Cannot play AVI files with Diamondback Debian OpenCV

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I can't seem to play AVI files using the latest ROS OpenCV Debian packages under Diamondback and Ubuntu 10.04. Is anyone else able to do this? I am wondering if the Debian packages were compiled without ffmpeg support? Googling around, I found a few sites that recommended first converting the original video like this:

$ mencoder original.avi -ovc raw -vf format=i420 -o out.avi

which I have done. I have then tried both Python and C++ programs to play the out.avi file, but neither produces any image. Here is the C++ source I tried just now:

/**
 * How to Play AVI Files with OpenCV
 *
 * Author  Nash
 * License GPL
 * Website http://nashruddin.com
 */

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

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

    /* supply the AVI file to play */
    assert( argc == 2 );

    /* load the AVI file */
    CvCapture *capture = cvCaptureFromAVI( argv[1] );

    /* always check */
    if( !capture ) return 1;

    int fps = ( int )cvGetCaptureProperty( capture, CV_CAP_PROP_FPS );

    /* 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 );
        key = cvWaitKey( 50 );
    }

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

    return 0;
}