if i play the video directly from the device where it is placed/installed then it plays perfectly. I am sending the video by placing it in a folder in my project & mentioning the path of that folder in the .pro file.
After the application is installed, i can see the same file at the correct location.
just an update: In the following code, if i uncomment the visible : false & playing: true lines then the audio is heard but video is not seen:
width : 600
height : 400
// visible: false;
// playing: true;