Altera Video and Image Processing Suite - Manual (Page 162)

Bob with Scanline Duplication
The bob with scanline duplication algorithm is the simplest and cheapest in terms of logic.
The bob with scanline duplication algorithm is the simplest and cheapest in terms of logic. Output frames
are produced by simply repeating every line in the current field twice. The function uses only the current
field, therefore if the output frame rate is the same as the input frame rate, the function discards half of the
input fields.
Bob with Scanline Interpolation
The bob with scanline interpolation algorithm has a slightly higher logic cost than bob with scanline
duplication but offers significantly better quality.
Output frames are produced by filling in the missing lines from the current field with the linear interpola‐
tion of the lines above and below them. At the top of an F1 field or the bottom of an F0 field there is only
one line available so it is just duplicated. The function only uses the current field, therefore if the output
frame rate is the same as the input frame rate, the function discards half of the input fields.
Weave
Weave deinterlacing creates an output frame by filling all of the missing lines in the current field with
lines from the previous field.
This option gives good results for still parts of an image but unpleasant artefacts in moving parts. The
weave algorithm requires external memory, so either double or triple-buffering must be selected. This
makes it significantly more expensive in logic elements and external RAM bandwidth than either of the
bob algorithms, if external buffering is not otherwise required.
The results of the weave algorithm can sometimes be perfect, in the instance where pairs of interlaced
fields have been created from original progressive frames. Weave simply stitches the frames back together
and the results are the same as the original, as long as output frame rate equal to input frame rate is
selected and the correct pairs of fields are put together. Usually progressive sources split each frame into a
pair consisting of an F0 field followed by an F1 field, so selecting F1 to be the current field often yields the
best results
Motion-Adaptive
Motion-adaptive algorithm is the most sophisticated of the algorithms provided but also the most
expensive, both in terms of logic area and external memory bandwidth requirement.
This algorithm avoids the weaknesses of bob and weave algorithms by using a form of bob deinterlacing
for moving areas of the image and weave style deinterlacing for still areas.
Select the Motion bleed algorithm to prevent the motion value from falling too fast at a specific pixel
position. If the motion computed from the current and the previous pixels is higher than the stored
motion value, the stored motion value is irrelevant and the function uses the computed motion in the
blending algorithm, which becomes the next stored motion value. However, if the computed motion value
is lower than the stored motion value, the following actions occur:
• The blending algorithm uses the stored motion value.
• The next stored motion value is an average of the computed motion and of the stored motion.
This computed motion means that the motion that the blending algorithm uses climbs up immediately,
but takes about four or five frames to stabilize. The motion-adaptive algorithm fills in the rows that are
UG-VIPSUITE
2015.05.04
Bob with Scanline Duplication 12-3
Deinterlacing IP Cores Altera Corporation
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