视频监控中使用usb摄像头(MJPG)代替OV5640
第二十八章 ，正点原子介绍使用他们的OV5640摄像头模组 ，但我手上只有usb摄像头，结果卡住了，视频怎么都出不来。
然后，查阅自己摄像头的参数，
v4l2-ctl -d /dev/video2 --all
查找怎么使用"MJPG"采集视频
网上翻了翻，有介绍“yuyv”的usb摄像头的（正点原子imx6ull: QT视频监控项目使用yuyv格式的usb摄像头_qt显示yuv摄像-CSDN博客），但我这款是“mjpg”的，还真给难住了，查阅了这篇博主的文章
https://zhuanlan.zhihu.com/p/721607842
关于MJPG蛮详细的，怎么去改。我这改三处，就成功了
/dev/video1
改成了
/dev/video2 ;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB565;
改成了
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;
QImage qImage((unsigned char*)bufs_info[n_buf].start, fmt.fmt.pix.width, fmt.fmt.pix.height, QImage::Format_RGB16);
改成了
QByteArray byteArray((const char*)bufs_info[n_buf].start, buf.bytesused);
QImage qImage;
qImage.loadFromData(byteArray, "JPEG"); // 从MJPEG数据中加载QImage.cpp 代码我放这里
/******************************************************************
Copyright © Deng Zhimao Co., Ltd. 2021-2030. All rights reserved.
* @projectName video_server
* @brief capture_thread.cpp
* @author Deng Zhimao
* @email dengzhimao@alientek.com
* @link www.openedv.com
* @date 2021-11-19
*******************************************************************/
#include "capture_thread.h"
void CaptureThread::run()
{
/* 下面的代码请参考正点原子C应用编程V4L2章节，摄像头编程，这里不作解释 */
#ifdef linux
#ifndef __arm__
return;
#endif
int video_fd = -1;
struct v4l2_format fmt;
struct v4l2_requestbuffers req_bufs;
static struct v4l2_buffer buf;
int n_buf;
struct buffer_info bufs_info[VIDEO_BUFFER_COUNT];
enum v4l2_buf_type type;
video_fd = open(VIDEO_DEV, O_RDWR);
if (0 > video_fd) {
printf("ERROR: failed to open video device %s\n", VIDEO_DEV);
return ;
}
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = 640;
fmt.fmt.pix.height = 480;
fmt.fmt.pix.colorspace = V4L2_COLORSPACE_SRGB;
// fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB565;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;
if (0 > ioctl(video_fd, VIDIOC_S_FMT, &fmt)) {
printf("ERROR: failed to VIDIOC_S_FMT\n");
close(video_fd);
return ;
}
req_bufs.count = VIDEO_BUFFER_COUNT;
req_bufs.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req_bufs.memory = V4L2_MEMORY_MMAP;
if (0 > ioctl(video_fd, VIDIOC_REQBUFS, &req_bufs)) {
printf("ERROR: failed to VIDIOC_REQBUFS\n");
return ;
}
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
for (n_buf = 0; n_buf < VIDEO_BUFFER_COUNT; n_buf++) {
buf.index = n_buf;
if (0 > ioctl(video_fd, VIDIOC_QUERYBUF, &buf)) {
printf("ERROR: failed to VIDIOC_QUERYBUF\n");
return ;
}
bufs_info[n_buf].length = buf.length;
bufs_info[n_buf].start = mmap(NULL, buf.length,
PROT_READ | PROT_WRITE, MAP_SHARED,
video_fd, buf.m.offset);
if (MAP_FAILED == bufs_info[n_buf].start) {
printf("ERROR: failed to mmap video buffer, size 0x%x\n", buf.length);
return ;
}
}
for (n_buf = 0; n_buf < VIDEO_BUFFER_COUNT; n_buf++) {
buf.index = n_buf;
if (0 > ioctl(video_fd, VIDIOC_QBUF, &buf)) {
printf("ERROR: failed to VIDIOC_QBUF\n");
return ;
}
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (0 > ioctl(video_fd, VIDIOC_STREAMON, &type)) {
