V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE模式下如何获取视频，请针对/dev/video1进行实现给出实例

好的，下面是使用 V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE 模式从 /dev/video1 获取视频的基本步骤和代码示例：

1. 打开设备文件并设置视频格式

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>

#define WIDTH 640
#define HEIGHT 480
#define FORMAT V4L2_PIX_FMT_YUYV

int main() {
    int fd = open("/dev/video1", O_RDWR);
    if (fd < 0) {
        perror("Failed to open device");
        exit(EXIT_FAILURE);
    }

    struct v4l2_format fmt = {0};
    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
    fmt.fmt.pix_mp.width = WIDTH;
    fmt.fmt.pix_mp.height = HEIGHT;
    fmt.fmt.pix_mp.pixelformat = FORMAT;
    fmt.fmt.pix_mp.num_planes = 1;
    if (ioctl(fd, VIDIOC_S_FMT, &fmt) < 0) {
        perror("Failed to set format");
        exit(EXIT_FAILURE);
    }

    // 其他设置参数
    // ...

    // 缓冲区申请
    // ...
}

2. 请求和映射缓冲区

#define NUM_BUFFERS 4

struct buffer {
    void *start;
    size_t length;
};

struct buffer buffers[NUM_BUFFERS];

if (ioctl(fd, VIDIOC_REQBUFS, &(struct v4l2_requestbuffers){NUM_BUFFERS, V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE, V4L2_MEMORY_MMAP, 0}) < 0) {
    perror("Failed to request buffers");
    exit(EXIT_FAILURE);
}

for (int i = 0; i < NUM_BUFFERS; i++) {
    struct v4l2_buffer buf = {0};
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
    buf.memory = V4L2_MEMORY_MMAP;
    buf.index = i;
    if (ioctl(fd, VIDIOC_QUERYBUF, &buf) < 0) {
        perror("Failed to query buffer");
        exit(EXIT_FAILURE);
    }

    buffers[i].length = buf.m.planes[0].length;
    buffers[i].start = mmap(NULL, buffers[i].length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
    if (buffers[i].start == MAP_FAILED) {
        perror("Failed to map buffer");
        exit(EXIT_FAILURE);
    }
}

3. 将缓冲区放入队列并开始采集

for (int i = 0; i < NUM_BUFFERS; i++) {
    struct v4l2_buffer buf = {0};
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
    buf.memory = V4L2_MEMORY_MMAP;
    buf.index = i;
    buf.m.planes[0].m.fd = fd;
    buf.m.planes[0].length = buffers[i].length;
    buf.m.planes[0].bytesused = 0;
    buf.m.planes[0].data_offset = 0;
    if (ioctl(fd, VIDIOC_QBUF, &buf) < 0) {
        perror("Failed to queue buffer");
        exit(EXIT_FAILURE);
    }
}

if (ioctl(fd, VIDIOC_STREAMON, &(int){V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE}) < 0) {
    perror("Failed to start streaming");
    exit(EXIT_FAILURE);
}

4. 从队列中取出缓冲区并读取数据

struct v4l2_buffer buf = {0};
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
buf.memory = V4L2_MEMORY_MMAP;
if (ioctl(fd, VIDIOC_DQBUF, &buf) < 0) {
    perror("Failed to dequeue buffer");
    exit(EXIT_FAILURE);
}

// 处理数据
// ...

if (ioctl(fd, VIDIOC_QBUF, &buf) < 0) {
    perror("Failed to queue buffer");
    exit(EXIT_FAILURE);
}

5. 停止采集并释放缓冲区

if (ioctl(fd, VIDIOC_STREAMOFF, &(int){V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE}) < 0) {
    perror("Failed to stop streaming");
    exit(EXIT_FAILURE);
}

for (int i = 0; i < NUM_BUFFERS; i++) {
    if (munmap(buffers[i].start, buffers[i].length) < 0) {
        perror("Failed to unmap buffer");
        exit(EXIT_FAILURE);
    }
}

if (ioctl(fd, VIDIOC_REQBUFS, &(struct v4l2_requestbuffers){0, V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE, V4L2_MEMORY_MMAP, 0}) < 0) {
    perror("Failed to release buffers");
    exit(EXIT_FAILURE);
}

close(fd);

这是一个简单的从 /dev/video1 获取视频的实现示例，需要注意的是，不同的摄像头设备和驱动程序可能会有所不同，具体实现还需要根据实际情况进行调整。