OpenCV指定pid和vid通过MSMF打开摄像头

在基于OpenCV的项目中，实际开发过程会面临设备上存在多个摄像头，需要指定摄像头的pid和vid打开摄像头。在OpenCV通过MSMF打开摄像头时，需要传入摄像头的index，因此需要在打开该摄像头前需要找出摄像头的index，下面给出通过微软的MF API找出MSMF枚举摄像头index的代码：

#include <windows.h>
#include <mfapi.h>
#include <mfidl.h>
#include <mfreadwrite.h>
#include <string>
#include <vector>
#include <iostream>
#include <opencv2/opencv.hpp>

#pragma comment(lib, "mf.lib")
#pragma comment(lib, "mfplat.lib")
#pragma comment(lib, "mfreadwrite.lib")
#pragma comment(lib, "mfuuid.lib")

struct CameraInfo {
    int index;      // OpenCV 摄像头索引
    int vid;        // Vendor ID (e.g., 0x046D for Logitech)
    int pid;        // Product ID (e.g., 0x0825 for C920)
    std::string symbolicLink; // 设备符号链接
};

// 获取所有 Media Foundation 摄像头的 PID/VID
std::vector<CameraInfo> getMFCameraList() {
    std::vector<CameraInfo> cameras;

    IMFAttributes* pAttributes = nullptr;
    IMFActivate** ppDevices = nullptr;
    UINT32 count = 0;

    // 初始化 Media Foundation
    MFStartup(MF_VERSION);

    // 配置设备枚举参数（仅视频采集设备）
    MFCreateAttributes(&pAttributes, 1);
    pAttributes->SetGUID(
        MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE,
        MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_GUID
    );

    // 枚举设备
    MFEnumDeviceSources(pAttributes, &ppDevices, &count);

    for (UINT32 i = 0; i < count; i++) {
        WCHAR* symbolicLink = nullptr;
        UINT32 length = 0;

        // 获取设备 Symbolic Link（包含 VID/PID）
        ppDevices[i]->GetAllocatedString(
            MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_SYMBOLIC_LINK,
            &symbolicLink,
            &length
        );

        if (symbolicLink) {
            std::wstring ws(symbolicLink);
            std::string devicePath(ws.begin(), ws.end());

            // 解析 VID/PID（格式：\\?\usb#vid_xxxx&pid_xxxx...）
            size_t vidPos = devicePath.find("vid_");
            size_t pidPos = devicePath.find("pid_");

            if (vidPos != std::string::npos && pidPos != std::string::npos) {
                std::string vidStr = devicePath.substr(vidPos + 4, 4);
                std::string pidStr = devicePath.substr(pidPos + 4, 4);

                int vid = std::stoi(vidStr, nullptr, 16);
                int pid = std::stoi(pidStr, nullptr, 16);

                cameras.push_back({-1, vid, pid, devicePath});
            }

            CoTaskMemFree(symbolicLink);
        }
        ppDevices[i]->Release();
    }

    if (pAttributes) pAttributes->Release();
    if (ppDevices) CoTaskMemFree(ppDevices);
    MFShutdown();

    return cameras;
}

// 匹配 OpenCV 摄像头索引
int findOpenCVCameraIndex(int targetVid, int targetPid) {
    auto cameras = getMFCameraList();
    int opencvIndex = 0;

    while (true) {
        cv::VideoCapture cap(opencvIndex, cv::CAP_MSMF);
        if (!cap.isOpened()) {
            break; // 没有更多摄像头
        }

        // 检查当前摄像头是否匹配目标 PID/VID
        for (const auto& cam : cameras) {
            if (cam.vid == targetVid && cam.pid == targetPid) {
                std::cout << "Found camera at OpenCV index: " << opencvIndex << std::endl;
                cap.release();
                return opencvIndex;
            }
        }

        cap.release();
        opencvIndex++;
    }

    return -1; // 未找到
}

int main() {
    // 示例：查找 Logitech C920（VID=0x046D, PID=0x0825）
    int targetVid = 0x046D;
    int targetPid = 0x0825;

    int cameraIndex = findOpenCVCameraIndex(targetVid, targetPid);
    if (cameraIndex != -1) {
        cv::VideoCapture cap(cameraIndex, cv::CAP_MSMF);
        if (cap.isOpened()) {
            std::cout << "Successfully opened target camera!" << std::endl;
            // 进行视频捕获...
        }
    } else {
        std::cerr << "Target camera not found." << std::endl;
    }

    return 0;
}