CSourceSeeking Class (Compact 2013)

Article
01/31/2017

3/26/2014

** CSourceSeeking Class**

This is an abstract class that assists source filters with the implementation of IMediaSeeking interface methods. This class enables a source filter to handle calls that change the start and stop positions in the media stream and the playback rate.

Derive from this class and set the positions.

This class supports IMediaSeeking, and calls the pure virtual member functions CSourceSeeking::ChangeStart, CSourceSeeking::ChangeStop, and CSourceSeeking::ChangeRate when CSourceSeeking::SetPositions or CSourceSeeking::SetRate is called, to enable a source filter to handle these commands and start sending new data.

Override the CSourceSeeking::ChangeStart, CSourceSeeking::ChangeStop, and CSourceSeeking::ChangeRate member functions to do something when the properties change.

Protected Data Members

Member	Description
m_dRateSeeking	Playback rate. Set to 1 by default.
m_dwSeekingCaps	Seeking capabilities returned in the GetCapabilities function. Can be one or more of the following values: AM_SEEKING_CanSeekForwards AM_SEEKING_CanSeekBackwards AM_SEEKING_CanSeekAbsolute AM_SEEKING_CanGetStopPos AM_SEEKING_CanGetDuration. Set to all of these by default.
m_pLock	Pointer to a CCritSec object for locking.
m_rtDuration	Duration of the stream. Set to m_rtStop by default.
m_rtStart	Start time. Set to zero by default.
m_rtStop	Stop time. Set to the largest positive 64-bit integer possible (9223372036854775807) by default.

Member Functions

Member function	Description
CSourceSeeking	Constructs a CSourceSeeking object.

Overrideable Member Functions

Member function	Description
ChangeRate	Override this pure virtual to handle notification of a change of sample rate.
ChangeStart	Override this pure virtual to handle notification of a change of start time.
ChangeStop	Override this pure virtual to handle notification of a change in stop time.

Implemented IMediaSeeking Methods

Method	Description
CheckCapabilities	Checks that all requested capabilities are in m_dwSeekingCaps.
ConvertTimeFormat	Checks that the time format is TIME_FORMAT_MEDIA_TIME. This is the only format currently available.
GetAvailable	Retrieves the range of seeking times. Earliest is zero and latest is the media stream's duration.
GetCapabilities	Retrieves the current seeking capabilities in m_dwSeekingCaps.
GetCurrentPosition	Not currently implemented.
GetDuration	Retrieves the length of time the media stream will play.
GetPositions	Retrieves the current start and stop position settings.
GetPreroll	Sets the preroll time to zero.
GetRate	Retrieves the current playback rate.
GetStopPosition	Retrieves the position within the media stream at which playback should stop.
GetTimeFormat	Sets the time format to TIME_FORMAT_MEDIA_TIME. This is the only format currently supported.
IsFormatSupported	Determines if the requested format is TIME_FORMAT_MEDIA_TIME. This is the only format currently supported.
IsUsingTimeFormat	Determines if the requested format is TIME_FORMAT_MEDIA_TIME. This is the only format supported.
QueryPreferredFormat	Sets the preferred time format to TIME_FORMAT_MEDIA_TIME. This is the only format supported.
SetPositions	Sets current and stop positions, first checking that the seeking options are valid.
SetRate	Sets the playback rate.
SetTimeFormat	Checks that the time format is TIME_FORMAT_MEDIA_TIME. This is the only format supported.

Implemented INonDelegatingUnknown Methods

Method	Description
NonDelegatingQueryInterface	Retrieves an interface and increments the reference count on the interface.

Requirements

Header	dshow.h, Streams.h
Library	ole32.lib, Ole32auth.lib, Strmbase.lib, Strmiids.lib, uuid.lib