Rockbox mail archiveSubject: Re: DSP: low pass filter
Re: DSP: low pass filter
From: Tomas <tomas_at_salfischberger.nl>
Date: Mon, 15 Aug 2005 21:54:00 +0200
Well... following my calculations and Dave's suggestion I have just used
a 128 samples moving average, and it works great.
My next problem is how to do continuous backlight dimming (not constant)
but I think that's something for Miika...
At the moment I have a flashing remote, activating the backlight on
peaks (predefined value) on the bass channel.
>>Thanks, we got to the point that averaging is enough on IRC tonight
>>too... but we had no way to calculate how many samples to average...
>I suggest using an IIR filter instead of FIR. You need way less past samples
>for each step. The most simple IIR filter is like a charge/discharge (first
>order lowpass): e.g. take 90% of your "charge", 10% of the new value, to get
>the new charge. Play with the parameters, generalized it's n and (1-n). If
>you use less of the current, the thing becomes slower, lower corner
>Power of two gives the benefit of using shift instead of multiply. Use >16
>bit for the charge.
Received on 2005-08-15