shm-demo/sender.cpp

#include <iostream>
#include <opencv2/opencv.hpp>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>

int main() {
    // 打开视频文件
    cv::VideoCapture cap("1.mp4");
    if (!cap.isOpened()) {
        std::cerr << "Failed to open video file" << std::endl;
        return 1;
    }

    // 获取视频帧率
    double fps = cap.get(cv::CAP_PROP_FPS);
    std::cout << "Original FPS: " << fps << std::endl;

    // 获取图像尺寸
    int width = cap.get(cv::CAP_PROP_FRAME_WIDTH);
    int height = cap.get(cv::CAP_PROP_FRAME_HEIGHT);
    int type = CV_8UC3;  // 假设图像类型为 8 位 3 通道彩色图像

    // 计算图像数据的大小
    size_t imageDataSize = width * height * CV_ELEM_SIZE(type);

    // 创建共享内存
    int shmFd = shm_open("/video_shm", O_CREAT | O_RDWR, 0666);
    if (shmFd == -1) {
        std::cerr << "Failed to create shared memory" << std::endl;
        return 1;
    }
    size_t shmSize = sizeof(int) * 3 + imageDataSize + sizeof(double);  // 计算共享内存大小
    ftruncate(shmFd, shmSize);
    void* sharedMemory = mmap(NULL, shmSize, PROT_READ | PROT_WRITE, MAP_SHARED, shmFd, 0);
    if (sharedMemory == MAP_FAILED) {
        std::cerr << "Failed to map shared memory" << std::endl;
        return 1;
    }

    // 获取共享内存指针
    char* dataPtr = static_cast<char*>(sharedMemory);

    // 逐帧读取并发送
    cv::Mat frame;
    while (cap.read(frame)) {
        // 将图像尺寸复制到共享内存
        memcpy(dataPtr, &width, sizeof(int));
        dataPtr += sizeof(int);
        memcpy(dataPtr, &height, sizeof(int));
        dataPtr += sizeof(int);
        memcpy(dataPtr, &type, sizeof(int));
        dataPtr += sizeof(int);

        // 将图像数据复制到共享内存
        memcpy(dataPtr, frame.data, imageDataSize);
        dataPtr += imageDataSize;

        // 将帧率信息复制到共享内存
        memcpy(dataPtr, &fps, sizeof(double));

        // 等待接收方读取共享内存
        usleep(1000);

        // 打印帧率
        std::cout << "Sent FPS: " << fps << std::endl;
    }

    // 关闭共享内存
    munmap(sharedMemory, shmSize);
    close(shmFd);
    shm_unlink("/video_shm");

    return 0;
}