无人机之眼 | ROS图像RTMP协议推流到地面站，CPU表示软件解码

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一、Nginx服务器搭建

因为要将处理过的图片串成rtmp码流，因此，需要搭建一个rtmp服务器，常用的方案是Nginx服务器。

1.1 安装依赖 sudo apt-get update sudo apt-get install -y openssl libssl-dev libpcre3 libpcre3-dev zlib1g-dev sudo apt-get install -y autoconf automake build-essential git libass-dev libfreetype6-dev libsdl2-dev libtheora-dev libtool libva-dev libvdpau-dev libvorbis-dev libxcb1-dev libxcb-shm0-dev libxcb-xfixes0-dev pkg-config texinfo wget zlib1g-dev sudo apt-get install -y ffmpeg 1.2 编译源码 在工作空间下，新建一个nginx文件夹，用来存放需要下载nginx和nginx-rtmp-module两个安装包源码。 nginx下载链接，nginx-rtmp-module下载链接。 解压文件，生成nginx-1.18.0文件夹，生成nginx-rtmp-module文件夹。 然后编译安装nginx，cd进nginx的目录。 cd nginx-1.18.0 ./configure --add-module=../nginx-rtmp-module make -j4 sudo make install 1.3 测试nginx 直接运行以下命令：

sudo /usr/local/nginx/sbin/nginx 在浏览器中输入localhost：80（或者服务器的IP），看到如下画面，表示安装成功。 file 1.4 配置 编辑 /usr/local/nginx/conf/nginx.conf文件（）。sudo gedit /usr/local/nginx/conf/nginx.conf

#user nobody; worker_processes 1; #error_log logs/error.log; #error_log logs/error.log notice; #error_log logs/error.log info; #pid logs/nginx.pid; events { worker_connections 1024; } rtmp {
server { listen 1935; # 服务端口--默认 chunk_size 4096; # 数据传输块的大小--默认 #设置直播的application名称是live application live { live on; # live on表示开启直播模式 } } } http { include mime.types; default_type application/octet-stream; #log_format main 'remoteaddr−remote_addr - remote_user [timelocal]"time_local] "request" ' #'statusstatus body_bytes_sent "http_referer" ' #http_user_agent" "$http_x_forwarded_for"'; #access_log logs/access.log main; sendfile on; #tcp_nopush on; #keepalive_timeout 0; keepalive_timeout 65; #gzip on; server { listen 80; server_name localhost; #charset koi8-r; #access_log logs/host.access.log main; location / { root html; index index.html index.htm; } location /info { rtmp_stat all; rtmp_stat_stylesheet stat.xsl; } location /stat.xsl { root html; } #error_page 404 /404.html; #redirect server error pages to the static page /50x.html #error_page 500 502 503 504 /50x.html; location = /50x.html { root html; } } } 配置完之后，需要重启nginx：

sudo cp nginx-rtmp-module/stat.xsl /usr/local/nginx/html/ sudo /usr/local/nginx/sbin/nginx -s reload 然后在浏览器中输入localhost:80/info可看到如下画面： file 至此，完成了rtmp-nginx服务器的全部配置。

1.5 让系统启动时自动加载nginx服务

首先需要安装sysv-rc-conf： sudo apt-get update apt install sysv-rc-conf 设置nginx开机启动： 先为nginx在下创建一个启动脚本/etc/init.d/

gedit /etc/init.d/nginx 添加内容如下：

#! /bin/sh #chkconfig: 2345 55 25 #Description: Startup script for nginx webserver on Debian. Place in /etc/init.d and #run 'update-rc.d -f nginx defaults', or use the appropriate command on your #distro. For CentOS/Redhat run: 'chkconfig --add nginx' ###BEGIN INIT INFO #Provides: nginx #Required-Start: all #Required-Stop: all# Default-Start: 2 3 4 5 #Default-Stop: 0 1 6 #Short-Description: starts the nginx web server #Description: starts nginx using start-stop-daemon ###END INIT INFO #Author: licess #website: lnmp.org PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin NAME=nginx NGINX_BIN=/usr/local/nginx/sbin/NAMECONFIGFILE=/usr/local/nginx/conf/NAME CONFIGFILE=/usr/local/nginx/conf/NAME.conf PIDFILE=/usr/local/nginx/logs/NAME.pidcase"NAME.pid case "1" in start) echo -n "Starting $NAME... "

    if netstat -tnpl | grep -q nginx;then
        echo "$NAME (pid `pidof $NAME`) already running."
        exit 1       
    fi
    
