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January 16, 2009

Streaming Video Playback Speed Controls - Two Innovative Methods

One of the coolest playback features for online video, especially academic video, is a player with the ability to speed up (or slow down) the playback speed of a streaming video.  Way back in the early 2000's there was a tool called Enounce that acted as a plugin to RealPlayer or Windows Media Player and would add a control slider to the player.  Everything from half-speed to 5x playback, with no pitch change on the audio.  It was very effective for watching lectures or news content - for much material, you can really absorb it much faster than it's spoken.  Turns out that Enounce is still available, and works pretty well, and they announced a version called MySpeed which supports embedded Flash video.   

End-users can buy and install Enounce and use it on their systems.  It's a native Windows-only application and must be installed individually on each system.

OK, that's great, but I want this as a feature of my website - I want all my Flash videos to appear with a speed control for all users.  To date, I'd been unable to find any way to do this - no one I've spoken with seems to know how to write code for Flash Player that will permit a speed control.  I'm told it's currently not possible.  

Then I came upon Bloggingheads.tv.  Bloggingheads.tv includes a Flash-based player (derived from the JW Media Player 3.2)  that has a "1.4x" button that bumps up the playback speed -- perfectly intelligible, but much quicker playback for taking in a long talk in a jiffy.  They did the impossible!

I had to know how they did it, so I did some poking around. Turns out they didn't do the impossible, they did an end-run around it.  The playlist that their flash player reads for each video program references two media files.  Here's the relevant code snippet from the XSPF-format playlist:

<meta rel="alternate">

So, they created an alternate encoding of each video, one with the 1.4x timeline baked right in.  The player needed some modification to play this, but only so that the time, duration, and the location bar all showed an appropriately scaled value as this video played. After all, a 30 minute video encoded to play at 1.4x is actually only a 21 minute file, but the timeline still needs to show it like it's the 30 minute length of the original content.

When you switch from one speed to another while playing, the stream rebuffers and seeks to the same spot in the video, so there's just a momentary pause in playback switching from one stream to another.

It's a great workaround - although for my purposes (user-generated content, thousands of contributors) I'd still prefer a player-based way to do it so it can apply equally to video from all sources without requiring added backed processing.  Still...this is the only solution I've ever seen to this issue a) for Flash video, and b) not requiring an additional plugin.

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These features are really cool.
Thank you very much for the codes.

Thank you very much for given this informative article!


I'm the Dir. of business Development at Enounce.

We are now able to provide this functionality for websites. Also the user can now be using the Mac OS and a mulitude of browsers...
please email me to view the demo software. tstoker@enounce.com

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