CMediaSample Class

Article
11/18/2015

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4/8/2010

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This class represents a buffer object that supports the IMediaSample interface. It represents a buffer in memory, together with some associated properties stored as protected data members.

The constructor is passed as a pointer to the buffer with its length in bytes; other properties are normally set and accessed through implemented IMediaSample interface methods.

These properties describe various attributes of the media sample, such as the sample's media type, start and end time, and options.

The options can include whether the media sample is a sync point, a preroll sample, or discontinuous with other samples.

All member functions in this class that return HRESULT and accept a pointer as a parameter return E_POINTER when passed a null pointer.

Protected Data Members

Member	Description
m_cbBuffer	Size of the buffer.
m_dwFlags	Sample property flags as follows: Sample_Discontinuity: Set if start of a new segment. Sample_MediaTimeValid: Set if the media time is valid. Sample_Preroll: Set if sample is a preroll sample. Sample_StopValid: Set if the stop time is valid. Sample_SyncPoint: Set if sample is a synchronization point. Sample_TimeValid: Set if the time is valid. Sample_TypeChanged: Set if the type has changed.
m_End	Sample end time.
m_lActual	Actual length of data in this sample.
m_MediaEnd	Media end (offset from m_MediaStart).
m_MediaStart	Media start position.
m_pAllocator	Pointer to the IMemAllocator object associated with this object.
m_pBuffer	Pointer to the complete buffer.
m_pMediaType	Pointer to a structure containing the media type of the sample.
m_pNext	Pointer to the next CMediaSample object in the free list.
m_Start	Sample start time.

Member Functions

Member function	Description
CMediaSample	Constructs a CMediaSample object.
SetPointer	Sets the buffer pointer and length.

Implemented IUnknown Methods

Method	Description
QueryInterface	Retrieves pointers to supported interfaces.
AddRef	Increments the reference count.
Release	Decrements the reference count.

Implemented IMediaSample Methods

Method	Description
GetActualDataLength	Retrieves the data length of the sample.
GetMediaTime	Retrieves the media time extents of the sample.
GetMediaType	Retrieves the media type of the CMediaSample object.
GetPointer	Retrieves a read/write pointer to the memory of this buffer.
GetSize	Returns the size, in bytes, of the buffer data area.
GetTime	Sets the media time extents for this sample.
IsDiscontinuity	Determines if there is discontinuity in the data stream.
IsPreroll	Indicates a preroll property. If TRUE, this sample is for preroll only and should not be displayed.
IsSyncPoint	Determines if the beginning of a sample is a synchronization point.
SetActualDataLength	Sets the data length of the sample.
SetDiscontinuity	Sets the discontinuity property.
SetMediaTime	Sets the media time of the CMediaSample object.
SetMediaType	Sets the media type of the CMediaSample object.
SetPreroll	Sets preroll property. If TRUE, this sample is for preroll only and should not be displayed.
SetSyncPoint	Sets sync-point property.
SetTime	Sets the stream time at which this sample should start and finish.

Implemented INonDelegatingUnknown Methods

Method	Description
NonDelegatingQueryInterface	Passes out pointers to any interfaces added to the derived filter class.

Requirements

Windows Embedded CE	Windows CE 2.12 and later
Windows Mobile	Windows Mobile Version 5.0 and later
Note	Microsoft DirectShow applications and DirectShow filters have different include file and Library requirements For more information, see Setting Up the Build Environment

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