Video Compression (Part 4 of 4)
Using Final Cut Pro and the Sorenson Video Codec
to Prepare QuickTime Video for Web Distribution

By Richard Lainhart


Then I enabled and set a media key for the Sorenson track. Sorenson has the ability to disable a video track from playing unless the viewer enters in a password, or media key. The media key needs to be entered in the QuickTime settings control panel on the user's machine, and does not get attached to the movie file. In other words, students buying a lesson will also get a media key they will have to enter before they can see the clip. Simply copying the clip to another system doesn't copy the key, so it has to be re-entered on the new system before the track can play. With luck, this will help cut down on the inevitable piracy that Jordan will be subject to. I chose "key!wiz" as the media key.

I then enabled Sorenson's Variable Bit Rate, or VBR, encoding. VBR is a feature of the Sorenson Developer edition, which is a $500 upgrade to the basic Sorenson codec included with all versions of QuickTime. VBR dramatically improves the quality of the compressed video, and is well worth the price if you're trying to get the best quality video. VBR encoding takes twice as long as regular Sorenson encoding, however, which is worth knowing because Sorenson is already a highly asymmetric codec - it takes much longer to compress than to decompress. VBR takes twice as long because the codec first does a complete analysis pass of your clip, marking the areas in the footage where more motion or noise occurs for more compression later on. The codec then varies the data rate from frame to frame to optimize compression in the problem areas and reduce the image degradation caused by the compression. The result is video that looks significantly better than non-VBR encoding, at the expense of time - Jordan's 4-minute video took over 14 hours to compress on the 400 MHz PowerBook, which is no slouch in the rendering department.

And that was it. A clip that had been more than 900MB ended up at less than 9MB, and it looks surprisingly good. If you'd like to see the results for yourself, you can download Jordan's video here by command clicking the Lesson 1link. Just remember that you have to enter the media key before you can see the video track. To enter the media key, open your QuickTime Settings control panel and choose Media Key from the popup menu. Click Add..., and in the dialog box that opens, type "SorensonVideo" (no spaces, and without the quotation marks) in the Category field. Then type "key!wiz" (without the quotes) in the Key field. Click OK, and close QuickTime settings. You should now be able to see the video. If not, make sure you typed in the Category and Key text exactly as shown.

Richard Lainhart ([email protected]) is a digital artisan who works with sonic and visual data. He's played vibes in a swing band; performed in public some 2000 times; composed music for film, television, CD-ROMs, and the Web; released recordings of his own music on the Periodic Music, Vacant Lot, and XI Records labels; engineered audio for recordings and live sound; written thirteen manuals for music and video hardware and software; served as technical director at a music software company; created 2D and 3D imagery and animation for print, broadcast, CD-ROMs, and the Web; served as contributing editor with Interactivity magazine; trained New York City-based digital media professionals in programs like Electric Image, After Effects, Premiere, Commotion, and Final Cut Pro; and contributed to books on digital media techniques published by IDG and Peachpit Press. Currently, he is Digital Media Specialist with Novaworks Computer Systems in New York City, an Adobe Certified Expert in After Effects, an occasional demo artist for Adobe Systems, and co-host of the official New York City After Effects User Group (http://www.otownmedia.com/nycaesig). His animation "A Haiku Setting" was recently accepted for the ResFest touring digital film festival. You can find it and samples of his music and digital artworks at his website, http://www.otownmedia.com.

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