1.3 What's the quality of DVD-Video?
Description
This article is from the DVD Formats FAQ, by jtfrog@usa.net (Jim Taylor) with numerous contributions by others.
1.3 What's the quality of DVD-Video?
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 (see 2.8.). However, quality depends on
many production factors. As compression experience and technology improves
we will see increasing quality, but as production costs decrease we will
also see more shoddily produced discs. A few low-budget DVDs will even use
MPEG-1 encoding (which is no better than VHS) instead of higher-quality
MPEG-2.
DVD video is usually encoded from digital studio master tapes to MPEG-2
format. The encoding process uses lossy compression that removes redundant
information (such as areas 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 visual flaws, depending on the processing quality and amount of
compression. At average rates of 3.5 Mbps (million bits/second),
compression artifacts may be occasionally noticeable. Higher data rates can
result in higher quality, with almost no perceptible difference from the
master at rates above 6 Mbps. As MPEG compression technology improves,
better quality is being achieved at lower rates.
Video from DVD sometimes contains visible artifacts such as color banding,
blurriness, blockiness, fuzzy dots, shimmering, missing detail, and even
effects such as a face that "floats" behind the rest of the moving picture.
It's important to understand that the term "artifact" refers to anything
that was not originally present in the picture. Artifacts are sometimes
caused by poor MPEG encoding, but artifacts are more often caused by a
poorly adjusted TV, bad cables, electrical interference, sloppy digital
noise reduction, improper picture enhancement, poor film-to-video transfer,
film grain, player faults, disc read errors, etc. Most DVDs exhibit few
visible MPEG compression artifacts on a properly configured system.. If you
think otherwise, you are misinterpreting what you see.
Some early DVD demos were not very good, but this is simply an indication
of how bad DVD can be if not properly processed and correctly reproduced.
Many demo discs were rushed through the encoding process in order to be
distributed as quickly as possible. Contrary to common opinion, and as
stupid as it may seem, these demos were not carefully "tweaked" to show DVD
at its best. In-store demos should be viewed with a grain of salt, since
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. Many DVD players
output video with a black-level setup of 0 IRE (Japanese standard) rather
than 7.5 IRE (US standard). On TVs that are not properly adjusted this can
cause some blotchiness in dark scenes. DVD video has exceptional color
fidelity, so muddy or washed-out colors are almost always a problem in the
display (or the original source), not in the DVD player or disc.
DVD audio quality is superb. DVD includes the option of PCM (pulse code
modulation) digital audio with sampling sizes and rates higher than audio
CD. Alternatively, audio for most movies is stored as discrete,
multi-channel surround sound using Dolby Digital or DTS audio compression
similar to the digital surround sound formats used in theaters. As with
video, audio quality depends on how well the processing and encoding was
done. In spite of compression, Dolby Digital and DTS can be close to or
better than CD quality.
The final assessment of DVD quality is in the hands of consumers. Most
viewers consistently rate it better than laserdisc, but 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 and the
level of quality delivered by the playback system.
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