TYPE: CHOP
TITLE: Filter CHOP

This CHOP smoothes or sharpens the input channels. It filters by combining
each sample and a range of its neighbor samples to set the new value of that
sample. Each filter type uses its own weighting factors for the neighbor
samples. The Filter Width determines the number of neighbors to use.

This CHOP can filter motion and sound, but other CHOPs are more appropriate
for filtering sound (Pass Filter, Band EQ, Parametric EQ CHOPs).

This CHOP can filter data in time slice mode. Gaussian, Box, Sharpen, Edge 
Detect and Despike filters will delay the channel values by half the filter
width. Left Half Gaussian and Left Half box will not delay the channel values.

Parameters
    Type - There are 7 types of filters. See manual for pictures of shapes.
        Gaussian - This filter has a Gaussian (normal or "bell" curve)
                shape that smoothes the channel. It acts as a low pass
                filter. The wider the filter, the lower the cutoff
                frequency, resulting in smoother data. 
        Left Half Gaussian - This produces a lag on the channel. If the
                input channels represent values over time, this filter
                is seen as only using samples back in time from the
                current sample. For time-data, this is more realistic as
                you can't look ahead in time. It has a half-bell shape.
        Box - This filter is box-shaped, meaning that each neighbor
                sample it uses has the same weighting factor. It can
                produce unwanted steps in the output channel because
                the effect of the samples at the extremes of the filter
                don't fade out as the window slides over the samples.
                It low-pass filters data, similar to the Gaussian filter.
        Left Half Box - This filter produces a lag on the data, uses
                only samples back in time, and otherwise acts like a
                box filter.
        Edge Detect - This filter detects "edges", sharp changes in the
                input channels. It acts as a high pass filter. As the
                filter width is increased, more low frequencies are added.
        Sharpen - This filter sharpens all high frequencies. It is the
                sum of the edge detect result and the original data.
        De-spike - This filter removes "spikes" (samples more than `Spike
                Tolerance' above or below of the expected sample value).
                The filter width allows you to eliminate spikes that are
                several samples long. Wide filters will remove wide spikes
                (spikes of several samples) and small filters will only
                remove narrow spikes (one or two samples in length).
    Effect           - The extent to which the filter affects the      /effect
                       channel (0 - not at all, 1 - maximum effect). 
    Filter Width     - The amount of surrounding samples used in       /width
                       the calculation of the current sample. It
                       is expressed in Units (in the Common page).
    Spike Tolerance  - For the De-spike filter type, this is the       /spike
                       amount that a sample can differ from its
                       neighbours without being considered a spike.
    Number of Passes - The number of times the filter is applied       /passes
                       to the channel.

Local Variables
        C       - current channel index (0 to NC-1)
        NC      - total number of channels

See also: Limit, Pass Filter(pass)
