Video and image out of Sync

sometimes the video tag is not there yet when the script executes. Try this ( you can always log everything to see what's going on.):

var interval = setInterval( checkExists, 100, e );

function checkExists( e )
{
var vid = document.getElementsByTagName("video")[0];

  if ( vid.length > 0 )
{
  clearInterval(interval);
  vid.addEventListener("timeupdate",vidTimer,false);
}

function vidTimer()
{

if (vid.currentTime>4 && vid.currentTime<8)
{
  cp.show("txt_3Sec");
}
else
{
  cp.hide("txt_3Sec");
}

if (vid.currentTime>20)
{
  vid.removeEventListener("timeupdate",VidTimer,false);
}
}

You cannot name the video by the name of the video, it must be:

var vid = document.getElementsByTagName("video")[0];

You can use JavaScript to monitor the time update of a video, regardless of how long it takes to load. If you execute this on enter of the slide that has video, you can turn on and off elements and it will always be in-synch. You'd need to add your conditions in the vidTimer function.

var vid = document.getElementsByTagName("video")[0];
vid.addEventListener("timeupdate",vidTimer,false);

function vidTimer()
{  
if ( vid.currentTime > 37.5 && vid.currentTime < 41.7 )
{ 
  cp.show("user_name"); 
}
else
{
  cp.hide("user_name"); 
}

  if ( vid.currentTime > 42 )
{
  vid.removeEventListener("'timeupdate", vidTimer, false);
}
}

One of the things I have noticed with the movement away from flash and now working with html, server latency (loading time) is a bigger issue. In a recent project I just completed I created the slide with a 3 minute video and timed the objects that appear on the slide to the video in the Captivate timeline. I then published that slide as an mp4 which now has all the images and text smart shapes and audio in the video file.  I then placed that mp4 on the slide a as multi-slide video and it plays nicely in the timeline. Normally I would do this kind of video editing in Adobe Premiere, but I wanted to try it in Captivate and it appears to be working well for the project needs. I have also cut up larger videos into smaller pieces and distributed them over a number of slides as Lilybiri suggests and this has also helped with the loading issue. But again I find that its best to use Adobe Premiere for doing this for longer videos of more than say 2 minutes in duration. Its the only way I believe that you can ensure synchronization.

Problem is not with the images but with the video which needs loading time. Is it not possible to distribute the video and images over several slides to shorten loadig time on each slide?