CSourceStream Class

Derive from this class to provide a class that creates the data stream from one of the output pins. It should be used with an object that is derived from the CSource class derived object to provide the filter-level object.

The CSourceStream class creates a worker thread to push data downstream when the filter enters a paused or running state. The thread first calls the CSourceStream::OnThreadCreate member function. If this succeeds, it will loop, calling the CSourceStream::FillBuffer member function until the CSourceStream::Inactive member function stops it. As the thread quits, it calls the CSourceStream::OnThreadDestroy member function. If OnThreadCreate fails, OnThreadDestroy is called, and the active member function will fail.

To use the CSourceStream class, supporting a single media type, carry out the following steps.

1. Override the CSourceStream::GetMediaType member function to report the supported output format.
2. Override the CSourceStream::FillBuffer member function with a means of filling out each IMediaSample object with data.

To use the CSourceStream class, supporting multiple media types, carry out the following.

1. Override the CSourceStream::CheckMediaType and CSourceStream::GetMediaType member functions to report the supported media types (for more information, see the CBaseMediaFilter class).
2. Override the CSourceStream::FillBuffer member function with a means of filling out each IMediaSample object with data.

See SAMPLES\DS\BALL in the Microsoft® DirectShow™ SDK Software Development Kit (SDK) for an example of a pin supporting multiple types.

If you want more complex management of your worker thread, you can override most of the associated member functions. See Samples\DS\Vidcap in the Microsoft DirectX Media Software Development Kit (SDK) for an example.

Member Functions

Name	Description
Active	Called by the CBaseMediaFilter class to start the worker thread.
CheckRequest	Determines if a command is waiting for the thread.
CSourceStream	Constructs a CSourceStream object.
Exit	Called by the CSourceStream::Inactive member function to exit the worker thread.
GetRequest	Retrieves the next command for the thread.
Inactive	Called by the CBaseMediaFilter member function to shut down the worker thread.
Init	Called by the CSourceStream::Active member function to initialize the worker thread.
Pause	Pauses the stream of the worker thread. This will acquire all necessary resources.
Run	Starts the worker thread generation of a media sample stream.
Stop	Stops the stream.

Overridable Member Functions

Name	Description
CheckMediaType	Determines if a specific media type is supported. Override this member function if you use multiple types.
DoBufferProcessingLoop	Loops, collecting a buffer and calling the CSourceStream::FillBuffer processing function.
FillBuffer	Override this member function to fill the stream buffer during the creation of a media sample.
GetMediaType	Retrieves the media type or types that this pin supports; override the appropriate version of this member function to support one or multiple media types.
OnThreadCreate	Called as the worker thread is created; override this member function for special processing.
OnThreadDestroy	Called during the destruction of a worker thread; override this member function for special processing.
OnThreadStartPlay	Called at the start of processing Pause or Run command; override this member function for special processing.
ThreadProc	Override this member function to create a custom thread procedure.

Implemented IPin Methods

Name	Description
QueryId	Retrieves an identifier for the pin.

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CSourceStream::Active

CSourceStream Class

Starts the worker thread.

HRESULT Active(void);

Return Values

Returns an HRESULT, which can be one of the following:

Value	Meaning
E_FAIL	Thread could not start.
S_FALSE	Pin is already active.
S_OK	Thread was started successfully.

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CSourceStream::CheckMediaType

CSourceStream Class

Determines if this pin supports the supplied media type.

virtual HRESULT CheckMediaType(
  CMediaType *pMediaType
  );

Parameters

pMediaType

Media type to check.

Return Values

Returns S_OK if the media type is supported, S_FALSE if it isn't, or E_INVALIDARG if pMediaType is invalid.

Remarks

Override this member function if you support multiple media types. Test explicitly for S_OK to determine if this function succeeded; do not use the SUCCEEDED macro.

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CSourceStream::CheckRequest

CSourceStream Class

Determines if a command is waiting for the thread.

BOOL CheckRequest(
  Command *pCom
  );

Parameters

pCom

Pointer to the location to which to return a command, if any.

Return Values

Returns TRUE if the pCom parameter contains a command; otherwise, returns FALSE.

Remarks

This member function does not block. This is a type safe override of the method in the CAMThread class.

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CSourceStream::CSourceStream

CSourceStream Class

Creates a CSourceStream object.

CSourceStream(
  TCHAR *pObjectName,
  HRESULT *phr,
  CSource *pms,
  LPCWSTR pName
  );

Parameters

pObjectName

Name of the object.

phr

Resulting value for this constructor.

pms

Pointer for the CSource object.

pName

Name of the pin.

Return Values

No return value.

