Median filters are nonlinear rank-order filters based on replacing
each element of the source vector with the median value, taken over the fixed
neighborhood (mask) of the processed element. These filters are extensively used in
image and signal processing applications. Median filtering removes impulsive noise,
while keeping the signal blurring to the minimum. Typically mask size (or window width)
is set to odd value which ensures simple function implementation and low output signal
bias. You can use an even mask size in function calls as well, but internally it will be
changed to odd by subtracting 1.
Another specific feature of the median filter implementation in Intel
IPP is that elements outside the source vector, which are needed to determine the median
value for “border” elements,
are located in a delay line. If the
delay line is absent, then they are set to be equal to the corresponding edge
element of the source vector.