var prevVideoId;
var prevVideoImage;
  
function changeClipVideo(selectedVideoId, imageURL) {
 if (prevVideoId != undefined) {
  document.getElementById(prevVideoId).src = prevVideoImage;
 }
 var imageElement = document.getElementById('video_'+selectedVideoId);
 prevVideoId = 'video_'+selectedVideoId;
 prevVideoImage = imageElement.src;
 imageElement.src = imageURL;
}

function setPresentationText(selectedVideoId) {
    var textDiv = document.getElementById('videoPresentation');
    textDiv.innerHTML = eval('videoPresentation_'+selectedVideoId);
}