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

Remember last time when I mentioned that your "two-hour" DVD was actually just a storage disc with a 4.7GB (or 4.38GB if you're using computer terms) capacity?

Like you, I never questioned it. I'd record two 60-minute television shows and they'd go straight to DVD. When it was done, I'd turn the disc over to the pink side and see that the entire pink surface had been written to, from near the hub to outside by the edge. Just the way it was supposed to be.

Then I discovered video editing.

It wasn't that I wanted to slave over videos. That was for the football dads who yearned to beam over their progeny on the gridiron. I just didn't want commercials intruding on my television viewing. I found that when I extracted the unsightly distractions, the one-hour TV show turned into about a 43-minute extravaganza. Still, I put two on a disc. After all, that was 86 minutes — with only 34 minutes of the possible 120 remaining unfilled. There wasn't enough time left on the disc to squeeze in a third.

Time left on the disc?

It was then that someone wiser (at least about video editing) mentioned the words "video bit rate." Bit rate (or data rate) is the same in video as it is in audio: the number of bits per second recorded for the project. The more bits, the better the quality, Of course, I wanted great quality for my TV show recordings so I didn't immediately see how that was relevant. I wasn't going to suffer through the Super Long VHS blues any more. This was DVD!

After a little more research, I figured out that there was DVD the video quality and then there was DVD the disc and most of the world was somewhere in between.

I noticed that my TV shows were being recorded at 8000K bits per second. Technically that's DVD quality so I was doing well, right? Well, no. TV signals are broadcast somewhere around 2000K bits per second. (Maybe even a little less if you live in a deprived area like New York,) There I was, recording a 2000kbs signal at 8000kbs and the sorry truth is that while you can lower video quality by playing with the bit rate of an existing signal, you can't increase the quality by raising it. I was wasting at least 6000kbs of recording space. Those wasted bits added bulk to the file.

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