Chapter 1

30 Everything You Ever Wanted to Know About DVD
A DVD recorder basically works like a VCR. It has a tuner and A/V inputs,
and it can be programmed to record shows. An important difference is that
you never have to rewind or fast forward. Recordings on a disc are instantly
accessible, usually from an onscreen menu. Note that DVD video recorders
can’t copy most DVD movie discs, which are protected.
Unfortunately, more than one recordable DVD format is available, and
they don’t all play together nicely. It’s nothing like the old VHS versus Betamax
battle, as many in the press would have you believe, but it is rather
confusing. See Chapter 4’s “What About Recordable DVDs: DVD-R, DVD-
RAM, DVD-RW, DVD�RW, and DVD�R?” to get more confused.
Don’t be further confused by DVD recordable drives (DVD burners) for
computers. These recorders can store data, but creating full-featured DVD-
Videos requires additional software to do video encoding (MPEG), audio
encoding (Dolby Digital, MPEG, or PCM), navigation and control data generation,
and so on (see Chapter 5, “DVD Production”).
What Happens If I Scratch the Disc? Aren’t Discs
Too Fragile to Be Rented?
Scratches may cause minor data errors that are easily corrected. That is,
data is stored on DVDs using powerful error-correction techniques that can
recover from even large scratches with no loss of data. A common misperception
is that a scratch will be worse on a DVD than on a CD because of
higher storage density and because video is heavily compressed. DVD data
density is physically four times that of CD-ROM, so it’s true that a scratch will
affect more data, but DVD error correction is at least 10 times better than
CD-ROM error correction and more than makes up for the density increase.
It’s also important to realize that MPEG-2 and Dolby Digital compression are
partly based on the removal or reduction of imperceptible information, so
decompression doesn’t expand the data as much as might be assumed.
Major scratches may cause uncorrectable errors that will produce an
input/output (I/O) error on a computer or show up as a momentary glitch in
the DVD-Video picture. Paradoxically, sometimes the smallest scratches
can cause the worst errors (because of the particular orientation and refraction
of the scratch). Many schemes can conceal errors in MPEG video,
which may be used in future players. See the later section “How Should I
Clean and Care for DVDs?” for more information.
The industry’s DVD computer advisory group specifically requested no
mandatory caddies or other protective carriers. Consider that laserdiscs,
music CDs, and CD-ROMs are likewise subject to scratches, but many
video stores and libraries rent them. Most reports of rental disc perfor-