支持呈现配置文件

音频或视频设备可能支持特定的呈现配置文件。 例如，音频流式处理设备可以通过多个通道以特定比特率流式传输特定类型的内容。 内容类型、流式处理比特率和通道计数称为 呈现配置文件。

WPD 应用程序通常会从驱动程序检索呈现配置文件。 有关应用程序如何检索呈现配置文件的详细信息，请参阅 WPD SDK 中的 检索设备支持的呈现功能 主题。

本主题介绍 WpdWudfSampleDriver 驱动程序如何在 Helpers.cpp 模块中实现对音频流式处理的支持。

当应用程序请求呈现配置文件时，驱动程序会收到WPD_COMMAND_OBJECT_PROPERTIES_GET命令，命令类别为 WPD_CATEGORY_OBJECT_PROPERTIES，WPD_PROPERTY_OBJECT_PROPERTIES_OBJECT_ID为 RenderingInformation。 在示例驱动程序中，收到此命令会触发对 Helpers.cpp 模块中的 SetRenderingProfile 函数的调用。

HRESULT SetRenderingProfiles(
    IPortableDeviceValues*          pValues)
{
    HRESULT hr = S_OK;
    CComPtr<IPortableDeviceValues> pPreferredProfile;
    CComPtr<IPortableDeviceValues> pProfile2;

    CComPtr<IPortableDeviceValuesCollection> pProfiles;

    if(pValues == NULL)
    {
        hr = E_POINTER;
        CHECK_HR(hr, ("Cannot have NULL parameter"));
        return hr;
    }

    // Create the collection to hold the profiles
    if (hr == S_OK)
    {
        hr = CoCreateInstance(CLSID_PortableDeviceValuesCollection,
                              NULL,
                              CLSCTX_INPROC_SERVER,
                              IID_IPortableDeviceValuesCollection,
                              (VOID**) &pProfiles);
        CHECK_HR(hr, "Failed to CoCreateInstance CLSID_PortableDeviceValuesCollection");
    }

    // Get the preferred audio profile
    if (hr == S_OK)
    {
        hr = GetPreferredAudioProfile(&pPreferredProfile);
        CHECK_HR(hr, "Failed to get preferred audio profile properties");
    }

    // Add the profile
    if (hr == S_OK)
    {
        hr = pProfiles->Add(pPreferredProfile);
        CHECK_HR(hr, "Failed to add preferred audio profile to profile collection");
    }

    // Get the second audio profile
    if (hr == S_OK)
    {
        hr = GetAudioProfile2(&pProfile2);
        CHECK_HR(hr, "Failed to get second audio profile properties");
    }

    // Add the profile
    if (hr == S_OK)
    {
        hr = pProfiles->Add(pProfile2);
        CHECK_HR(hr, "Failed to add second audio profile to profile collection");
    }

    // Set the WPD_RENDERING_INFORMATION_PROFILES
    if (hr == S_OK)
    {
        hr = pValues->SetIPortableDeviceValuesCollectionValue(WPD_RENDERING_INFORMATION_PROFILES, pProfiles);
        CHECK_HR(hr, "Failed to set WPD_RENDERING_INFORMATION_PROFILES");
    }

    return hr;
}

而 SetRenderingProfiles 函数又调用 GetPreferredAudioProfile 帮助程序函数，该函数返回 IPortableDeviceValues 对象中的实际配置文件信息。

HRESULT GetPreferredAudioProfile(
    IPortableDeviceValues** ppProfile)
{
    HRESULT hr = S_OK;
    CComPtr<IPortableDeviceValues> pProfile;

    if(ppProfile == NULL)
    {
        hr = E_POINTER;
        CHECK_HR(hr, ("Cannot have NULL parameter"));
        return hr;
    }

    if (hr == S_OK)
    {
        hr = CoCreateInstance(CLSID_PortableDeviceValues,
                              NULL,
                              CLSCTX_INPROC_SERVER,
                              IID_IPortableDeviceValues,
                              (VOID**) &pProfile);
        CHECK_HR(hr, "Failed to CoCreateInstance CLSID_PortableDeviceValues");
    }

    // Set the value for WPD_OBJECT_FORMAT to indicate this profile applies to WMA objects
    if (hr == S_OK)
    {
        hr = pProfile->SetGuidValue(WPD_OBJECT_FORMAT, WPD_OBJECT_FORMAT_WMA);
        CHECK_HR(hr, "Failed to set WPD_OBJECT_FORMAT");
    }

    // Set the preferred value for WPD_MEDIA_TOTAL_BITRATE
    if (hr == S_OK)
    {
        hr = pProfile->SetUnsignedIntegerValue(WPD_MEDIA_TOTAL_BITRATE, 192000);
        CHECK_HR(hr, "Failed to set WPD_MEDIA_TOTAL_BITRATE");
    }

    // Set the preferred value for WPD_AUDIO_CHANNEL_COUNT
    if (hr == S_OK)
    {
        hr = pProfile->SetUnsignedIntegerValue(WPD_AUDIO_CHANNEL_COUNT, 2);
        CHECK_HR(hr, "Failed to set WPD_AUDIO_CHANNEL_COUNT");
    }

    // Set the preferred value for WPD_AUDIO_FORMAT_CODE
    if (hr == S_OK)
    {
        hr = pProfile->SetUnsignedIntegerValue(WPD_AUDIO_FORMAT_CODE, WAVE_FORMAT_MSAUDIO3);
        CHECK_HR(hr, "Failed to set WPD_AUDIO_FORMAT_CODE");
    }

    // Set the output result
    if (hr == S_OK)
    {
        hr = pProfile->QueryInterface(IID_PPV_ARGS(ppProfile));
        CHECK_HR(hr, "Failed to QI for IPortableDeviceValues");
    }

    return hr;
}