    $NGINX_BIN -c $CONFIGFILE
    
    if [ "$?" != 0 ] ; then
        echo " failed"
        exit 1        else
        echo " done"
    fi
    ;;


stop)        
   echo -n "Stoping $NAME... "


    if ! netstat -tnpl | grep -q nginx; then
        echo "$NAME is not running."
        exit 1       
    fi


    $NGINX_BIN -s stop        
    
    if [ "$?" != 0 ] ; then
        echo " failed. Use force-quit"
        exit 1       
    else
        echo " done"
    fi
    ;;


status)        
    if netstat -tnpl | grep -q nginx; then
        PID=`pidof nginx`
        echo "$NAME (pid $PID) is running..."
    else
        echo "$NAME is stopped"
        exit 0        fi
    ;;


force-quit)        
    echo -n "Terminating $NAME... "


    if ! netstat -tnpl | grep -q nginx; then
        echo "$NAME is not running."
        exit 1        
    fi


    kill `pidof $NAME`


    if [ "$?" != 0 ] ; then
        echo " failed"
        exit 1       
    else
        echo " done"
    fi
    ;;


restart)        
    $0 stop
    sleep 1       
    $0 start
    ;;


reload)        echo -n "Reload service $NAME... "


    if netstat -tnpl | grep -q nginx; then
        $NGINX_BIN -s reload            
        echo " done"
    else
        echo "$NAME is not running, can't reload."
        exit 1        
    fi
    ;;


configtest)       
    echo -n "Test $NAME configure files... "


    $NGINX_BIN -t
    ;;   
    
*)        
    echo "Usage: $0 {start|stop|force-quit|restart|reload|status|configtest}"
    exit 1
    ;;

esac 保存成功之后我们要对这个管理脚本设置一个权限： chmod +x /etc/init.d/nginx 接下来我们可以看看这个脚本能否正确执行： /etc/init.d/nginx restart 这个管理脚本支持的命令有start|stop|force-quit|restart|reload|status|configtest。

如果没有错误能正确执行，那我们可以开始把他加入启动项了： sysv-rc-conf --list # 我们先查看一下list中有没有我们刚刚加进去的这个nginx管理脚本 sysv-rc-conf nginx on # 然后用这个命令添加开机自启动

二、运行Prometheus推流示例程序（Python编写）

运行如下命令：

roslaunch prometheus_detection web_cam0.launch # 打开一个usb摄像头0 roslaunch prometheus_detection rtmp_stream.launch # 开始推流 具体的Python推流代码如下（位置在）：

Prometheus/Modules/object_detection/py_nodes/rtmp_stream/ocv_rtmp_stream.py#!/usr/bin/env python #-- coding: utf-8 -- import rospy from sensor_msgs.msg import Image from geometry_msgs.msg import Pose, Point, Quaternion from cv_bridge import CvBridge from std_msgs.msg import String from std_msgs.msg import Bool import numpy as np import cv2 import subprocess import os import yaml import math rospy.init_node('rtmp_stream', anonymous=True) rtmp = r'rtmp://localhost:1935/live' size_str = str(640) + 'x' + str(400) command = ['ffmpeg', '-y', '-an', '-f', 'rawvideo', '-vcodec','rawvideo', '-pix_fmt', 'bgr24', '-s', size_str, '-r', '25', '-i', '-', '-c:v', 'libx264', '-pix_fmt', 'yuv420p', '-preset', 'ultrafast', '-f', 'flv', rtmp] pipe = subprocess.Popen(
command,
shell=False,
stdin=subprocess.PIPE )

def image_callback(imgmsg):
bridge = CvBridge()
frame = bridge.imgmsg_to_cv2(imgmsg, "bgr8")
#processing #end

   h, w = frame.shape[:2]    
   img_resize = 400
   if h > w:        
   h = int(float(h) / w * img_resize)       
   w = img_resize
   else:        
   w = int(float(w) / h * img_resize)        
   h = img_resize
   frame = cv2.resize(frame, (w, h))    
   frame = frame[:, :640, :]    
   pipe.stdin.write(frame.tostring())    
   cv2.imshow("cap", frame)    
   #cv2.imshow("area", area)
   cv2.waitKey(10)

def rtmp_stream(topic_name):
rospy.Subscriber(topic_name, Image, image_callback)
rospy.spin()

if name == 'main':
subscriber = rospy.get_param('~camera_topic', '/prometheus/camera/rgb/image_raw')

 try:       
     rtmp_stream(subscriber)   
 except rospy.ROSInterruptException:       
     pass


 pipe.terminate()

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