cannot detect file - file path problem?

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Hi,

Sorry if this is a dumb question but I am trying to use openCV with ROS to load an .avi file unsuccessfully.

To test out video loading, I used a very simple sample code online http://nashruddin.com/How_to_Play_AVI_Files_with_OpenCV and just modify line 22 to change the argument from argv[1] to "myvideo.avi" which is in the same folder as the source. I compile using g++ and it works as expected.

When I put that same source file into a ROS package my_ros_package/src and compile in ROS, the executable goes into my_ros_package/bin. So I tried putting myvideo.avi into both /bin and /src. Although the program compile fine using rosmake or make, when I load the executable, the code would return at line 25, implying that the .avi file could not be found.

I also tried various ways such as using rosrun or ./bin/my_executatble in my_ros_package or ./my_executable in my_ros_package/bin, all gave the same error.

Interestingly, if I only load an image instead of an .avi from the same code (using cvLoadImage("myimage.png"), the image can be diplayed when it is in the /bin folder and using ./my_executable in my_ros_package/bin.

I thought this could be a codec problem, I fixed it as suggested in the same link with the sample code, however, that did not work. Also, please note that the .avi could be played by using g++ for compiling and having the .avi file in the same folder with the source.

I am guessing the problem lies in the way ROS is setting its PATH. Could any one help out with this please?

Below is my source code

the video file & source file is in the same ros_package/src/ folder

This is the code that does not work as I compile from rosmake. The output returns "Cannot capture from AVI"

   #include <stdio.h>
    #include <iostream>
    #include "cv.h"
    #include "highgui.h"
    #include "ros/ros.h"
    #include "ros/package.h"


using namespace std;
using namespace ros::package;

int main( int argc, char** argv )
{
    IplImage  *frame;
    int key = 0;

    std::string DIR = getPath("iCharibot_face");
    std::string PATH = DIR + "/src/Talking4.avi";
    cout << "PATH " << PATH << endl;

    /* load the AVI file */
    CvCapture *capture = cvCaptureFromAVI(PATH.c_str());
    if(!capture){
         printf("Cannot capture from AVI.\n");
    }

    /* get fps, needed to set the delay */
    int fps = ( int )cvGetCaptureProperty( capture, CV_CAP_PROP_FPS );
   //int fps = 30;
    /* display video */
    cvNamedWindow( "video", 0 );

    while( key != 'q' ) {
        /* get a frame */
        frame = cvQueryFrame( capture );
        /* always check */
        if( !frame ) break;
        /* display frame */
        cvShowImage( "video", frame );

        /* quit if user press 'q' */
        key = cvWaitKey( 1000 / fps );
    }

    /* free memory */
    cvReleaseCapture( &capture );
    cvDestroyWindow( "video" );

    return 0;
}

The same code works fine even if I do not use the PATH when I use g++ to compile (I have to remove all the ros include to compile in g++). The Talking4.avi video is animated.

#include <stdio.h>
#include <iostream>
#include "cv.h"
#include "highgui.h"


using namespace std;

int main( int argc, char** argv )
{
    IplImage  *frame;
    int key = 0;

    /* load the ...