User guide

Appendix B: Choosing the Correct Deinterlacer B–5
Cadence Detection and Reverse Pulldown in the Deinterlacer II MegaCore Function—In Depth
January 2013 Altera Corporation Video and Image Processing Suite
User Guide
When the cadence detect component enters a lock state, the deinterlacer continuously
assembles a coherent frame from the incoming fields, by either weaving the current
incoming field with the previous one (shown as weave current in Figure B–7) or by
weaving the two past fields together (weave past), as shown in Figure B–7:
If the incoming video contains any cadenced video, you must enable the Cadence
detection and reverse pulldown option from the Behavior parameter in the
Parameter Settings tab. Then, select the cadence detection algorithm according to the
type of content you are expecting. If the incoming video will contain both 3:2 and 2:2
cadences, select 3:2 & 2:2 detector.
The cadence detection algorithms are also designed to be robust to false-lock
scenarios—for example, features on adjacent fields may trick other detection schemes
into detecting a cadence where there is none.
Figure B–7. Weave Current and Weave Past
3 3
3 4
4
5
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Cadence detection declares
telecine lock at this point (after the
field was processed)
Weave
current (4)
Normal
deinterlace
Scheduler behaviour
Normal
deinterlace
Normal
deinterlace
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(
4
)
The deinterlacer starts to use cadence
information to weave fields correctly
Normal deinterlacing
Inverse telecine deinterlacing
Weave
current (6)
Weave
past (5)
Weave
past (5)
Weave
current (5)
Weave
past (4)
Weave
past (3)