Movie Transparent Alpha Channel

Jul 19, 2012

OK, let me make sure I have this straight, perhaps the community can enlighten me.

-- If I import a .mov movie that has a clear alpha channel into Storyline it will encode it into an .mp4 and I will loose the alpha channel.

-- If I import a .flv that has a clear alpha channel it will keep it unless an HTML 5 request comes and then Storyline will encode it into a .mp4 and loose the alpha channel.

--If I import a .mp4 with a clear alpha channel Storyline will re-encode it and wipe out my alpha channel.

So, the best approach appears to be to forget about movies with clear alpha channels if you suspect that any of your clients don't like Flash. And only .flv works.

34 Replies
Steve Flowers

I've used this technique in the distant past to good effect. Overlaying the video for non-interactive elements over the top of animated elements works pretty well and offers quite a bit of flexibility for maintenance. The ability to swap out the background is neat.

But it is complicated and modern browsers don't support it (at all). I've since dropped using the overlay and moved to a video underlay with a static background in the video or using an inset when an image / video of the presenter adds value. This works nearly as well, is easier to produce, and less finicky in deployment.

I'm not sure why it wouldn't be working, Heather. It could be an issue with SL2. The first version of Storyline handled alpha channel video well. Early versions of SL2 displayed a black background. Tough to tell if it's an encoding issue or a problem with SL2's video playback.

Ashley Terwilliger-Pollard

Hi Pete,

I saw you reach out in a few different discussions, and I did want to point out that Storyline 1 and 2 did support FLV/Alpha Channel as noted here.  You'll also see it noted here in this comparison chart for Storyline 360 of HTML5, Flash and AMP. 

In any of the Storyline versions, it's not supported in the HTML5 output. 

As for Aparna's earlier question, we don't have support for 3D videos in Storyline (alpha or not). 

Hope that clarifies! 

Steve Flowers

Biggest issue with this right now is alpha channel video is not currently supported in any browser. So this is less an issue with Storyline (or any authoring tool for that matter) and more an issue with the state of the Web right now. Flash made this convenient since it was built-in to the FLV spec. As far as I know, since there isn't a web video format that supports transparent video, nobody is able to run alpha channel video natively on the web. 

There are some computation intensive tricks that can be used to fake it. But it's not at all efficient or reliable and results in frame drops and high CPU usage. 

Ashley Terwilliger-Pollard

Hi Paul,

Since the FLV alpha channel transparency is supported in limited environment such as Flash enabled browsers, and Adobe has announced that they'll stop support for Flash in 2020 - it may be more time and cost effective to develop with the GIFs and be able to use the HTML5 output. 

I know there are a lot of other folks in the community using media like GIFs and FLV files, so I hope that they'll be able to share some info here too! 

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