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CSourceStream::DoBufferProcessingLoop

CSourceStream Class

Loops, collecting a buffer and calling the CSourceStream::FillBuffer processing function.

virtual HRESULT DoBufferProcessingLoop(void);

Return Values

Returns an HRESULT value.

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CSourceStream::Exit

CSourceStream Class

Causes the thread to exit.

HRESULT Exit(void);

Return Values

Returns NOERROR if the member function was received.

Remarks

If the thread returns an error, it sets the return value of the CSourceStream::ThreadProc member function.

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CSourceStream::FillBuffer

CSourceStream Class

Fills the stream buffer during the creation of a media sample that the current pin provides.

virtual HRESULT FillBuffer(
  IMediaSample *pSample
  ) PURE;

Parameters

pSample

IMediaSample buffer to contain the data.

Return Values

Returns an HRESULT value.

Remarks

The CSourceStream::ThreadProc member function calls the CSourceStream::FillBuffer member function. The derived class must supply an implementation of this member function.

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CSourceStream::GetMediaType

CSourceStream Class

Fills out the fields of the CMediaType object to the supported media type.

virtual HRESULT GetMediaType(
  int iPosition,
  CMediaType *pMediaType
  );

virtual HRESULT GetMediaType(
  CMediaType *pMediaType
  );

Parameters

iPosition

Position of the media type within a list of multiple media types. Range is zero through n.

pMediaType

Pointer to a CMediaType object to be set to the requested format.

Return Values

Returns one of the following HRESULT values.

Value	Meaning
Error Code	Media type could not be set.
S_FALSE	Media type exists but is not currently usable.
S_OK	Media type was set.
VFW_S_NO_MORE_ITEMS	End of the list of media types has been reached.

Remarks

This member function sets the requested media type. If only a single media type is supported, override this member function with the single-parameter definition. Only the default implementations of the CSourceStream::CheckMediaType and CSourceStream::GetMediaType member functions call the single media type member function.

Override the single-version GetMediaType or the two-parameter version, CheckMediaType.

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CSourceStream::GetRequest

CSourceStream Class

Retrieves the next command for the thread.

Command GetRequest(void);

Return Values

Returns the next command.

Remarks

This member function blocks until a command is available. It is a type safe override of the member function in the CAMThread class.

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CSourceStream::Inactive

CSourceStream Class

Identifies a pin as inactive and shuts down the worker thread.

HRESULT Inactive(void);

Return Values

Returns an HRESULT value, including the following values.

Value	Meaning
S_OK	Thread exited successfully.
S_FALSE	Pin is already inactive.

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CSourceStream::Init

CSourceStream Class

Initializes the worker thread.

HRESULT Init(void);

Return Values

Returns an HRESULT value, including the following values.

Value	Meaning
S_OK	Thread was initialized successfully.
S_FALSE	Thread was already initialized.

Remarks

The CSourceStream::Active member function calls this member function.

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CSourceStream::OnThreadCreate

CSourceStream Class

Starts or stops a process upon the creation of a thread.

virtual HRESULT OnThreadCreate(void);

Return Values

Returns an HRESULT value, including the following values.

Value	Meaning
NOERROR	No error occurred.
Error code	Thread should exit.

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CSourceStream::OnThreadDestroy

CSourceStream Class

Starts or stops a process upon the destruction of a thread.

virtual HRESULT OnThreadDestroy(void);

Return Values

Returns either NOERROR or an HRESULT value (greater than zero) that indicates an error.

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CSourceStream::OnThreadStartPlay

CSourceStream Class

Starts a process upon the beginning of the playing of the thread.

virtual HRESULT OnThreadStartPlay(void);

Return Values

Default implementation returns NOERROR.

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CSourceStream::Pause

CSourceStream Class

Pauses a media sample stream.

HRESULT Pause(void);

Return Values

Returns an HRESULT value, including the following value.

Value	Meaning
S_OK	Thread paused successfully.

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CSourceStream::Run

CSourceStream Class

Starts a media sample stream.

HRESULT Run(void);

Return Values

Returns S_OK if successful; otherwise, returns an HRESULT error value.

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CSourceStream::Stop

CSourceStream Class

Stops a media sample stream.

HRESULT Stop(void);

Return Values

Returns S_OK if successful; otherwise, returns an HRESULT error value.

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CSourceStream::ThreadProc

CSourceStream Class

Implements the thread procedure.

virtual DWORD ThreadProc(void);

Return Values

Returns 0 if the thread completed successfully and 1 otherwise. If 1, the thread's resources might still be allocated.

Remarks

When this member function returns, the thread exits. Override this member function if the provided version is not sophisticated enough.

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