Shell Metadata Providers

Starting in Windows 7, Microsoft Media Foundation exposes metadata through the IPropertyStore interface.

Metadata obtained using the process defined in this topic should only be used for read-only access. Writing data using this process is not supported. You can create an IPropertyStore object for writing purposes using a class identifier (CLSID) obtained from PSLookupPropertyHandlerCLSID.

Reading Metadata

To read metadata from a media source, perform the following steps:

  1. Get a pointer to the IMFMediaSource interface of the media source. You can use the IMFSourceResolver interface to get an IMFMediaSource pointer.
  2. Call MFGetService on the media source to get a pointer to the IPropertyStore interface. In the guidService parameter of MFGetService, specify the value MF_PROPERTY_HANDLER_SERVICE. If the source does not support the IPropertyStore interface, MFGetService returns MF_E_UNSUPPORTED_SERVICE.
  3. Call IPropertyStore methods to enumerate the metadata properties.

The following code shows these steps. Assume that DisplayProperty is a function that displays a PROPVARIANT value.


HRESULT EnumerateMetadata(IMFMediaSource *pSource)
{
    IPropertyStore *pProps = NULL;

    HRESULT hr = MFGetService(
        pSource, MF_PROPERTY_HANDLER_SERVICE, IID_PPV_ARGS(&pProps));

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

    DWORD cProps;

    hr = pProps->GetCount(&cProps);
    if (FAILED(hr))
    {
        goto done;
    }

    for (DWORD i = 0; i < cProps; i++)
    {
        PROPERTYKEY key;
        hr = pProps->GetAt(i, &key);
        if (FAILED(hr))
        {
            goto done;
        }

        PROPVARIANT pv;

        hr = pProps->GetValue(key, &pv);
        if (FAILED(hr))
        {
            goto done;
        }

        DisplayProperty(key, pv);
        PropVariantClear(&pv);
    }

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


For a list of metadata property keys, see Metadata Properties for Media Files.

Related topics

Media Metadata

 

 

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