使用多比特率互斥
[与此页面关联的功能 Windows Media Format 11 SDK 是旧版功能。 它已被源读取器和接收器编写器取代。 源读取器和接收器编写器已针对Windows 10和Windows 11进行了优化。 Microsoft 强烈建议新代码尽可能使用源读取器和接收器编写器，而不是 Windows Media Format 11 SDK。 如果可能，Microsoft 建议重写使用旧 API 的现有代码以使用新 API。]
多比特率 (MBR) 互斥在为各种播放方案对内容进行编码时非常有用。 MBR 视频输出由多次编码的单个输入组成，每个输入具有不同的比特率设置。 读取具有 MBR 编码的文件时，读取器将根据可用带宽确定要使用的流。
Windows Media Format SDK 支持视频流和音频流的 MBR 编码。 此外，还可以创建一种特殊类型的 MBR 编码，称为多视频大小的 MBR 编码。 多视频大小的 MBR 视频与普通 MBR 视频的功能相同，只不过可以在相互排除中为视频流指定不同的图像大小。
以下示例演示如何为具有多个视频大小的 MBR 视频设置配置文件。 它创建一个新的配置文件，其中包含三个比特率和大小不同的视频流，并将其包含在互斥对象中。
IWMProfileManager* pProfileMgr = NULL;
IWMProfile* pProfile = NULL;
IWMMutualExclusion* pMutex = NULL;
IWMStreamConfig* pStream = NULL;
IWMMediaProps* pMediaProps = NULL;
WM_MEDIA_TYPE* pMediaType = NULL;
DWORD cbMediaType = 0;
HRESULT hr = S_OK;
// Initialize COM.
hr = CoInitialize(NULL);
// Create a profile manager object.
hr = WMCreateProfileManager(&pProfileMgr);
// Create an empty profile.
hr = pProfileMgr->CreateEmptyProfile(WMT_VER_9_0, &pProfile);
// Give the new profile a name and description.
hr = pProfile->SetName(L"MBR_Video_3_Stream_test");
hr = pProfile->SetDescription(L"Only for use with example code.");
// Create the first stream.
hr = pProfile->CreateNewStream(WMMEDIATYPE_Video, &pStream);
// Get the media properties interface for the new stream.
hr = pStream->QueryInterface(IID_IWMMediaProps, (void**)&pMediaProps);
// Get the media-type structure.
// First, get the size of the media-type structure.
hr = pMediaProps->GetMediaType(NULL, &cbMediaType);
// Allocate memory for the structure based on the retrieved size.
pMediaType = (WM_MEDIA_TYPE*) new BYTE[cbMediaType];
// Retrieve the media-type structure.
hr = pMediaProps->GetMediaType(pMediaType, &cbMediaType);
// Change the video size to 640 x 480.
pMediaType->pbFormat->bmiHeader.biWidth = 640;
pMediaType->pbFormat->bmiHeader.biHeight = 480;
// Replace the WM_MEDIA_TYPE in the profile with the one just changed.
hr = pMediaProps->SetMediaType(pMediaType);
// Release the media properties interface and delete the structure.
pMediaProps->Release();
pMediaProps = NULL;
delete[] pMediaType;
pMediaType = NULL;
// Set the bit rate to 200.
hr = pStream->SetBitrate(200000);
// Set the stream number.
hr = pStream->SetStreamNumber(1);
// Include the new stream in the profile.
hr = pProfile->AddStream(pStream);
// Release the stream configuration interface.
pStream->Release();
pStream = NULL;
// For the remaining two streams, leave the video at its default size of
// 320 x 240 <entity type="ndash"/>- just change the bit rates.
// Repeat for a 100K stream.
hr = pProfile->CreateNewStream(WMMEDIATYPE_Video, &pStream);
hr = pStream->SetBitrate(100000);
hr = pStream->SetStreamNumber(2);
hr = pProfile->AddStream(pStream);
pStream->Release();
pStream = NULL;
// Repeat for a 56K stream.
hr = pProfile->CreateNewStream(WMMEDIATYPE_Video, &pStream);
hr = pStream->SetBitrate(56000);
hr = pStream->SetStreamNumber(3);
hr = pProfile->AddStream(pStream);
pStream->Release();
pStream = NULL;
// Now that we have three streams, create a mutual exclusion object.
hr = pProfile->CreateNewMutualExclusion(&pMutex);
// Add the three streams to the mutual exclusion.
hr = pMutex->AddStream(1);
hr = pMutex->AddStream(2);
hr = pMutex->AddStream(3);
// Configure the mutual exclusion for MBR video.
hr = pMutex->SetType(CLSID_WMMUTEX_Bitrate);
// Add the mutual exclusion to the profile.
hr = pProfile->AddMutualExclusion(pMutex);
// Release the mutual exclusion object.
pMutex->Release();
pMutex = NULL;
// TODO: Save the profile to a string, and save the string to a file.
// For more information, see To Save a Custom Profile.
// Release remaining interfaces.
pProfile->Release();
pProfile = NULL;
pProfileMgr->Release();
pProfileMgr = NULL;
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