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HDV Camcorders > HDV Camcorders - Pg. 103

That's not to say that iMovie actually imports MPEG-4 video the same way it imports MiniDV footage; it doesn't. But when you connect one of these 'corders to your Mac's USB jack, the memory card shows up on your screen as though it's a disk. Double- click it to reveal its contents, which include a folder with all your video recordings in it. You can bring them into iMovie by simply dragging their Finder icons into the Movie Track or Clips pane of the open iMovie window. Four Special Cases HDV Camcorders If Apple's marketing is to be believed, the big news in iMovie HD is the HD part. At its release, iMovie HD was by far the least expensive software capable of importing and editing video from high-defnition camcorders. (It's about $750 less expensive than the next contender.) power users' clinic HDV, Apple Intermediate Codec, and You If you've been merrily reading along, learning all kinds of new things about high-defnition video, one apparent contradiction in this chapter might already be bugging your subconscious. First you read that an HDV camcorder stores a full hour of high-defnition video on a 60-minute Mini-DV tape--a cassette designed to hold 60 minutes of standard-defni- tion video. And then you read that HDV video takes up three or four times as much hard drive space as standard DV. Which is it? Does HDV footage take up the same amount of disk space as standard DV, or does it take up much more? Answer: It takes up much more, unless it's massively com- pressed. That's the most amazing part of the circuitry in today's HDV consumer camcorders: it manages to compress all of that information in real time, so that it fts in the same amount of tape as standard DV. Your Mac, however, is not quite as dedicated a machine. Even the fastest Mac wouldn't be able to edit HDV footage in its original, super-compressed form. It'd be like: click to select a clip, wait; scroll to a later place in the clip, wait; hit the Space bar to play it, wait; and so on. So Apple did something very clever in iMovie HD: when it im- ports video from an HDV camcorder, it transcodes (converts) the signal into a much more lightly compressed format on your hard drive, using a new, virtually lossless compression scheme called the Apple Intermediate Codec (AIC). Once the footage is safely aboard your hard drive, you can edit it just as easily and quickly as you can regular DV video. When you export your fnished movie back to the HDV camcorder, iMovie reconverts it to the more compressed format that the camcorder expects. During both of these transfers of video--from the camcorder, and later back to the camcorder--it's the transcoding that takes so much time. That's why importing HDV video isn't a real-time process in iMovie HD. Now that you understand what transcoding is, here's a tip that exploits your new awareness. If, during importing, you click the Stop button to stop the tape, iMovie continues transcoding the video it's already stored temporarily on the hard drive, right up until it catches up with the spot on the tape where you stopped. (A progress dialog box appears on the screen during this conversion process.) But if you end the importing by clicking the Import button (to turn it off), iMovie stops right away. It throws away everything in its buffer, and keeps only what it has already transcoded. chapter4:camcordermeetsmac 103