Partager via

Determining Playlist Synchronization State

  • Article

[The feature associated with this page, Windows Media Player SDK, is a legacy feature. It has been superseded by MediaPlayer. MediaPlayer has been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer instead of Windows Media Player SDK, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

Windows Media Player 10 or later uses the SyncState attribute to contain information about whether a particular digital media file has been copied to a portable device and, in the case of a failure, whether copying failed because the device did not have enough memory.

The following example code creates a function that retrieves this information from a digital media file. The function takes the following parameters:

  • pMedia. Pointer to an IWMPMedia interface that represents the digital media file to inspect.
  • lPsIndex. Partnership index of the current device.
  • pulOnDevice. Pointer to a long variable that receives the value indicating whether the digital media file has been copied to the device.
  • pulDidNotFit. Pointer to a long variable that receives the value indicating whether the copy operation failed because the device did not have enough memory.

The information contained in the SyncState attribute is encoded in a bitwise fashion. You can see how this function is used in the example code in Enumerating the Media Items.

STDMETHODIMP CSyncSettings::GetPartnershipSyncState(IWMPMedia* pMedia, long lPsIndex, ULONG *pulOnDevice, ULONG *pulDidNotFit)
{
    ATLASSERT(pMedia); 
    ATLASSERT(lPsIndex > 0 && 
              lPsIndex < 17);
    ATLASSERT(pulOnDevice);
    ATLASSERT(pulDidNotFit);
  
    CComVariant varSyncStateVal;   
    CComPtr<IWMPMedia> spMedia(pMedia); 
    CComPtr<IWMPMedia3> spMedia3;     
    HRESULT hr = spMedia.QueryInterface(&spMedia3); 
    ULONG ulSyncState = 0; // Stores the ulVal member of varSyncStateVal. 
    ULONG lLSB = 0; // Represents least significant bit: Did the media fail to copy because it would not fit?
    ULONG lMSB = 0; // Represents most significant bit: Is the media on the device?

    // Calculate the bit shift required to isolate the partnership bit 
    // pair from the SyncState attribute.
    const int iRshift = (lPsIndex - 1) * 2;

    if(SUCCEEDED(hr) && spMedia3)
    {       
        hr = spMedia3->getItemInfoByType(CComBSTR("SyncState"), CComBSTR(""), 0, &varSyncStateVal);
    }

    if(SUCCEEDED(hr) && varSyncStateVal.vt == VT_UI4)
    {   
        // Get the value.
        ulSyncState = varSyncStateVal.ulVal;

        // Shift the bit pair to the rightmost position.
        ulSyncState >>= iRshift; 

        // Mask the rightmost bit pair.
        ulSyncState &= 3;

        // Get the LSB         
        lLSB = ulSyncState & ~2; // Sets the 2E1 bit to zero. 

        // Get the MSB
        ulSyncState >>= 1;
        lMSB = ulSyncState;       
    }

    // Return the bits.
    *pulOnDevice = lMSB;
    *pulDidNotFit = lLSB;

    return hr;
}

IWMPMedia Interface

IWMPMedia3::getItemInfoByType

Managing Synchronization Playlists

SyncState Attribute