qt使用摄像头问题 - QTCN开发网

//查询设备属性
    struct v4l2_capability cap;
    if(ioctl(camera_fd, VIDIOC_QUERYCAP, &cap) < 0) {
        qDebug() << TIMEMS << "error in VIDIOC_QUERYCAP";
        close(camera_fd);
        return false;
    }

    if(!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
        qDebug() << TIMEMS << "it is not a video capture device";
        close(camera_fd);
        return false;
    }

    if(!(cap.capabilities & V4L2_CAP_STREAMING)) {
        qDebug() << TIMEMS << "it can not streaming";
        close(camera_fd);
        return false;
    }

    if(cap.capabilities == 0x4000001) {
        qDebug() << TIMEMS << "capabilities:" << "V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING";
    }

    //设置视频输入源
    int input = 0;
    if(ioctl(camera_fd, VIDIOC_S_INPUT, &input) < 0) {
        qDebug() << TIMEMS << "error in VIDIOC_S_INPUT";
        close(camera_fd);
        return false;
    }

    //设置图片格式和分辨率
    struct v4l2_format fmt;
    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV ;//V4L2_PIX_FMT_YUV420  V4L2_PIX_FMT_YUYV
    fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
    fmt.fmt.pix.width = cameraWidth;
    fmt.fmt.pix.height = cameraHeight;

    if(ioctl(camera_fd, VIDIOC_S_FMT, &fmt) < 0) {
        close(camera_fd);
        return false;
    }

    //查看图片格式和分辨率,判断是否设置成功
    if(ioctl(camera_fd, VIDIOC_G_FMT, &fmt) < 0) {
        qDebug() << TIMEMS << "error in VIDIOC_G_FMT";
        close(camera_fd);
        return false;
    }

    //重新打印下宽高看下是否真正设置成功
    qDebug() << TIMEMS << "cameraWidth =" << cameraWidth << "cameraHeight =" << cameraHeight << "  width =" << fmt.fmt.pix.width << "height =" << fmt.fmt.pix.height;
    qDebug() << TIMEMS << "pixelformat =" << QString("%1%2%3%4").arg(QChar(fmt.fmt.pix.pixelformat & 0xFF)).arg(QChar((fmt.fmt.pix.pixelformat >> 8) & 0xFF)).arg(QChar((fmt.fmt.pix.pixelformat >> 16) & 0xFF)).arg(QChar((fmt.fmt.pix.pixelformat >> 24) & 0xFF));

    //重新设置宽高为真实的宽高
    cameraWidth = fmt.fmt.pix.width;
    cameraHeight = fmt.fmt.pix.height;

    //设置帧格式
    struct v4l2_streamparm parm;
    parm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    parm.parm.capture.timeperframe.numerator = 1;
    parm.parm.capture.timeperframe.denominator = 25;
    parm.parm.capture.capturemode = 0;

    if(ioctl(camera_fd, VIDIOC_S_PARM, &parm) < 0) {
        qDebug() << TIMEMS << "error in VIDIOC_S_PARM";
        close(camera_fd);
        return false;
    }

    if(ioctl(camera_fd, VIDIOC_G_PARM, &parm) < 0) {
        qDebug() << TIMEMS << "error in VIDIOC_G_PARM";
        close(camera_fd);
        return false;
    }

    //申请和管理缓冲区
    struct v4l2_requestbuffers reqbuf;
    reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    reqbuf.memory = V4L2_MEMORY_MMAP;
    reqbuf.count = 1;

    if(ioctl(camera_fd, VIDIOC_REQBUFS, &reqbuf) < 0) {
        qDebug() << TIMEMS << "error in VIDIOC_REQBUFS";
        close(camera_fd);
        return false;
    }

    img_buffers = (ImgBuffer *)calloc(1, sizeof(ImgBuffer));
    if(img_buffers == NULL) {
        qDebug() << TIMEMS << "error in calloc";
        close(camera_fd);
        return false;
    }

    struct v4l2_buffer buffer;
    for(int numBufs = 0; numBufs < 1; numBufs++) {
        buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buffer.memory = V4L2_MEMORY_MMAP;
        buffer.index = numBufs;

        if(ioctl(camera_fd, VIDIOC_QUERYBUF, &buffer) < 0) {
            qDebug() << TIMEMS << "error in VIDIOC_QUERYBUF";
            free(img_buffers);
            close(camera_fd);
            return false;
        }

        img_buffers[numBufs].length = buffer.length;
        img_buffers[numBufs].start = (quint8 *)mmap (NULL, buffer.length, PROT_READ | PROT_WRITE, MAP_SHARED, camera_fd, buffer.m.offset);
        if(MAP_FAILED == img_buffers[numBufs].start) {
            qDebug() << TIMEMS << "error in mmap";
            free(img_buffers);
            close(camera_fd);
            return false;
        }

        //把缓冲帧放入队列
        if(ioctl(camera_fd, VIDIOC_QBUF, &buffer) < 0) {
            qDebug() << TIMEMS << "error in VIDIOC_QBUF";
            for(int i = 0; i <= numBufs; i++) {
                munmap(img_buffers[i].start, img_buffers[i].length);
            }

            free(img_buffers);
            close(camera_fd);
            return false;
        }
    }

    enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    if(ioctl(camera_fd, VIDIOC_STREAMON, &type) < 0) {
        qDebug() << TIMEMS << "error in VIDIOC_STREAMON";
        for(int i = 0; i < 1; i++) {
            munmap(img_buffers[i].start, img_buffers[i].length);
        }

        free(img_buffers);
        close(camera_fd);
        return false;
    }

    qDebug() << TIMEMS << "init camera ok";
    return true;