning

GUID_NULL

Presentation time. The pvarStartPosition parameter must have one of the following PROPVARIANT types.

VT_I8: The pvarStartPosition parameter contains the starting position in 100-nanosecond units, relative to the start of the presentation.
VT_EMPTY: Playback starts from the current position.

All media sources support this time format.

MF_TIME_FORMAT_SEGMENT_OFFSET

Segment offset. This time format is supported by the Sequencer Source. The starting time is an offset within a segment.

Call the MFCreateSequencerSegmentOffset function to create the PROPVARIANT value for the pvarStartPosition parameter.

MF_TIME_FORMAT_ENTRY_RELATIVE

Note Requires Windows 7 or later.

Skip to a playlist entry. The pvarStartPosition parameter specifies the index of the playlist entry, relative to the current entry. For example, the value 2 skips forward two entries. To skip backward, pass a negative value. The PROPVARIANT type is VT_I4.

If a media source supports this time format, the IMFMediaSource::GetCharacteristics method returns one or both of the following flags:

MFMEDIASOURCE_CAN_SKIPFORWARD
MFMEDIASOURCE_CAN_SKIPBACKWARD

[in] pvarStartPosition

Pointer to a PROPVARIANT that specifies the starting position for playback. The meaning and data type of this parameter are indicated by the pguidTimeFormat parameter.

Return value

The method returns an HRESULT. Possible values include, but are not limited to, those in the following table.

Return code	Description
S_OK	The method succeeded.
MF_E_INVALIDREQUEST	The operation cannot be performed in the Media Session's current state.
MF_E_SHUTDOWN	The Media Session has been shut down.

Remarks

When this method is called, the Media Session starts the presentation clock and begins to process media samples.

This method is asynchronous. When the method completes, the Media Session sends an MESessionStarted event.

Requirements

Requirement	Value
Minimum supported client	Windows Vista [desktop apps only]
Minimum supported server	Windows Server 2008 [desktop apps only]
Target Platform	Windows
Header	mfidl.h
Library	Mfuuid.lib