printf("ERROR: failed to VIDIOC_STREAMON\n");
return ;
}
while (startFlag) {
for (n_buf = 0; n_buf < VIDEO_BUFFER_COUNT; n_buf++) {
buf.index = n_buf;
if (0 > ioctl(video_fd, VIDIOC_DQBUF, &buf)) {
printf("ERROR: failed to VIDIOC_DQBUF\n");
return;
}
// QImage qImage((unsigned char*)bufs_info[n_buf].start, fmt.fmt.pix.width, fmt.fmt.pix.height, QImage::Format_RGB16);
// 将MJPEG数据解码为QImage
QByteArray byteArray((const char*)bufs_info[n_buf].start, buf.bytesused);
QImage qImage;
qImage.loadFromData(byteArray, "JPEG"); // 从MJPEG数据中加载QImage
/* 是否开启本地显示，开启本地显示可能会导致开启广播卡顿，它们互相制约 */
if (startLocalDisplay)
emit imageReady(qImage);
/* 是否开启广播，开启广播会导致本地显示卡顿，它们互相制约 */
if (startBroadcast) {
/* udp套接字 */
QUdpSocket udpSocket;
/* QByteArray类型 */
QByteArray byte;
/* 建立一个用于IO读写的缓冲区 */
QBuffer buff(&byte);
/* image转为byte的类型，再存入buff */
qImage.save(&buff, "JPEG", -1);
/* 转换为base64Byte类型 */
QByteArray base64Byte = byte.toBase64();
/* 由udpSocket以广播的形式传输数据，端口号为8888 */
udpSocket.writeDatagram(base64Byte.data(), base64Byte.size(), QHostAddress::Broadcast, 8888);
}
if (0 > ioctl(video_fd, VIDIOC_QBUF, &buf)) {
printf("ERROR: failed to VIDIOC_QBUF\n");
return;
}
}
}
msleep(800);//at lease 650
for (int i = 0; i < VIDEO_BUFFER_COUNT; i++) {
munmap(bufs_info[i].start, buf.length);
}
close(video_fd);
#endif
}
.h我放这里
/******************************************************************
Copyright © Deng Zhimao Co., Ltd. 2021-2030. All rights reserved.
* @projectName video_server
* @brief capture_thread.h
* @author Deng Zhimao
* @email dengzhimao@alientek.com
* @link www.openedv.com
* @date 2021-11-19
*******************************************************************/
#ifndef CAPTURE_THREAD_H
#define CAPTURE_THREAD_H
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <pthread.h>
#ifdef linux
#include <linux/fb.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <linux/videodev2.h>
#include <linux/input.h>
#endif
#include <QThread>
#include <QDebug>
#include <QPushButton>
#include <QImage>
#include <QByteArray>
#include <QBuffer>
#include <QTime>
#include <QUdpSocket>
//#define VIDEO_DEV "/dev/video1"
#define VIDEO_DEV "/dev/video2"
#define FB_DEV "/dev/fb0"
#define VIDEO_BUFFER_COUNT 3
struct buffer_info {
void *start;
unsigned int length;
};
class CaptureThread : public QThread
{
Q_OBJECT
signals:
/* 准备图片 */
void imageReady(QImage);
void sendImage(QImage);
private:
/* 线程开启flag */
bool startFlag = false;
/* 开启广播flag */
bool startBroadcast = false;
/* 本地显示flag */
bool startLocalDisplay = false;
void run() override;
public:
CaptureThread(QObject *parent = nullptr) {
Q_UNUSED(parent);
}
public slots:
/* 设置线程 */
void setThreadStart(bool start) {
startFlag = start;
if (start) {
if (!this->isRunning())
this->start();
} else {
this->quit();
}
}
/* 设置广播 */
void setBroadcast(bool start) {
startBroadcast = start;
}
/* 设置本地显示 */
void setLocalDisplay(bool start) {
startLocalDisplay = start;
}
};
#endif // CAPTURE_THREAD_H