IMFByteStreamHandler::BeginCreateObject method (mfidl.h)

Begins an asynchronous request to create a media source from a byte stream.

Syntax

HRESULT BeginCreateObject(
  [in]  IMFByteStream    *pByteStream,
  [in]  LPCWSTR          pwszURL,
  [in]  DWORD            dwFlags,
  [in]  IPropertyStore   *pProps,
  [out] IUnknown         **ppIUnknownCancelCookie,
  [in]  IMFAsyncCallback *pCallback,
  [in]  IUnknown         *punkState
);

Parameters

[in] pByteStream

Pointer to the byte stream's IMFByteStream interface.

[in] pwszURL

String that contains the original URL of the byte stream. This parameter can be NULL.

[in] dwFlags

Bitwise OR of zero or more flags. See Source Resolver Flags.

[in] pProps

Pointer to the IPropertyStore interface of a property store. The byte-stream handler can use this property store to configure the object. This parameter can be NULL. For more information, see Configuring a Media Source.

[out] ppIUnknownCancelCookie

Receives an IUnknown pointer or the value NULL. If the value is not NULL, you can cancel the asynchronous operation by passing this pointer to the IMFByteStreamHandler::CancelObjectCreation method. The caller must release the interface. This parameter can be NULL.

[in] pCallback

Pointer to the IMFAsyncCallback interface of a callback object. The caller must implement this interface.

[in] punkState

Pointer to the IUnknown interface of a state object, defined by the caller. This parameter can be NULL. You can use this object to hold state information. The object is returned to the caller when the callback is invoked.

Return value

The method returns an HRESULT. Possible values include, but are not limited to, those in the following table.

Remarks

The dwFlags parameter must contain the MF_RESOLUTION_MEDIASOURCE flag and should not contain the MF_RESOLUTION_BYTESTREAM flag.

The byte-stream handler is responsible for parsing the stream and validating the contents. If the stream is not valid or the byte stream handler cannot parse the stream, the handler should return a failure code. The byte stream is not guaranteed to match the type of stream that the byte handler is designed to parse.

If the pwszURL parameter is not NULL, the byte-stream handler might use the URL during the resolution process. (For example, it might use the file name extension, if present.) Also, the byte stream might contain the MF_BYTESTREAM_CONTENT_TYPE attribute, specifying the MIME type.

When the operation completes, the byte-stream handler calls the IMFAsyncCallback::Invoke method. The Invoke method should call IMFByteStreamHandler::EndCreateObject to get a pointer to the media source.

Requirements

See also

IMFByteStreamHandler

Scheme Handlers and Byte-Stream Handlers