New Driver and Application Whitepapers Are Here

wpdblog — Mon, 07 May 2007 21:51:00 GMT

We've published two new WPD developer-centric whitepapers at the Microsoft WHDC website for WinHEC.

The first covers how to do WMDRM metering and license synchronization from a WPD application; the second describes how to port the existing WPD "Hello World" sample driver to communicate with a Parallax Basic Stamp II microcontroller to read temperature sensor data. Both contain sample code.

I. Accessing WMDRM APIs from a WPD Application:

http://www.microsoft.com/whdc/device/media/WMDRM_API.mspx

This whitepaper describes how to associate a WPD device instance with a WMDM device instance for MTP devices; the WMDM device instance is then used for calling Windows Media Digital Rights Management (WMDRM) application interfaces. To build the sample WPD application, you need the Windows Media Format SDK v11 and the Windows SDK (v6000).

II. Creating a WPD Driver for a Microcontroller-Based Sensor:

http://www.microsoft.com/whdc/device/media/WPD_drv.mspx

This sample is based on the Parallax Basic Stamp II microcontroller to provide an example of a simple hardware device that can have a WPD driver for it. Parallax provides an activity kit that contains the hardware components for this sample driver. To build the driver, you need the Windows Driver Kit (v6000).

References

All WPD-related whitepapers are posted here.

More information on downloading the various SDKs.

This posting is provided "AS IS" with no warranties, and confers no rights.

Working with WMDRM Protected Content using WPD

wpdblog — Sat, 10 Feb 2007 02:55:00 GMT

Setting up your WPD application to handle protected WMDRM content

The WPD API supports the transfer and licensing operations for Windows Media Digital Rights Management (WMDRM) content.

This MSDN article describes two additional properties that are required to enable your WPD application to transfer protected content.

Property	Vartype	Description
WPD_CLIENT_WMDRM_APPLICATION_PRIVATE_KEY	VT_VECTOR \| VT_UI1	Specifies the application's private key.
WPD_CLIENT_WMDRM_APPLICATION_CERTIFICATE	VT_VECTOR \| VT_UI1	Specifies the application's certificate.

To initialize WPD for protected content, call IPortableDevice::Open() with the above parameters added to the pClientInfo IPortableDeviceValues. If this succeeds, you can use the derived IPortableDeviceContent interface (from IPortableDevice::Content()) to transfer protected (and clear) content using IPortableDeviceContent::CreateObjectWithPropertiesAndData().

To obtain a private application key and certificate, visit this link.

Transferring Content

To transfer WMDRM protected content, use IPortableDeviceContent::CreateObjectWithPropertiesAndData(). The same CreateObjectWithPropetiesAndData API call can be used for both protected and clear content without additional options. The WPD API will automatically select the protected or clear channel depending on whether the content is protected or clear. It interfaces with the WMDRM Secure Content Provider to process the WMDRM licenses.

Transferring Known Clear Content

If you've enabled WPD to handle protected content, but you know that a specific file is not protected, you can tell WPD to skip the DRM processing by setting WPD_API_OPTION_USE_CLEAR_DATA_STREAM option to TRUE in the input IPortableDeviceValues when calling IPortableDeviceContent::CreateObjectWithPropertiesAndData() for clear content.

Accessing Metering Operations using IWMDRMDeviceApp

WPD provides a mechanism to access the IWMDRMDeviceApp APIs for license updates and metering data retrieval. To access IWMDRMDeviceApp through WPD, call QueryInterface on IID_IWMDRMDeviceApp from the IStream returned from IPortableDeviceContent::CreateObjectWithPropertiesAndData(). This IWMDRMDeviceApp instance tied to the IPortableDevice connection to your WMDRM-compatible device, and not the specific content where the IStream was obtained. WPD internally wraps the metering APIs and makes it accessible to your application. Your application uses a constant for the IWMDMDevice* parameter: WMDRMDEVICEAPP_USE_WPD_DEVICE_PTR.

IStream* pDataStream = NULL;

IWMDRMDeviceApp* pWMDRMApp = NULL;

// ... Initialization

hr = pPortableDeviceContent->CreateObjectWithPropertiesAndData(pValues,

&pDataStream,

&dwOptimalWriteBufferSize,

NULL);

// ... Transfer the protected WMDRM content

pDataStream->Write(pData, cbData, &cbWritten);

pDataStream->Commit(0);

hr = pDataStream->QueryInterface(IID_IWMDRMDeviceApp,

(void**)&pWMDRMApp);

if (SUCCEEDED(hr))

{

DWORD dwStatus = 0;

// Call metering operations on the current device using the WPD device pointer

hr = pWMDRMApp->QueryDeviceStatus((IWMDMDevice *)WMDRMDEVICEAPP_USE_WPD_DEVICE_PTR,

&dwStatus);

}

The same pre-requisitie with the application private key and certificate applies here as well. If the key/certificate is invalid or if the WMDRM system fails to initialize, the QueryInferface call will fail.

Update [March 13, 2007]: The above method to acquire the IWMDRMDeviceApp interface from the IStream pointer is just a convenience if your application is already doing a prior protected content transfer, before proceeding on to do metering and license synchronization operations.

Our recommendation for most applications that need to access IWMDRMDeviceApp is to initialize IWMDRMDeviceApp directly as this does not require your application to transfer protected content or hold on to the transfer interfaces in order to do device metering and license sync. For details, refer to this MSDN article entitled "Handling Protected Content in the Application."

Update [May 5, 2007]: The whitepaper (and sample code) on initializing IWMDRMDeviceApp for WPD is now posted here.

This posting is provided "AS IS" with no warranties, and confers no rights.

Windows Portable Devices Team Blog : DRM

New Driver and Application Whitepapers Are Here

Working with WMDRM Protected Content using WPD