Cobalt Digital COMPASS 9064 Up_Down_Cross Converter - Manual (Page 15)

9064-OM (V4.1) 9064 PRODUCT MANUAL 1-11
Introduction
9064 Functional Description
3-2 Pulldown Conversion and Considerations
Figure 1-3 depicts the 3-2 pulldown process used for conversions between
progressive film video formats and interlaced video formats. (Although the
term “3-2” is used here per convention, it is more accurately described as 2-3
per the diagram here and SMPTE definitions which stipulate that first film
frame
A be represented exclusively by 2 fields from the same frame). As
shown in Figure 1-3, the term 2-3 is derived from the pattern, or cadence, in
which four consecutive film video frames are converted into five consecutive
interlaced video frames (i.e., 10 interlaced video fields). Odd and even inter-
laced fields are denoted in Figure 1-3 by “
O
” and “
E
” (for example, “ A
O
” and
“ A
E
”). Note the considerations described in Figure 1-3 for converting to film
rates.
Figure 1-3 3-2 Pulldown and Reverse Pulldown
3-2 Pulldown
(From 1080p 24 To 1080i 60)
A B C D
A
O
A
E
B
O
B
E
B
O
C
E
C
O
D
E
D
O
D
E
3 2 3 2
A B C D
A
O
A
E
[1
O
1
E
]
B
O
B
E
[2
O
2
E
]
C
O
C
E
[4
O
3
E
]
D
O
D
E
[5
O
5
E
]
3-2 Reverse Pulldown
From 1080i 60 To 1080p 24
X X
1080p 24
1080i 60
1080i 60
1080p 24
“ 3 ” portions consist of three consecutive interlaced fields sourced from the
same film frame distributed across three consecutive interlaced fields.
“ 2 ” portions consist of two consecutive interlaced fields sourced from the same film
frame. The first film frame and first video frame are unique as a set in that their
contents are mutually and exclusively related to each other.
1 2 3 4 5
Using reverse pulldown, each film video frame is constructed from 2 interlaced fields with odd and even fields selected
as shown. The conversion pattern shown reverses the pulldown, thereby restoring the original signal.
Note: If the original interlaced material does not have the cadence described here, the conversion reverts to standard
de-interlacing. While this video can be converted to film rates, the resulting image motion will lack smoothness.
Therefore, make certain interlaced video is appropriately constructed for reverse pulldown when converting video to film
rates. Similarly, formats using a 30/29.97 Hz progressive frame rate can be converted to a 24/23.98 Hz progressive
frame rate, however some image motion irregularity will appear in the converted output.
A B C D
A
O
A
E
B
O
B
E
B
O
C
E
C
O
D
E
D
O
D
E
3 2 3 2
A B C D
A
O
A
E
[1
O
1
E
]
B
O
B
E
[2
O
2
E
]
C
O
C
E
[4
O
3
E
]
D
O
D
E
[5
O
5
E
]
X X
1 2 3 4 5