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Monday, October 23, 2006

Size of Captivate Files

In reference to my article Captivate File Size Tricks for Software Training via Simulations, I was just asked:
I was hoping you could answer a real easy question for me?

For an enterprise wide LMS system, would a Captivate movie (file) that is 1.5mb or less too big? I think this file size is micro, and that for real good elearning a file size of 40+mb is getting to a threshold. But these are tiny files, and I want to make sure we don’t get any pushback from IT on slow load times being a result of file sizes.

First, when you ask a question, never say its "real easy" - at least not to a developer. Anytime someone says the word "easy" - you generally should look out! :)

Let me start my answer by saying that if you are doing this within the US only, and on high speed connections, then 1.5mb should be no problem. That said, if you are international and/or have people running on slower connection speeds, you should be aware of two possible speed issues: load time and streaming issues.

With Captivate, theoretically the movies should have some initial load time and then should stream the remainder of the content while you are going through the movie. I personally believe (but am not sure) that larger movies have longer up-front load times. Still, I wouldn't be all that concerned with a 1.5 MB file. I would with a 40MB file.

You should also check out what is being reported in the bandwidth monitor. As long as the streaming requirements are reasonably below the line of your slower connection speeds, you should be in good shape for streaming.

All that said, one of the bigger reasons for splitting up the files is just authoring / managing large files in Captivate itself. Again, though, our experience says that 1.5MB (with audio) is not that big.

If any blog readers have had challenges with Captivate file sizes and want to help, please comment.


Jesse Ezell said...

There are limits to what Flash can do. Large file sizes are definitely not a good with the Flash player. However, I would be more worried about length than file size. After a certain number of frames, audio just plain loses sync in a Flash file because of some flaws in the design that didn't anticipate long movies. FLV has this fixed though if you export your videos to FLV instead of SWF.

Tony Karrer said...

Jesse, good point, but it's not been much of an issue on software sim kinds of courses for us given that you aren't normally going for that absolute of a sync. We did run into issues with a really big promo piece one time, but it was huge.

Do you have any idea of where this starts to come up? 10 min? 10MB? When should I begin to worry?

I'll have to look at using FLV.

Jesse Ezell said...

It's kinda fuzzy, but here is the advice straight from Adobe:

There is a magic number of 16,000 frames that you aren't supposed to exceed, which at 30 fps is just shy of 9 minutes.

Tony Karrer said...

Hmmm ... something doesn't sound quite right on that. Does Captivate really translate directly according to FPS into Flash frames? I know that we've created single Captivate movies that are longer than 10 minutes. I think Frames and FPS turn out to be different because one is design time issue and the other is playback. Wow, this is fuzzier than I thought it would be!

Jesse Ezell said...

Flash actually doesn't even maintain FPS unless you have a streaming audio track behind the movie. Even when you do have a streaming audio track, the issue is that MP3 frames and SWF frames are both playing a different frame rates (I believe MP3 frames are fixed at 26 fps... been a while since I wrote my SWF->MP3 conversion code though). Eventually the small errors add up and things get out of sync.

You can theoretically go higher than the 16,000 frame limit. It just isn't recommended because the format doesn't really support it completely. This is actually an issue that comes up every once and a while with something like Articulate Presenter, so we recommend people use lots of shorter slides than try to use something like 10 slides for a 2 hour presentation (don't ask me why people thought that was a good idea, but it happens).