Stream video from Raspberry pi to Opencv application on remote computer

Question

What I am trying to achieve is, I have a raspberry 3 with pi camera v2 connected to my local wifi. I want to transmit a live video from the raspberry pi to a computer running Ubuntu. On my computer I am trying to process that video with opencv in real time. The code below is just a sample code to test the video coming from the raspberry pi on my Ubuntu computer. I am using netcat to stream the video and I have listed the shell script below the code.

#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>
using namespace std;
using namespace cv;

int main(int argc, char** argv)
{


    VideoCapture cap;
    cap.open("/dev/stdin");
    if (!cap.isOpened())
        return -1;

    Mat edges;
    namedWindow("edges",1);
    for(;;){
        Mat frame;
        cap>>frame;
        imshow("edges",frame);
        if(waitKey(30)>=0)break;
    }   

    return 0;
}

This is the code to play the stream in opencv.

1. First I redirect the stream to my opencv app using. nc -l -p 5001 | ./app
2. then run I the raspberry camera and stream it using netcat raspivid -t 999999 -o | nc x.x.x.x 5001 x being the client pc ip address.

This doesn't work for me but I have tried it with mplayer by running nc -l -p 5001 | mplayer -fps 31 -cache 1024 - and it works perfectly.

I think my problem is I am not capturing the stream properly on my opencv application. I need help please.

Answer 1

I spent around 4 hours trying to make this work and got it working in the end. I am not certain which was the key step, nor why, but I found it all works if I install the following packages on my Ubuntu 16 LTS VirtualBox:

libtbb2
ffmpeg
libavcodec
libavcodec-dev
libavformat-dev
libtbb-dev
libswscale-dev
libgtk2.0-dev
libtbb-dev
libjpeg-dev
libpng-dev
libtiff-dev
libjasper-dev
libdc1394-22-dev
libv4l-dev
libx264-dev

and run the camera on my Raspberry Pi with:

raspivid -ih -w 1024 -h 768 -o - | nc 192.168.0.98 5001

Keywords: Raspberry Pi, RASPI, raspivid, camera, OpenCV, stream, streaming, netcat, nc, network, video