CPosPassThru Class (Windows CE 5.0)

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This class is a utility class that handles the IMediaPosition and IMediaSeeking interfaces for single-input pin renderers and transform filters.

IMediaPosition is the interface originally used for seeking in time-based media streams. IMediaSeeking is an interface intended to replace IMediaPosition in filter graphs that require seeking to units other than time, such as samples or fields, or that require more precise time-based seeking.

Renderers will use this class to implement IMediaPosition and IMediaSeeking from the filter; transform filters will use it to implement these two interfaces from the output pin.

In both cases, the methods will be implemented by calls to the IMediaPosition or IMediaSeeking interface provided by the output pin of the connected upstream filter, effectively passing the position information through to the next filter.

Create a class derived from CPosPassThru, giving it the IPin pointer to your input pin, and delegate all IMediaPosition and IMediaSeeking methods to it.

The class will find the output pin connected to the input pin, query this output pin for the IMediaPosition or IMediaSeeking interface, and respond appropriately.

Protected Data Members

Member Description
m_Pin Pointer to the input pin of the filter.

Member Functions

Member function Description
CPosPassThru Constructs a CPosPassThru object.
ForceRefresh Releases any cached interfaces held on the upstream pin.

Overrideable Member Functions

Member function Description
GetMediaTime Retrieves the starting and ending media times.

Implemented IMediaPosition Methods

Method Description
CanSeekBackward Determines if the current position can be moved backward in the media stream.
CanSeekForward Determines if the current position can be moved forward in the media stream.
get_CurrentPosition Retrieves the current position in terms of the total length of the media stream.
get_Duration Retrieves the total duration of the media stream.
get_PrerollTime Retrieves the time before the start position that the filter graph will start any nonrandom access device rolling.
get_Rate Retrieves the playback rate, relative to normal playback of the media.
get_StopTime Retrieves the position within the media at which playback should stop.
put_CurrentPosition Sets the position within the media at which playback should start.
put_PrerollTime Sets the time before the start position that the filter graph will start any nonrandom access device rolling.
put_Rate Sets the playback rate, relative to normal playback of the media.
put_StopTime Sets the position within the media at which playback should stop.

Implemented IMediaSeeking Methods

Method Description
CheckCapabilities Determines which capabilities exist on a media stream by applying seeking capability flags and checking the returned value.
ConvertTimeFormat Converts a time from one time format to another.
GetAvailable Returns the range of times in which seeking is efficient.
GetCapabilities Retrieves the seeking capabilities of the media stream.
GetCurrentPosition Retrieves the current position within the media stream.
GetDuration Retrieves the length of time that the media stream will play.
GetPositions Retrieves the current start and stop position settings.
GetPreroll Retrieves the preroll settings.
GetRate Retrieves the current rate.
GetStopPosition Retrieves the position at which the media stream stops.
GetTimeFormat Retrieves the current media time format.
IsFormatSupported Determines if a specified time format is supported.
IsUsingTimeFormat Determines if the time format being used in the call is the same as the one the interface currently uses.
QueryPreferredFormat Retrieves the preferred time format the interface will use.
SetPositions Sets current and stop positions and applies flags to both.
SetRate Sets a new playback rate.
SetTimeFormat Sets the time format, which determines the format of units used during seeking.

Implemented INonDelegatingUnknown Methods

Method Description
NonDelegatingQueryInterface Returns a specified reference-counted interface.

Requirements

DirectShow applications and DirectShow filters have different include file and link library requirements.

For more information, see Setting Up the Build Environment.

OS Versions: Windows CE 2.12 and later. Version 2.12 requires DXPAK 1.0 or later.
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