RK3399平台下如何获取视频数据

在RK3399平台上，您可以使用V4L2框架来获取视频数据。以下是获取视频数据的基本步骤：

1. 打开视频设备

fd = open("/dev/video0", O_RDWR);
if (fd == -1) {
    perror("Failed to open video device");
    return -1;
}

2. 查询视频设备的功能和参数

struct v4l2_capability cap;
if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1) {
    perror("Failed to query video device capabilities");
    return -1;
}

3. 设置视频格式和参数

struct v4l2_format fmt;
memset(&fmt, 0, sizeof(fmt));
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = WIDTH;
fmt.fmt.pix.height = HEIGHT;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
if (ioctl(fd, VIDIOC_S_FMT, &fmt) == -1) {
    perror("Failed to set video format");
    return -1;
}

4. 分配视频帧缓冲区

struct v4l2_requestbuffers req;
memset(&req, 0, sizeof(req));
req.count = NUM_BUFFERS;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
if (ioctl(fd, VIDIOC_REQBUFS, &req) == -1) {
    perror("Failed to request video buffers");
    return -1;
}

struct buffer *buffers = calloc(req.count, sizeof(*buffers));
if (!buffers) {
    perror("Failed to allocate video buffers");
    return -1;
}

for (int i = 0; i < req.count; i++) {
    struct v4l2_buffer buf;
    memset(&buf, 0, sizeof(buf));
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
    buf.index = i;
    if (ioctl(fd, VIDIOC_QUERYBUF, &buf) == -1) {
        perror("Failed to query video buffer");
        return -1;
    }

    buffers[i].length = buf.length;
    buffers[i].start = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
    if (buffers[i].start == MAP_FAILED) {
        perror("Failed to map video buffer");
        return -1;
    }

    if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
        perror("Failed to queue video buffer");
        return -1;
    }
}

5. 开始视频采集

enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (ioctl(fd, VIDIOC_STREAMON, &type) == -1) {
    perror("Failed to start video stream");
    return -1;
}

6. 读取视频帧数据

struct v4l2_buffer buf;
memset(&buf, 0, sizeof(buf));
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
if (ioctl(fd, VIDIOC_DQBUF, &buf) == -1) {
    perror("Failed to dequeue video buffer");
    return -1;
}

// Process video frame data here
process_frame(buffers[buf.index].start, buffers[buf.index].length);

if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
    perror("Failed to queue video buffer");
    return -1;
}

7. 停止视频采集和释放资源

if (ioctl(fd, VIDIOC_STREAMOFF, &type) == -1) {
    perror("Failed to stop video stream");
    return -1;
}

for (int i = 0; i < req.count; i++) {
    munmap(buffers[i].start, buffers[i].length);
}

free(buffers);
close(fd);

请注意，上述代码仅供参考，具体实现可能因设备驱动程序的不同而有所不同。您可以根据自己的需求和设备的驱动程序来进行适当的修改和调整。