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File Formats and Translation:
Although the DV Stream format has some compression to it, its not nearly
as compressed as many other video file formats, meaning the result is a
fairly large file. In raw DV files, each minute of video takes more than
220MB of disk space, or about 13.2GB per 10 minutes of video. That’s a
lot of space, and, what’s more, it’s utterly impractical for just about any sort
of playback or transfer aside from editing and moving from tape to hard
disk and back again.
To use the video for different purposes, then, you’ll likely translate it into
another file format. Those formats can range from international standards
such as the MPEG standards, to proprietary formats such as Apple’s
QuickTime or Microsoft’s AVI or Windows Media formats. In many cases,
that format is designed specifically for the targeted medium—if you’re
creating a DVD movie (or a video CD) from your DV Stream files, you’ll
edit them together and export them from your video editing software into
an MPEG-2 file, a file with the standard compression and format for
burning onto a DVD that can be played back in consumer equipment.
MPEG-2, by way of comparison, requires about 2GB per hour, which
means the files are a sixth the size of DV Stream files—that’s part of what
makes them work well for DVDs.
MPEG stands for the Motion Picture Experts Group (http://mpeg.telecomitalialab.com/),
which is a working group, creates audio and video compression standards. Along with the MPEG-1
(compression that works for CD or hard disk storage), MPEG-2 (DVD-quality compression) and MPEG-4
(online streaming compression) video standards, MPEG also created the MPEG Audio Layer 3 (MP3)
standard that’s popular for music storage and online transfer.
Even so, the same file would be pretty close to useless for regular CDs
or for hard-disk based movies—in that case, you’d choose an even more
compressible format such as the MPEG-1 format, which requires about 1GB per hour. MPEG-1 is an older format that’s less sophisticated, so you
might begin to branch out to more proprietary formats such as theWindows
Media format that’s used on MicrosoftWindows platforms or the QuickTime
format used primarily on Macs, both of which can be used with various codecs
(compressor/decompressors) to change their data rates and ultimate file
sizes. (Both formats can also, in various capacities and with some limitations,
be used on the opposite platform—you can play some Windows Media
feeds on Macs and you can use QuickTime technology in Windows if the
correct applications and support files are installed.) The more compressed
a file (and the less sophisticated the codec), the less true it is to the original
DV Stream file, perhaps introducing artifacts, color shifts, or blurred and
blocky motion sequences.
At the other end of the spectrum are files small enough to be transferred
or streamed over the Internet. These are highly compressed QuickTime or
Windows Media movies; Real Media movies (www.real.com) for playback
in the RealOne line of players (a popular but proprietary approach); or the
MPEG-4 standard, which emerged relatively recently as a contender on
the Internet streaming front. Using these formats, you can place a relatively
small video file on a server and make it available to others over the Internet,
or you can attach it to an e-mail, place it on a Zip disk, or otherwise make
it accessible. The movie will probably be smaller in appearance and of
much lower quality than the DV Stream file, but those technologies are
getting better all the time, so that even relatively large movies can be
streamed over an Internet broadband to a user with great results.
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