Quality of DVD-Video

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DVD has the capability to produce near-studio-quality video and
better-than-CD-quality audio. DVD
is vastly superior to videotape and generally better than laserdisc.
However, quality
depends on many production factors. Until compression experience and
technology improves we will
occasionally see DVDs that are inferior to laserdiscs. Also, since large
amounts of video have already
been encoded for Video CD using MPEG-1, a few low-budget DVDs will use that
format (which is
no better than VHS) instead of higher-quality MPEG-2 (See
Chapters 6 and  7)

DVD video is compressed from digital studio master tapes to MPEG-2 format.
This is a lossy
compression (see Chapter 7) which removes redundant information (such
as sections of the picture that don’t change)
and information that’s not readily perceptible by the human eye. The
resulting video, especially when
it is complex or changing quickly, may sometimes contain artifacts such
as blockiness, fuzziness,
and video noise depending on the processing quality and amount of compression
(Chapter 7). At average rates of
3.5 Mbps (million bits/second), artifacts may be occasionally noticeable.
Higher data rates result in
higher quality, with almost no perceptible difference from the original
master at rates above 6 Mbps.
As MPEG compression technology improves, better quality is being achieved at
lower rates.

Some DVD demos have visible artifacts such as color banding, blurriness,
shimmering, missing
detail, and even effects such as a face which floats behind the rest of
the moving picture. This is
sometimes caused by poor MPEG encoding, but is just as often caused by a
poorly adjusted TV or by
sloppy digital noise reduction prior to encoding. The Free Willy and Twister
excerpts on the
Panasonic demo disc are good examples of this. In any case, bad demos are
not an indication that
DVD quality is bad, since other demos show no artifacts or other problems.
Bad demos are simply an
indication of how bad DVD can be if not properly processed and correctly
reproduced. Early demos
were shown on prototype players based on prerelease hardware and firmware.
Many demo discs
were rushed through the encoding process in order to be distributed as
quickly as possible. Contrary
to popular opinion, and as stupid as it may seem, these demos are not
carefully tweaked to show
DVD at its best. Also, most salespeople are incapable of properly adjusting
a television set. Most TVs
have the sharpness set too high for the clarity of DVD. This exaggerates
high-frequency video and
causes distortion, just as the treble control set too high for a CD causes
it to sound harsh. DVD video
has exceptional color fidelity, so muddy or washed-out colors are almost
always a problem in the
display, not in the DVD player or disc.

DVD audio quality is excellent. One of DVD’s audio formats is LPCM (linear
pulse code modulation)
with sampling sizes and rates higher than audio CD. Alternately, audio for
most movies is stored as
discrete multi-channel surround sound using Dolby Digital or MPEG-2 audio
compression similar to
the surround sound formats used in theaters. As with video, audio quality
depends on how well the
encoding was done. Most audio on DVD will be in Dolby Digital format, which
is close to CD
quality.

The final assessment of DVD quality is in the hands of consumers. Most
initial reports consistently
rate it better than laserdisc. No one can guarantee the quality of DVD, just
as no one should dismiss it
based on demos or hearsay. In the end it’s a matter of individual
perception.

Next: What are the disadvantages
Up: DVD
Previous: What are the features
Dave Marshall

10/4/2001