设置文件的元数据

项目
06/13/2023

在使用 IWMDMStorageControl3：：Insert3 () 或在现有存储 (上调用 IWMDMStorage3：：SetMetadata) 时，可以在文件写入设备之前设置元数据。通过调用 IWMDMStorage：：SetAttributes 或 IWMDMStorage2：：SetAttributes2) ，只能在现有存储 (上设置属性。

通过创建并填充传递到 IWMDMStorageControl3：：Insert3 的 IWMDMMetaData 接口来完成元数据设置。但是，此方法可以清除文件上的所有现有元数据，但文件系统本身中存储的硬编码元数据（如文件名或大小）不一样。因此，必须将要保留的所有现有元数据复制到提交的 IWMDMMetaData 接口中。由于 Windows Media 设备管理器不能用于从本地文件检索元数据，因此必须使用 Windows Media Format SDK (或其他一些工具) 检索此类元数据。

若要使用 Windows Media Format SDK 检索 ASF 文件属性，请执行以下步骤：

通过调用 WMCreateEditor 并请求 IWMMetadataEditor 接口创建元数据编辑器对象。
通过调用 IWMMetadataEditor：：Open 打开文件以读取元数据。
如果文件是有效的 ASF 文件并且可以打开，请在编辑器中查询 IWMHeaderInfo 接口。
通过调用 IWMHeaderInfo：：GetAttributeByName 并传入所需的 Windows Media Format SDK 属性常量来检索文件属性。下表提供了具有等效 Windows Media 设备管理器 SDK 常量的格式 SDK 常量列表。

Windows Media Format SDK 常量	Windows Media 设备管理器 SDK 常量
g_wszWMTitle	g_wszWMDMTitle
g_wszWMAuthor	g_wszWMDMAuthor
g_wszWMAlbumTitle	g_wszWMDMAlbumTitle
g_wszWMGenre	g_wszWMDMGenre
g_wszWMYear	g_wszWMDMYear
g_wszWMTrackNumber或g_wszWMTrack	g_wszWMDMTrack
g_wszWMComposer	g_wszWMDMComposer
g_wszWMDuration	g_wszWMDMDuration
g_wszWMCopyright	g_wszWMDMProviderCopyright
g_wszWMDescription	g_wszWMDMDescription
g_wszWMBitrate	g_wszWMDMBitrate
g_wszWMRating	g_wszWMDMUserRating
g_wszWMAlbumArtist	g_wszWMDMAlbumArtist
g_wszWMParentalRating	g_wszWMDMParentalRating
g_wszWMRadioStationName	g_wszWMDMMediaStationName
g_wszWMSubTitle	g_wszWMDMSubTitle
g_wszWMVideoWidth	g_wszWMDMWidth
g_wszWMVideoHeight	g_wszWMDMHeight
g_wszWMMood	g_wszWMDMTrackMood
g_wszWMCodec	g_wszAudioWAVECodec或g_wszVideoFourCCCodec

以下 C++ 示例代码演示如何使用 Windows Media Format SDK 从 ASF 文件检索大量元数据属性，并将其转换为等效的 Windows Media 设备管理器值。

// Structure and array to hold equivalent Windows Media Format SDK 
// and Windows Media Device Manager SDK metadata property names.
struct EquivalentProperty
{
    LPCWSTR FormatSDKConst;
    LPCWSTR WMDMSDKConst;
};
EquivalentProperty EquivalentProperties []= 
{
    {g_wszWMTitle,        g_wszWMDMTitle},
    {g_wszWMAuthor,      g_wszWMDMAuthor},
    {g_wszWMAlbumTitle,  g_wszWMDMAlbumTitle},
    {g_wszWMGenre,       g_wszWMDMGenre},
    {g_wszWMYear,        g_wszWMDMYear},
    {g_wszWMTrackNumber, g_wszWMDMTrack},
    {g_wszWMTrack,       g_wszWMDMTrack},
    {g_wszWMComposer,    g_wszWMDMComposer},
    {g_wszWMBitrate,     g_wszWMDMBitrate},
    {g_wszWMDuration,    g_wszWMDMDuration},
    {g_wszWMCopyright,   g_wszWMDMProviderCopyright},
    {g_wszWMDescription, g_wszWMDMDescription},
    {g_wszWMRating,      g_wszWMDMUserRating},
    {g_wszWMAlbumArtist, g_wszWMDMAlbumArtist},
    {g_wszWMParentalRating,    g_wszWMDMParentalRating},
    {g_wszWMRadioStationName,  g_wszWMDMMediaStationName},
    {g_wszWMSubTitle,    g_wszWMDMSubTitle},
    {g_wszWMVideoWidth,  g_wszWMDMWidth},
    {g_wszWMVideoHeight, g_wszWMDMHeight},
    {g_wszWMMood,        g_wszWMDMTrackMood},
    {g_wszWMCodec,       g_wszAudioWAVECodec},
    {g_wszWMCodec,       g_wszVideoFourCCCodec}
};
// Function that tries to get metadata by using the Format SDK. 
// If it cannot open the file, it returns E_FAIL.
HRESULT GetFileMetadataFromFormatSDK(IWMDMMetaData* pMetadata, LPCWSTR file)
{
    if ((pMetaData == NULL) || (file == NULL)) return E_INVALIDPARAM;
    HRESULT hr = S_OK;
    CComPtr<IWMMetadataEditor> pEditor;

