Controlling The 2:3 Pulldown; Figure 3-5: Timecode Referenced 2:3 Pulldown And Delay In Hd9155 - evertz HD9155 Series Instruction Manual

Model HD9155 Production Afterburner Manual
3.2.

CONTROLLING THE 2:3 PULLDOWN

When the input video to the HD9155 is 1080p/23.98sF, the HD9155 will insert 1 extra field every 4 to
create a 29.97 Fps output video. This process, known as 2:3 Pulldown can be controlled by one of 3
sources.
•
Video Timecode values being read from the RP188 ANC data packet encoded in the ancillary data
space of the incoming video. (often referred to as VITC but not to be confused by SMPTE 12M VITC)
•
LTC Timecode being read by the LTC reader
•
External 6 Hz Reference pulse applied to the Parallel I/O connector
If more than one source is present then the HD9155 uses the RP188 Time Code as the highest priority
and the 6 Hz input as the lowest priority. The preferred method of controlling 2:3 cadence is to use the
RP188 ANC timecode that will be read directly from the incoming video. (See Figure 3-1). If the user
wants to change the priority scheme of the HD9155 this can be accomplished using system parameters
(see chapter 5
To confirm the HD9155 2:3 reference source, turn on the Debug character generator window (using the
Window tab in the 9150 Configware™ software. Set the horizontal position to 11. You will see a display
on the HD9155 Character generator that looks something like the following:
REF: ANC 1 0 3
Consult section 6.4 for a more detailed description of how to use the debug character window and specific
information on the Pulldown Reference Source Window.
Figure 3-5 shows the relationship between the incoming 1080p/24sF video and the outgoing 525i/59.94
video, with the A frames of the output video correctly aligned to the incoming timecode. Then the A frames
will be aligned with the 0 frames of either the input LTC or input RP188 ANC video timecode.
Note that there is a 5 video frame (1/6
frame alignment of the output video. If you have the AES option installed (model HD9155-AES) the AES
audio outputs of the HD9155 will be delayed by an equivalent amount so that it is in time with the picture.
Otherwise you will have to provide an external delay for the audio.
1080p/24sF
:00
Time Code
0
1080p/23.98sF
A Frame Candidate
0 0
Frame
Buffer odd even
525i/59.94

Figure 3-5: Timecode Referenced 2:3 Pulldown and Delay in HD9155

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th
of a second) delay inside the HD9155 to allow for the correct A
:01 :02
1 2
1 1 2 2
odd even odd even odd
Revision 1.3
:03
3 4
A Frame Candidate
3 3 4 4
even odd even
0 0 1
odd even odd even
A Frame B Frame
1 1 2 2 3 3
odd even odd even odd
C Frame D Frame
OPERATION
3
even