Technology for interactive stories: Dynamic videos

At ForUs, we are building engaging and interactive conversations, which educate people about ways to handle their financial situation.

Unlike regular educational video, we build interactive conversations. The user is presented with the set of educational materials and questions, which they can answer. The conversation flow depends on the answers of a user.

Right now I’m experimenting with various ways to utilize the technology to tell the story. Here are some interesting lessons learned. This post is about using different videos for each scene.

Presenting user choices

Once the video scene is over, I need to react and present the choices to a user. Question is, how do I know that the video is over?

First attempt to use the video ended event and present user choices at the moment, when the video stopped playing. This one did not work. When building interactive conversations, the last scene of a video presents an opportunity to naturally bring choices to a user, so the user feels like prompts are the part of the natural experience. Thus the video needs to be stopped on the last scene. The default behavior of the player is to auto-rewind the video to the first frame once it is done playing.

To solve this problem, I had to use timeupdate event and pause the video on the last scene. We have to make the last significant scene a second before the video ends.

  timeupdate: function(e) {
    var max_duration;
    max_duration = this.vPlayer.duration() - 1;
    if (max_duration > 0 && this.vPlayer.currentTime() > max_duration) {
      return this.$el.trigger('finished_scene');

The container listening to the events “finished_scene” will present choices to the user.

Stitching videos together

First lesson, learned about dynamically building a conversation from videos is that swapping them is not as easy as swapping other DOM elements. Video is played as part of the video player element. Dynamically reloading the video player instance every we need to play the next scene will not produce satisfactory user experience. It produces ugly flicks, which break user engagement with the story. I used video.js, which is open source and has reasonably good documentation.

I noticed flickering, which break the user engagement. The solution was fairly simple, but not obvious.

  1. Instead of reloading the player I started reloading the video source, while the instance of the player stayed the same.
  2. Just modifying video source is not as easy as it sounds. I found that the video player still was in the pause mode and source change will not start the video. The only way to play the video after the source was changed was only by calling play() method before source change to switch the player to play mode.
  3. Video player still works as the video tape and rmembers the position, where it was before the source change. It is necessary to “rewind” the video to the begining before chaging source.

Here is the final script, which I use to reset video player before swapping source:

  reset_player: function() {
    if (this.vPlayer.currentSrc()) {

Optimizing video load

Main challenge, we’ve found on the quest of keeping the user engaged, is the video load speed of an interactive conversation video. Each portion of the video needs to start playing instantly. We found that 360p video resolution delivers acceptable load speed for the average users. Going higher quality will not work.

In order to understand the real user experience, I measured the timing between the moment I request video play till the moment the user sees the first frame. In order to capture the moment, I use play event, which is fired at the moment when video loading is complete and the user sees the first frame.

I also use mixpanel to aggregate the metrics.

We consider acceptable video load performance to be between 0.5 and 1 second. This speed allows the video conversation to go smoothly with no noticeable delays.

Our experiments demonstrated that ETA can not be achieved consistently using traditional cloud providers. In order to consistently deliver this ETA, I’m working on video pre-loading technology. It will allow loading videos for further interactions while the user is engaged with previous steps.

Final remarks: Here is the page to learn more about HTML5 video and events: HTML5 Video Events and API

Sergey Zelvenskiy 11 January 2013