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Direct3D Device Manager

The Microsoft Direct3D device manager enables two or more objects to share the same Microsoft Direct3D 9 device. One object acts as the owner of the Direct3D 9 device. To share the device, the owner of the device creates the Direct3D device manager. Other objects can obtain a pointer to the device manager from the device owner, then use the device manager to get a pointer to the Direct3D device. Any object that uses the device holds an exclusive lock, which prevents other objects from using the device at the same time.

Note  The Direct3D Device Manager supports Direct3D 9 devices only. It does not support DXGI devices.

To create the Direct3D device manager, call DXVA2CreateDirect3DDeviceManager9. This function returns a pointer to the device manager's IDirect3DDeviceManager9 interface, along with a reset token. The reset token enables the owner of the Direct3D device to set (and reset) the device on the device manager. To initialize the device manager, call IDirect3DDeviceManager9::ResetDevice. Pass in a pointer to the Direct3D device, along with the reset token.

The following code shows how to create and initialize the device manager.


HRESULT CreateD3DDeviceManager(
    IDirect3DDevice9 *pDevice, 
    UINT *pReset, 
    IDirect3DDeviceManager9 **ppManager
    )
{
    UINT resetToken = 0;

    IDirect3DDeviceManager9 *pD3DManager = NULL;

    HRESULT hr = DXVA2CreateDirect3DDeviceManager9(&resetToken, &pD3DManager);

    if (FAILED(hr))
    {
        goto done;
    }

    hr = pD3DManager->ResetDevice(pDevice, resetToken);

    if (FAILED(hr))
    {
        goto done;
    }

    *ppManager = pD3DManager;
    (*ppManager)->AddRef();

    *pReset = resetToken;


done:
    SafeRelease(&pD3DManager);
    return hr;
}


The device owner must provide a way for other objects to get a pointer to the IDirect3DDeviceManager9 interface. The standard mechanism is to implement the IMFGetService interface. The service GUID is MR_VIDEO_ACCELERATION_SERVICE.

To share the device among several objects, each object (including the owner of the device) must access the device through the device manager, as follows:

  1. Call IDirect3DDeviceManager9::OpenDeviceHandle to get a handle to the device.
  2. To use the device, call IDirect3DDeviceManager9::LockDevice and pass in the device handle. The method returns a pointer to the IDirect3DDevice9 interface. The method can be called in a blocking mode or a non-blocking mode, depending on the value of the fBlock parameter.
  3. When you are done using the device, call IDirect3DDeviceManager9::UnlockDevice. This method makes the device available to other objects.
  4. Before exiting, call IDirect3DDeviceManager9::CloseDeviceHandle to close the device handle.

You should hold the device lock only while using the device, because holding the device lock prevents other objects from using the device.

The owner of the device can switch to another device at any time by calling ResetDevice, typically because the original device was lost. Device loss can occur for various reasons, including changes in the monitor resolution, power management actions, locking and unlocking the computer, and so forth. For more information, see the Direct3D documentation.

The ResetDevice method invalidates any device handles that were opened previously. When a device handle is invalid, the LockDevice method returns DXVA2_E_NEW_VIDEO_DEVICE. If this occurs, close the handle and call OpenDeviceHandle again to obtain a new device handle, as shown in the following code.

The following example shows how to open a device handle and lock the device.


HRESULT LockDevice(
    IDirect3DDeviceManager9 *pDeviceManager,
    BOOL fBlock,
    IDirect3DDevice9 **ppDevice, // Receives a pointer to the device.
    HANDLE *pHandle              // Receives a device handle.   
    )
{
    *pHandle = NULL;
    *ppDevice = NULL;

    HANDLE hDevice = 0;

    HRESULT hr = pDeviceManager->OpenDeviceHandle(&hDevice);

    if (SUCCEEDED(hr))
    {
        hr = pDeviceManager->LockDevice(hDevice, ppDevice, fBlock);
    }

    if (hr == DXVA2_E_NEW_VIDEO_DEVICE)
    {
        // Invalid device handle. Try to open a new device handle.
        hr = pDeviceManager->CloseDeviceHandle(hDevice);

        if (SUCCEEDED(hr))
        {
            hr = pDeviceManager->OpenDeviceHandle(&hDevice);
        }

        // Try to lock the device again.
        if (SUCCEEDED(hr))
        {
            hr = pDeviceManager->LockDevice(hDevice, ppDevice, TRUE); 
        }
    }

    if (SUCCEEDED(hr))
    {
        *pHandle = hDevice;
    }
    return hr;
}


Related topics

DirectX Video Acceleration 2.0

 

 

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