DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

SMPTE RP 197, Film-to-Video
Transfer List.
SMPTE RP 201, Encoding Film
Transfer Information Using Vertical
Interval Time Code.
video fields, but the individual images are still intact.
The result of the naive framebuffer approach is shown
the right column: Spatial discontinuities are introduced
into two of the five fields. With conversion from 24 Hz
to 60 Hz, depending on the phase alignment of film
and video, either two or three discontinuities will be
evident to the viewer. With conversion from film at
exactly 24 Hz to video at 59.94 Hz, the discontinuities
will drift slowly down the screen.
Using a pair of buffers – double buffering – and synchronizing
the writing and reading of the buffers with the
start of the film and video frames, keeps each frame
intact and removes the spatial discontinuities. However,
the delays involved in this technique reintroduce
exactly the same temporal stutter as 2-3 pulldown!
Although 2-3 pulldown introduces a temporal artifact
into the video stream, acceptable motion portrayal is
obtained when the 2-3 video is displayed at video rate.
However, if the frame rate is altered a second time,
temporal artifacts of the two cascaded conversions may
become objectionable; this is especially true when the
image is displayed with a wide picture angle.
If transfer from film to video is carefully done, pictures
ending with timecode digits 0 or 5 are A-frames. Aside
from A-frame-locked timecode, there are no standards
that convey, along with a video signal, information
concerning film origination. Absent locked timecode,
the only way to detect 2-3 pulldown is to compare data
in successive, like fields: If two successive first fields
contain identical luma and chroma, within a certain
noise tolerance, and the repeat pattern follows the
characteristic 2-3 sequence, then the material can be
assumed to have originated from film. Once the original
film frames have been identified, conversion to the
ultimate display rate can be accomplished with minimal
introduction of motion artifacts. Identifying film frames
using this method is feasible for dedicated hardware,
but it is impractical for today’s desktop computers.
434 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES