The METransformHaveOutput event indicates that a device transform has a sample ready on one of its output streams.
發送時
當 Devproxy 或裝置 MFT 在其輸出資料流程上準備好範例以由裝置轉換管理員 （DTM） 挑選時，就會引發此事件。
當 Devproxy 引發 METransformHaveOutput 時，DTM 會在 Devproxy 上呼叫 ProcessOutput。 產生的範例會饋送至裝置 MFT 的對應輸入。
When Device MFT raises METransformHaveOutput, DTM would relay the event to Device Source. 裝置來源會在裝置轉換管理員上呼叫進程輸出，該程式會路由傳送至裝置 MFT。 因此，裝置來源會挑選範例，並進入媒體管線。
參數
None.
Remarks
Device MFT would receive the total output stream count of MFT_OUTPUT_DATA_BUFFER structures in an array. 預期會以適當的值填入結構成員。 Before DTM calls back into the Device MFT to retrieve a sample, in response to a METransformHaveOutput message, if another sample becomes available for another stream, Device MFT would go ahead and send the sample in this ProcessOutput call. DTM 會再次呼叫 ProcessOutput，但此時，如果沒有可用的範例，裝置 MFT 可以只傳回沒有範例的呼叫。
For more information, see IMFDeviceTransform::ProcessOutput.