memcpy(buf,&buffer[deltaValue +4],FrameLength);转成java
时间: 2024-02-27 11:57:09 浏览: 29
在Java中,可以使用System.arraycopy()方法来替代C语言中的memcpy()函数,将一个数组中的一段数据复制到另一个数组中。具体实现如下:
```java
System.arraycopy(buffer, deltaValue + 4, buf, 0, FrameLength);
```
其中,buffer是源数组,deltaValue + 4是源数组的起始位置,buf是目标数组,0是目标数组的起始位置,FrameLength是需要复制的数据长度。
相关问题
v4l2 c++显示摄像头
要在 C++ 中显示摄像头,可以使用 V4L2(Video for Linux 2)库。以下是一个简单的示例代码,可以帮助你开始显示摄像头:
```c++
#include <iostream>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
#include <opencv2/opencv.hpp>
#define CAMERA_DEVICE "/dev/video0"
#define CAPTURE_WIDTH 640
#define CAPTURE_HEIGHT 480
using namespace std;
using namespace cv;
int main()
{
int fd;
struct v4l2_capability cap;
struct v4l2_format fmt;
struct v4l2_requestbuffers req;
struct v4l2_buffer buf;
void* buffer_start;
unsigned int i;
// 打开摄像头设备
fd = open(CAMERA_DEVICE, O_RDWR);
if (fd == -1)
{
cout << "无法打开摄像头设备" << endl;
return -1;
}
// 查询摄像头设备信息
if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1)
{
cout << "无法查询摄像头设备信息" << endl;
close(fd);
return -1;
}
// 设置摄像头格式
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = CAPTURE_WIDTH;
fmt.fmt.pix.height = CAPTURE_HEIGHT;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUV420;
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
if (ioctl(fd, VIDIOC_S_FMT, &fmt) == -1)
{
cout << "无法设置摄像头格式" << endl;
close(fd);
return -1;
}
// 请求摄像头缓冲区
req.count = 4;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
if (ioctl(fd, VIDIOC_REQBUFS, &req) == -1)
{
cout << "请求摄像头缓冲区失败" << endl;
close(fd);
return -1;
}
// 映射摄像头缓冲区
buffer_start = malloc(req.count * sizeof(*buffer_start));
if (!buffer_start)
{
cout << "映射摄像头缓冲区失败" << endl;
close(fd);
return -1;
}
for (i = 0; i < req.count; i++)
{
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
if (ioctl(fd, VIDIOC_QUERYBUF, &buf) == -1)
{
cout << "无法查询摄像头缓冲区" << endl;
close(fd);
return -1;
}
*((void**)buffer_start + i) = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
if (*((void**)buffer_start + i) == MAP_FAILED)
{
cout << "无法映射摄像头缓冲区" << endl;
close(fd);
return -1;
}
}
// 将缓冲区入队
for (i = 0; i < req.count; i++)
{
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
if (ioctl(fd, VIDIOC_QBUF, &buf) == -1)
{
cout << "无法将缓冲区入队" << endl;
close(fd);
return -1;
}
}
// 开始采集
enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (ioctl(fd, VIDIOC_STREAMON, &type) == -1)
{
cout << "无法开始采集" << endl;
close(fd);
return -1;
}
// 显示帧图像
Mat frame(CAPTURE_HEIGHT, CAPTURE_WIDTH, CV_8UC3);
while (true)
{
// 获取缓冲区
if (ioctl(fd, VIDIOC_DQBUF, &buf) == -1)
{
cout << "无法获取缓冲区" << endl;
close(fd);
return -1;
}
// 处理图像
memcpy(frame.data, *((void**)buffer_start + buf.index), buf.bytesused);
// 将缓冲区重新入队
if (ioctl(fd, VIDIOC_QBUF, &buf) == -1)
{
cout << "无法将缓冲区重新入队" << endl;
close(fd);
return -1;
}
// 显示图像
imshow("camera", frame);
waitKey(1);
}
// 停止采集
if (ioctl(fd, VIDIOC_STREAMOFF, &type) == -1)
{
cout << "无法停止采集" << endl;
close(fd);
return -1;
}
// 释放缓冲区
for (i = 0; i < req.count; i++)
{
munmap(*((void**)buffer_start + i), buf.length);
}
free(buffer_start);
// 关闭摄像头设备
close(fd);
return 0;
}
```
这段代码使用了 OpenCV 库来显示图像,需要在编译时链接该库。你可以使用以下命令进行编译:
```
g++ -o camera camera.cpp `pkg-config opencv --cflags --libs`
```
请注意,这段代码可能需要根据你的摄像头设备和环境进行调整。你需要根据自己的需求修改它。
你可以帮我写个v4l2框架的camera取流代码
当然可以,以下是一个简单的v4l2框架的camera取流代码示例:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