    // Do loop to allow easy error trapping. Even if there are no errors, 
    // the loop executes only once.
    do {
        hr = WMCreateEditor(&pEditor);
        if (FAILED(hr)) 
            break;

        // Open the file.
        hr = pEditor->Open(file);
        if (FAILED(hr)) 
            break;

        CComPtr<IWMHeaderInfo>pHeaderInfo;
        hr = pEditor->QueryInterface(__uuidof(IWMHeaderInfo), (void**)&pHeaderInfo);
        if (FAILED(hr))
            break;

        // Copy values from Format SDK to equivalent WMDM SDK metadata values.

        // Loop through all known values
        WORD stream = 0;
        WMT_ATTR_DATATYPE wmfType;
        WORD len = 0;
        BYTE* value = NULL;
        WMDM_TAG_DATATYPE wmdmType;
        for (int i = 0; i < sizeof(EquivalentProperties) / sizeof(EquivalentProperties[0]); i++)
        {
            // Request each value from our equivalency list by name.
            // The function is called twice: once to get the buffer size,
            // and once to get the value in the allocated buffer.
            if (FAILED(pHeaderInfo->GetAttributeByName(
                &stream, EquivalentProperties[i].FormatSDKConst, &wmfType, NULL, &len)))
            {
                continue;
            }

            value = new BYTE[len];
            if (value == NULL) continue;

            if (FAILED(pHeaderInfo->GetAttributeByName(&stream, EquivalentProperties[i].FormatSDKConst, &wmfType, value, &len)))
            {
                delete[] value;
                continue;
            }

            // Send the data to the equivalent WMDM metadata value.
            // First, find the equivalent WMDM type for the WMF type.
            switch(wmfType)
            {
            case WMT_TYPE_BINARY:
                wmdmType = WMDM_TYPE_BINARY;
                break;
            case WMT_TYPE_DWORD:
                wmdmType = WMDM_TYPE_DWORD;
                break;
            case WMT_TYPE_STRING:
                wmdmType = WMDM_TYPE_STRING;
                break;
            case WMT_TYPE_BOOL:
                wmdmType = WMDM_TYPE_BOOL;
                break;
            case WMT_TYPE_QWORD:
                wmdmType = WMDM_TYPE_QWORD;
                break;
            case WMT_TYPE_WORD:
                wmdmType = WMDM_TYPE_WORD;
                break;
            case WMT_TYPE_GUID:
                wmdmType = WMDM_TYPE_GUID;
                break;
            default:
                wmdmType = WMDM_TYPE_BINARY;
                break;
            }

            // Don't worry about trapping errors, because there's nothing 
            // we can do about it.
            pMetadata->AddItem(wmdmType, 
                EquivalentProperties[i].WMDMSDKConst, value, len);
            delete[] value;
        } // Add next value.
    } while (FALSE); // End Do loop error trap.

    // Close the file opened with IWMMetadataEditor.
    pEditor->Close();
    return hr;
}

以下 C++ 示例函数演示如何使用 DirectShow 获取一些文件信息并将其添加到元数据中。

// For IMediaDet, you must link to strmiids.lib. Also include the following:
//#include <Qedit.h>  // for IMediaDet declaration.
//#include <Dshow.h>  // for VIDEOINFOHEADER declaration.
HRESULT GetFileMetadataFromDShow(IWMDMMetaData* pMetadata, LPCWSTR file)
{
    HRESULT hr = S_OK;

    // Add file metadata properties from DirectShow. 
    // This is good for non-ASF files, or to add any information
    // that the Format SDK didn't get.

