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MFT_OUTPUT_DATA_BUFFER structure (mftransform.h)

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Contains information about an output buffer for a Media Foundation transform. This structure is used in the IMFTransform::ProcessOutput method.

Syntax

typedef struct _MFT_OUTPUT_DATA_BUFFER {
  DWORD         dwStreamID;
  IMFSample     *pSample;
  DWORD         dwStatus;
  IMFCollection *pEvents;
} MFT_OUTPUT_DATA_BUFFER, *PMFT_OUTPUT_DATA_BUFFER;

Members

dwStreamID

Output stream identifier. Before calling ProcessOutput, set this member to a valid stream identifier.

Exception: If the IMFTransform::GetStreamIDs method returns E_NOTIMPL, the MFT ignores this member and uses the indexes of the pOutputSamples array in the ProcessOutput method as the stream identifiers. In other words, it uses the first element in the array for stream 0, the second for stream 1, and so forth. It is recommended (but not required) that the caller set dwStreamID equal to the array index in this case.

pSample

Pointer to the IMFSample interface. Before calling ProcessOutput, set this member equal to a valid IMFSample pointer or NULL. See Remarks for more information.

dwStatus

Before calling ProcessOutput, set this member to zero. When the method returns, the MFT might set the member equal to a value from the _MFT_OUTPUT_DATA_BUFFER_FLAGS enumeration. Otherwise, the MFT leaves this member equal to zero.

pEvents

Before calling ProcessOutput, set this member to NULL. On output, the MFT might set this member to a valid IMFCollection interface pointer. The pointer represents a collecton that contains zero or more events. To get each event, call IMFCollection::GetElement and query the returned IUnknown pointer for the IMFMediaEvent interface. When the ProcessOutput method returns, the caller is responsible for releasing the IMFCollection pointer if the pointer is not NULL.

Remarks

You must provide an MFT_OUTPUT_DATA_BUFFER structure for each selected output stream.

MFTs can support two different allocation models for output samples:

  • The MFT allocates the output sample.
  • The client allocates the output sample.
To find which model the MFT supports for a given output stream, call IMFTransform::GetOutputStreamInfo and check the value of dwFlags.
Flag Allocation Model
MFT_OUTPUT_STREAM_PROVIDES_SAMPLES The MFT allocates the output samples for the stream. Set pSample to NULL for this stream.
MFT_OUTPUT_STREAM_CAN_PROVIDE_SAMPLES The MFT supports both allocation models.
Neither (default) The client must allocate the output samples for the stream.
 

The behavior of ProcessOutput depends on the initial value of pSample and the value of the dwFlags parameter in the ProcessOutput method.

  • If pSample is NULL and dwFlags contains the MFT_PROCESS_OUTPUT_DISCARD_WHEN_NO_BUFFER flag, the MFT discards the output data.

    Restriction: This output stream must have the MFT_OUTPUT_STREAM_DISCARDABLE or MFT_OUTPUT_STREAM_LAZY_READ flag. (To get the flags for the output stream, call the IMFTransform::GetOutputStreamInfo method.)

  • If pSample is NULL and dwFlags does not contain the MFT_PROCESS_OUTPUT_DISCARD_WHEN_NO_BUFFER, the MFT provides a sample for the output data. The MFT sets pSample to point to the sample that it provides. The MFT can either allocate a new sample or re-use an input sample.

    Restriction: This output stream must have the MFT_OUTPUT_STREAM_PROVIDES_SAMPLES or MFT_OUTPUT_STREAM_CAN_PROVIDE_SAMPLES flag.

  • If pSample is non-NULL, the MFT uses the sample provided by the caller.

    Restriction: This output stream must not have the MFT_OUTPUT_STREAM_PROVIDES_SAMPLES flag.

Any other combinations are invalid and cause ProcessOutput to return E_INVALIDARG.

Each call to ProcessOutput can produce zero or more events and up to one sample per output stream.

Requirements

Requirement Value
Minimum supported client Windows Vista [desktop apps | UWP apps]
Minimum supported server Windows Server 2008 [desktop apps | UWP apps]
Header mftransform.h

See also

IMFTransform::ProcessOutput

Media Foundation Structures

Media Foundation Transforms