Chapter 1

48 Everything You Ever Wanted to Know About DVD
and motion vectors may no longer be available to help the deinterlacer
determine the original format and cadence. (Some internal chips
receive the repeat_first_field and top_field_first flags passed from the
decoder, but not the progressive_scan flag.)
• External Analog video from the DVD player is passed to a separate
deinterlacer (line multiplier) or to a display with a built-in deinterlacer.
In this case, the video quality is slightly degraded from being converted
to analog, back to digital, and often back again to analog. However,
for high-end projection systems, a separate line multiplier (which
scales the video and interpolates to a variety of scanning rates) may
achieve the best results.
Most progressive DVD players use an internal deinterlacing chip usually
from Genesis/Faroudja. The Princeton PVD-5000 uses a Sigma Designs
decoder with integrated deinterlacing, while the JVC XV-D723GD uses a
custom decoder with integrated deinterlacing. Toshiba’s “Super Digital Progressive”
players and the Panasonic HD-1000 use 4:4:4 chroma oversampling,
which provides a slight quality boost from DVD’s native 4:2:0 format.
Add-on internal deinterlacers such as the Cinematrix and MSB Progressive
Plus are available to convert existing players to progressive-scan output.
Faroudja, Silicon Image (DVDO), and Videon (Omega) line multipliers are
examples of external deinterlacers.
A progressive DVD player has to determine whether the video should be
line-doubled or reinterleaved. When reinterleaving film-source video, the
player also has to deal with the difference between the film frame rate
(24 Hz) and the TV frame rate (30 Hz). Because the 2-3 pulldown trick can’t
be used to spread film frames across video fields, worse motion artifacts
occur than with interleaved video. However, the increase in resolvable detail
more than makes up for it. Advanced progressive players such as the
Princeton PVD-5000 and DVD computers can get around the problem by
displaying at multiples of 24 Hz, such as 72, 96, and so on.
A progressive player also has to deal with problems such as video that
doesn’t have clean cadence (such as when it’s edited after being converted
to interlaced video, when bad fields are removed during encoding, when
the video is speed-shifted to match the audio track, and so on). Another
problem is that many DVDs are encoded with incorrect MPEG-2 flags, so
the reinterleaver has to recognize and deal with pathological cases. In some
instances, it’s practically impossible to determine if a sequence is 30-frame
interlaced video or 30-frame progressive video. For example, the documentary
on Apollo 13 is interlaced-video-encoded as if it were progressive.
Other examples of improper encoding are Titanic, Austin Powers, Fargo,
More Tales of the City, the Galaxy Quest theatrical trailer, and The Big
Lebowski making-of featurette.