Sony DVP-NS999ES - Manual (Page 47)

ES Series DVD-Video/CD/SA-CD Players; Version 3.0 Page 47
expect, DVD stores video footage in its native 60i form. But you might be
surprised to learn that most DVDs shot on film or 24P video store the images at
the native rate of 24 frames per second!
Like material shot on conventional, interlaced video, the typical DVD shot
on film is encoded from 60i videotape. But in the DVD authoring process, logic
circuits in the majority of high-quality MPEG encoders detect the telltale pattern
of 3-2-3-2 in the incoming video fields, the so-called 3-2 cadence. Since
repeated fields would waste precious disc space, the DVD eliminates them and
replaces them with First Field Repeat Flags (FFRFs) that tell the player which
fields to repeat. The remaining fields are reassembled back into their original
frames and encoded onto the DVD in progressive scan at 480/24P. This system
is 20% more space-efficient than 60i. It's an important advantage because it
enables DVDs to hold films that are 20% longer. Or DVDs can encode each
frame with 20% more bits, for even better picture quality.
The DVD stores film-originated material at 24P—the same rate as the
original film. First Field Repeat Flags (FFRFs) mark the 3-2 cadence.
The DVD player then performs its own 3-2 pulldown to output images at
60i.