    // Do loop to allow easy error trapping. Even if there are no errors, 
    // the loop executes only once.
    do
    {
        // Create the Media Detector object.
        CComPtr<IMediaDet> pIMediaDet;
        hr = pIMediaDet.CoCreateInstance(CLSID_MediaDet, NULL);
        if (FAILED(hr)) 
            break;

        // Open the file.
        hr = pIMediaDet->put_Filename(BSTR(file));
        if (FAILED(hr))
            break;

        // Get the media type for the default stream.
        AM_MEDIA_TYPE mediaType;
        hr = pIMediaDet->get_StreamMediaType(&mediaType);
        if (FAILED(hr))
            break;

        // We have the file open, so start requesting information from the 
        // Media Detector and adding it to the metadata. When adding 
        // individual metadata values, ignore the HRESULT, because failure 
        // to add these metadata values is not a breaking issue.

        // Get major and minor types.
        WCHAR strMediaType[64];
        ZeroMemory(strMediaType, 64);

        //Change the major type to a string, then add to IWMDMMetaData.
        StringFromGUID2(reinterpret_cast<GUID&>(mediaType.majortype),
            (LPOLESTR)strMediaType, 64);
        hr = pMetadata->AddItem(WMDM_TYPE_STRING, 
             g_wszWMDMediaClassPrimaryID, 
            (BYTE*) strMediaType, 
             sizeof(strMediaType) / sizeof(strMediaType[0]));

        // Clear local string, then retrieve subtype the same way.
        ZeroMemory(strMediaType, 64);
        StringFromGUID2(reinterpret_cast<GUID&>(mediaType.subtype),
            (LPOLESTR)strMediaType, 64);
        hr = pMetadata->AddItem(WMDM_TYPE_STRING, 
            g_wszWMDMMediaClassSecondaryID, (BYTE*) strMediaType,
            sizeof(strMediaType) / sizeof(strMediaType[0]));

        // Get the duration. Duration is retrieved in seconds, but set 
        // in 100-nanosecond units.
        double duration = 0;
        hr = pIMediaDet->get_StreamLength(&duration);
        if (duration > 0)
        {
            duration *= 10E7;
            hr = pMetadata->AddItem(WMDM_TYPE_DWORD, g_wszWMDMDuration, (BYTE*) &duration, sizeof(duration));
        }

        // Get the frame rate.
        double frameRate = 0;
        hr = pIMediaDet->get_FrameRate(&frameRate);
        if (frameRate > 0)
        {
            hr = pMetadata->AddItem(WMDM_TYPE_DWORD, g_wszWMDMFrameRate, 
                (BYTE*) &frameRate,
                sizeof(frameRate));
        }

        // Get the structure for the default stream's major type and 
        // fill in additional information.

        if (IsEqualGUID(mediaType.formattype, FORMAT_VideoInfo))
        {
            VIDEOINFOHEADER* data = (VIDEOINFOHEADER*) mediaType.pbFormat;
            hr = pMetadata->AddItem(WMDM_TYPE_DWORD, g_wszWMDMVideoBitrate, 
               (BYTE*) &data->dwBitRate, sizeof(DWORD));
            hr = pMetadata->AddItem(WMDM_TYPE_DWORD, g_wszWMDMHeight, 
               (BYTE*) &data->bmiHeader.biHeight, sizeof(LONG));
            hr = pMetadata->AddItem(WMDM_TYPE_DWORD, g_wszWMDMWidth, 
               (BYTE*) &data->bmiHeader.biWidth, sizeof(LONG));
        }

        if (IsEqualGUID(mediaType.formattype, FORMAT_WaveFormatEx))
        {
            WAVEFORMATEX* data = (WAVEFORMATEX*) mediaType.pbFormat;
            hr = pMetadata->AddItem(WMDM_TYPE_WORD, g_wszWMDMBlockAlignment, 
                (BYTE*) &data->nBlockAlign, sizeof(WORD));
            hr = pMetadata->AddItem(WMDM_TYPE_WORD, g_wszWMDMNumChannels, 
               (BYTE*) &data->nChannels, sizeof(WORD));
        }
    } while (FALSE); // End of error loop.
    return hr;
}

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