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Nick Haddad · Guest

Using the WMFSDK, I am attempting to add a custom DRM property to a WM
file as I am DRMing it. After writing calling
IWMDRMWriter::SetDRMAttribute on all the required properties and
attributes I do the following:

hr = pDrmWriter->SetDRMAttribute( wStreamID,
pwszName,
WMT_TYPE_STRING,
reinterpret_cast<const BYTE*>(pwszMyCustomAttrib),
wszBytes( pwszMyCustomAttrib ) ) );

The value of pwszMyCustomAttrib is L"DRMHeader.MyTest".

The call to SetDRMAttribute is successful return S_OK;

However, when reading this DRM'd file into my client app (which also
uses the WMFSDK, or when reading it using the DRMShow sample
application, IWMDRMReader::GetDRMProperty returns
NS_E_DRM_UNSUPPORTED_PROPERTY (0xC00D275D).

Is there something I am doing wrong here in either the reading or the
writing of this property?

The MSDN docs state (in the article Protecting Files with DRM Version 7) :
"You can add any additional property you wish, such as
'DRMHeader.RequireSAP' for example, as a way of communicating additional
information"

Is there an extra step I need here to define my custom property?

Is it possible that these custom properties are only available after
license aquisition?

Thanks in advance for any help you can provide.

-Nick Haddad

HongJia[MSFT] · Guest

The prefix string "DRMHeader." is not needed when you write the customized
DRM property. And it is required when Reader read the property. In your
case, just write the "MyTest" when you write the property and read the
property using "DRMHeader.MyTest".

In WMFSDK, IWMDRMWriter->SetDRMAttribute automatically adds the "DRMHeader."
to your costomized DRM Property, while IWMDRMReader_GetDRMProperty doesn't.
In your code, it actually adds the DRM Property as
DRMHeader.DRMHeader.MyTest. The property name is not matched when you try to
read it.

Nick Haddad · Guest

HongJia,

Thanks so much for your time, your answer was very helpful!

I have one more questions.

Are any custom attributes I define included in the DRMHeader's digital
signature? I've noticed that you can modify the ContentID (an Optional
attribute) using a hex editor and still play the file fine in WMP.

Thanks for youre help?

-Nick

HongJia[MSFT] · Guest

No problem, you are welcome!

All the DRMHeader attributes including cusotmized attributes are included in
the DRMHeader's digital signature if your DRM content is protected by WMRM
7. Your license server should check the client's header signature in this
case.

Thanks
-HongJia

asdfbmw · Joined: 23 Jun 2006 Posts: 3

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