#define CAMERA_DEVICE "/dev/video0"
#define CAPTURE_FILE "frame.raw"
#define IMAGE_WIDTH 640
#define IMAGE_HEIGHT 480
#define BUFFER_COUNT 4
struct buffer {
void *start;
size_t length;
};
struct buffer buffers[BUFFER_COUNT];
int main(int argc, char **argv) {
int fd;
struct v4l2_capability cap;
struct v4l2_format fmt;
struct v4l2_requestbuffers req;
enum v4l2_buf_type type;
fd_set fds;
struct timeval tv;
int r, i, j;
char *p;
size_t n;
FILE *fp;
fd = open(CAMERA_DEVICE, O_RDWR);
if (fd == -1) {
perror("open");
return EXIT_FAILURE;
}
if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1) {
perror("VIDIOC_QUERYCAP");
return EXIT_FAILURE;
}
if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
fprintf(stderr, "The device does not support video capture.\n");
return EXIT_FAILURE;
}
if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
fprintf(stderr, "The device does not support streaming i/o.\n");
return EXIT_FAILURE;
}
memset(&fmt, 0, sizeof(fmt));
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = IMAGE_WIDTH;
fmt.fmt.pix.height = IMAGE_HEIGHT;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
if (ioctl(fd, VIDIOC_S_FMT, &fmt) == -1) {
perror("VIDIOC_S_FMT");
return EXIT_FAILURE;
}
memset(&req, 0, sizeof(req));
req.count = BUFFER_COUNT;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
if (ioctl(fd, VIDIOC_REQBUFS, &req) == -1) {
perror("VIDIOC_REQBUFS");
return EXIT_FAILURE;
}
for (i = 0; i < BUFFER_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("VIDIOC_QUERYBUF");
return EXIT_FAILURE;
}
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("mmap");
return EXIT_FAILURE;
}
}
for (i = 0; i < BUFFER_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_QBUF, &buf) == -1) {
perror("VIDIOC_QBUF");
return EXIT_FAILURE;
}
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (ioctl(fd, VIDIOC_STREAMON, &type) == -1) {
perror("VIDIOC_STREAMON");
return EXIT_FAILURE;
}
fp = fopen(CAPTURE_FILE, "wb");
if (fp == NULL) {
perror("fopen");
return EXIT_FAILURE;
}
for (i = 0; i < 100; i++) {
FD_ZERO(&fds);
FD_SET(fd, &fds);
tv.tv_sec = 2;
tv.tv_usec = 0;
r = select(fd + 1, &fds, NULL, NULL, &tv);
if (r == -1) {
perror("select");
return EXIT_FAILURE;
}
if (r == 0) {
fprintf(stderr, "select timeout\n");
return EXIT_FAILURE;
}
memset(&buffers[i % BUFFER_COUNT], 0, sizeof(struct buffer));
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("VIDIOC_DQBUF");
return EXIT_FAILURE;
}
memcpy(buffers[buf.index].start, (void *)buf.m.offset, buf.bytesused);
buffers[buf.index].length = buf.bytesused;
if (fwrite(buffers[buf.index].start, 1, buffers[buf.index].length, fp) != buffers[buf.index].length) {
perror("fwrite");
return EXIT_FAILURE;
}
if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
perror("VIDIOC_QBUF");
return EXIT_FAILURE;
}
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (ioctl(fd, VIDIOC_STREAMOFF, &type) == -1) {
perror("VIDIOC_STREAMOFF");
return EXIT_FAILURE;
}
for (i = 0; i < BUFFER_COUNT; i++) {
if (munmap(buffers[i].start, buffers[i].length) == -1) {
perror("munmap");
return EXIT_FAILURE;
}
}
if (fclose(fp) == EOF) {
perror("fclose");
return EXIT_FAILURE;
}
if (close(fd) == -1) {
perror("close");
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
```
这段代码使用了v4l2框架来从摄像头中获取视频流,并将每一帧保存到文件中。你可以根据自己的需求进行修改。
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