【发布时间】：2020-01-23 12:19:03
【问题描述】：
当使用Source Reader 时，我可以使用它来获取解码后的 YUV 样本，使用 mp4 文件源 (example code)。
如何使用网络摄像头源做相反的事情？使用 Source Reader 提供编码的 H264 样本？我的网络摄像头支持 RGB24 和 I420 像素格式，如果我手动连接 H264 MFT 变换，我可以获得 H264 样本。但似乎源阅读器应该能够为我处理转换。每当我尝试在 Source Reader 上设置 MF_MT_SUBTYPE 或 MFVideoFormat_H264 时都会出错。
示例 sn-p 如下所示，完整示例为 here。
// Get the first available webcam.
CHECK_HR(MFCreateAttributes(&videoConfig, 1), "Error creating video configuration.");
// Request video capture devices.
CHECK_HR(videoConfig->SetGUID(
MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE,
MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_GUID), "Error initialising video configuration object.");
CHECK_HR(videoConfig->SetGUID(MF_MT_SUBTYPE, WMMEDIASUBTYPE_I420),
"Failed to set video sub type to I420.");
CHECK_HR(MFEnumDeviceSources(videoConfig, &videoDevices, &videoDeviceCount), "Error enumerating video devices.");
CHECK_HR(videoDevices[WEBCAM_DEVICE_INDEX]->GetAllocatedString(MF_DEVSOURCE_ATTRIBUTE_FRIENDLY_NAME, &webcamFriendlyName, &nameLength),
"Error retrieving video device friendly name.\n");
wprintf(L"First available webcam: %s\n", webcamFriendlyName);
CHECK_HR(videoDevices[WEBCAM_DEVICE_INDEX]->ActivateObject(IID_PPV_ARGS(&pVideoSource)),
"Error activating video device.");
CHECK_HR(MFCreateAttributes(&pAttributes, 1),
"Failed to create attributes.");
// Adding this attribute creates a video source reader that will handle
// colour conversion and avoid the need to manually convert between RGB24 and RGB32 etc.
CHECK_HR(pAttributes->SetUINT32(MF_SOURCE_READER_ENABLE_VIDEO_PROCESSING, 1),
"Failed to set enable video processing attribute.");
CHECK_HR(pAttributes->SetGUID(MF_MT_MAJOR_TYPE, MFMediaType_Video), "Failed to set major video type.");
// Create a source reader.
CHECK_HR(MFCreateSourceReaderFromMediaSource(
pVideoSource,
pAttributes,
&pVideoReader), "Error creating video source reader.");
MFCreateMediaType(&pSrcOutMediaType);
CHECK_HR(pSrcOutMediaType->SetGUID(MF_MT_MAJOR_TYPE, MFMediaType_Video), "Failed to set major video type.");
CHECK_HR(pSrcOutMediaType->SetGUID(MF_MT_SUBTYPE, MFVideoFormat_H264), "Error setting video sub type.");
CHECK_HR(pSrcOutMediaType->SetUINT32(MF_MT_AVG_BITRATE, 240000), "Error setting average bit rate.");
CHECK_HR(pSrcOutMediaType->SetUINT32(MF_MT_INTERLACE_MODE, 2), "Error setting interlace mode.");
CHECK_HR(pVideoReader->SetCurrentMediaType((DWORD)MF_SOURCE_READER_FIRST_VIDEO_STREAM, NULL, pSrcOutMediaType),
"Failed to set media type on source reader.");
CHECK_HR(pVideoReader->GetCurrentMediaType((DWORD)MF_SOURCE_READER_FIRST_VIDEO_STREAM, &pFirstOutputType),
"Error retrieving current media type from first video stream.");
std::cout << "Source reader output media type: " << GetMediaTypeDescription(pFirstOutputType) << std::endl << std::endl;
输出：
bind returned success
First available webcam: Logitech QuickCam Pro 9000
Failed to set media type on source reader. Error: C00D5212.
finished.
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