delay in ouput of combined c++ program - c++

Question

i have two programs in c++. one is to communicate with arduino(pgm1),while the other is an openCV program reading a webcam(pgm2). independently, they work at moral speed.
if we open them simultaneously in different terminals they work perfect.i wanted to join them as a single program, i tried a program (pgm3). i can get images perfectly in real time.. but the data from arduino delays about 7-10 seconds. unfortunately i know only c/c++/embedded c. so kindly refer me a solution in any one of these languages
pgm1
#include<iostream>
#include<fstream>
using namespace std;
int main()
{
char ch;
ifstream f;
f.open("/dev/ttyACM0");
while (f.get(ch))
{
cout<<ch;
if(ch=='#')
cout<<endl;
}
return 0;
pgm2
#include "opencv2/objdetect.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <iostream>
#include <stdio.h>
using namespace std;
using namespace cv;
/** Function Headers */
String window_name = "webcam c170 preview";
/** #function main */
int main( void )
{
VideoCapture capture;
Mat frame;
capture.open( 1 );
if ( ! capture.isOpened() ) { printf("--(!)Error opening video capture\n"); return -1; }
while ( capture.read(frame) )
{
if( frame.empty() )
{
printf(" --(!) No captured frame -- Break!");
break;
}
//-- 3. show frames
imshow( window_name, frame );
int c = waitKey(30);
if( (char)c == 27 ) { break; } // escape
}
return 0;
}
}
pgm3
#include "opencv2/objdetect.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
#include <iostream>
#include <stdio.h>
#include<fstream>
using namespace std;
using namespace cv;
void spi_read(void);
/** Global variables */
char ch;
ifstream f;
String window_name = "webcam c170 preview";
/** #function main */
int main( void )
{
VideoCapture capture;
Mat frame;
f.open("/dev/ttyACM0");
capture.open( 1 );
if ( ! capture.isOpened() ) { printf("--(!)Error opening video capture\n"); return -1; }
while ( capture.read(frame) )
{
if( frame.empty() )
{
printf(" --(!) No captured frame -- Break!");
break;
}
//-- 3. show frames
imshow( window_name, frame );
int c = waitKey(30);
if( (char)c == 27 ) { break; } // escape
spi_read();
}
return 0;
}
void spi_read()
{
String str_spi;
do
{
f.get(ch);
str_spi=str_spi+ch;
}while(ch!='#');
cout<<str_spi<<endl;
}

Answer 1

Do not just merge to code into one function - of course it will cause your second program to "delay" - because its starts to execute after ur previos code is done.
You should create separate thread to simulate ur pgm1/pgm2 programs and then maybe process data received by them in ur main thread - depending on your needs.
Most straighforward solution using boost/thread:
void do_what_pgm1_does() {..}
void do_what_pgm2_does() {..}
int main()
{
boost::thread t1(do_what_pgm1_does);
boost::thread t2(do_what_pgm2_does);
t1.join();
t2.join();
}
this will give you similar execution as you had with 2 processes.