DirectShow设置摄像头分辨率和图像格式

DirectShow设置摄像头的分辨率和图像格式代码如下所示：

// 设置参数，width=宽，height=高，fps=帧率
AM_MEDIA_TYPE *p = NULL;
IAMStreamConfig *pSC = NULL;
pCGB2->FindInterface(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video, pVCap, 
    IID_IAMStreamConfig, (void **)&pSC);
pSC->GetFormat(&p);
VIDEOINFOHEADER *pHd = (VIDEOINFOHEADER *)p->pbFormat;
// 单位为100ns，所以每帧(10^7/fps)*100ns
pHd->AvgTimePerFrame = 10000000 / fps;
// I420格式
pHd->bmiHeader.biCompression = MAKEFOURCC('I', '4', '2', '0');
pHd->bmiHeader.biWidth = width;
pHd->bmiHeader.biHeight = height;
// 一个像素点12位
pHd->bmiHeader.biBitCount = 12;
// 图像大小
pHd->bmiHeader.biSizeImage = width * height * 3 / 2;
// 图像传输率，单位bps
pHd->dwBitRate = pHd->bmiHeader.biSizeImage * 8 * fps;
// defined in wmsdkidl.h
p->subtype = WMMEDIASUBTYPE_I420;
p->lSampleSize = pHd->bmiHeader.biSizeImage;
pSC->SetFormat(p);
// free p
FreeAM_MEDIA_TYPE(p);
pSC->Release();

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