[PATCH 1/2] Add Variance filter
Andy Green
andy at openmoko.com
Thu Dec 4 22:31:42 CET 2008
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Somebody in the thread at some point said:
| This filter is useful to reject clicks that are not reliable. We
| only care about what happens when we receive DOWN events for the fist
time.
| If this filter does not reject the first samples then it will change
| its internal state to "passed" and the remaining samples
| will be sent to the next filter in the chain.
|
| First we collect N samples, then then we sort them. We discard the
borders
| of the vector (with a window) and then compute the variance of the
remaining
| set. If the computed variance is bigger than a threshold, we reject
the click.
|
| The parameters of the filter are:
|
| * size
| * threshold /* maximum allowed variance */
| * window
|
| I'm using values I tuned by trial an error. I noticed we discard a lot
| of bugus clicks. In fact, it seems harder to get them now.
Thanks Nelson I sent these two on stable-tracking.
- -Andy
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