Technically, how do FLVs progressively download in Captivate?

[Craig Mueller]

If a Captivate file has multiple .FLV files (say 5, 5 minutes videos)
set up as Progressive Downloads, how do the videos actually download
to the end user? Do they all download some initially or do they wait
to download until played, for example?

And, is it true that once a video is downloaded to a machine
subsequent viewings of the same video don’t need to be downloaded
again? In other words, the FLV is stored in the Temporary Internet
Files (cached) inevitably allowing for the second viewing to be
seamless?

I know this isn’t the best way to provide video but at this point, I’m
just trying to get the facts to my IT department about how the files,
described above, will impact the network.
-Craig

[Philip Hutchison]

Hi Craig

Progressive download videos can be played while they're downloading, before the download has completely finished. For example, when you start downloading a 10-minute video, it will start playing once it has a large enough chunk of video (buffer). While the video in initial buffer plays, the browser continues to download more of the video. When set up correctly, the next part of the video will have downloaded before you reach the end of your initial buffer, and you won't get any start-stop stuttering in your playback. (This is all assuming the viewer doesn't click around the playbar, trying to access parts of the video that haven't downloaded yet.)

In Flash Professional (and even HTML5) you have control of the buffer size. I don't recall if Captivate provides control of the buffer size.

Ideally you don't want it too big, because it will force the user to wait a long time before they can start the video. You also don't want it too small because the playback might be faster than the user's download speed, causing the video to stop/stutter. 

Regarding when the file downloads, typically a file won't start downloading until it's requested.  If you have a video on slide 5, it won't download until you get to page 5. There are ways to code around it and force preloading, but I don't believe Captivate preloads videos (I could be mistaken).

As far as caching, default browser behavior will cache the video, but the browser's cache gets turned over as it gets full. There's no guarantee the video will remain cached, especially if the learner closes the course, browses Faceb... err.. the web for a while, then comes back to the course a few days later.

Also, some people edit their cache settings to be short or completely disabled, while others might use the browser's private browsing feature, which would prevent the items from being saved beyond the current browsing session (available in all modern browsers, including Internet Explorer 9+).

- philip

-Craig

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