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Best Bits: Miracle Of The 2-Hour DVD Disc, Part 2

If you want to, you can put four hour-long TV programs on a DVD disc. Really. DVDs can't tell time. How are they going to know?
For example: A one hour and 6 minute video clip (you always add a little to the front and back in case of vagaries in your system clock or the network's) runs about 3.5GB at 8000kbs. (Notice how I'm subtly transitioning from talking about the time of these videos to talking about their size.) If you back the bit rate down to 3000kbs, you end up with a file that's about 1GB in size. And if you happen to tell your rendering software to use a variable bit rate with a defined maximum, it can get lower still.

For example again: I took that 1-hour-and-six-minute recorded video, stripped out the commercials, and ended up with about 43 minutes of raw video. When I told my editing software (Ulead VideoStudio 10 plus) to stitch those five or six clips (depending on how many commercial interruptions there were) back together, I also told it to use a variable bit rate with a 3000kbs cap. (That's still above TV's transmission rate so, in theory, I'm not degrading the quality of the video.) The resulting rendered video is about 900MB, which will vary a little, more or less, depending on the exact total length of the clips.

So. "Two-hour DVD"? I don't think so. Lets do some math. If you divide 4.38GB by 900MB the result (according to Excel) is 4.87. That means that 4.87 forty-three minute videos will fit on that disc. If we stick to the pure math, that equals 209.67 minutes or, roughly, 3.49 hours.

Wait a minute! Didn't we begin this exercise with 2-hour DVDs? And now I'm telling you that they'll hold 3-hours and 29 minutes of video? It's a miracle! All right, it's just math based on the byte capacity of the disc, not any artificially selected time associated with it.

Reality dictates that, currently, based on the video bit rate I'm using, I can comfortably fit four 43-minute videos (172 minutes) on my "120-minute" DVD disc. If I lowered the bit rate of the rendered videos just a little more, I could probably fit five videos, 215 minutes, on one. Considering how the price of single-layer DVD-R discs have plummeted over time, four is just fine by me. Your video mileage may vary — just don't ever call it as a 2-hour DVD again.

Bill O'Brien can be blamed for more than 2,000 articles on computers and technology topics. With his writing partner, Alice Hill, Bill co-authored "The Hard Edge," the longest-running (1992 to 2004) technology column penned by a techno duo. For more, go to www.technudge.com.