Resample digital signal in C

Resample digital signal in C

Post by artau » Thu, 11 May 1995 04:00:00



Hello

I 'm looking for a programme source in C to resample a digital signal to
lower or higher frequencies (includinding the low pass filter for lower
frequencies). Do you know where i can find this ?

Thanks in advance.

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1. Please explain digital resampling

I want to perform a number of DSP operations on a signal.  The operations
require different sampling rates, so I need to split the incoming signal of
rate A into two signals of rate B and rate C.

My books explain how up- and downsampling by a factor N is done, when N is
0,1,2..

In my application I need to generate 6000 Hz and 6800Hz signals from a
signal that has to be acquired at >8400Hz and <19200Hz.  The lowest common
multiple of 6000 _and_ 6800 is 102000.  I obviously need a 102KHz signal to
generate 6000 and 6800 Hz signals by just leaving out samples (as suggested
by my books).

So I think that I could sample at 10200Hz, pad each sample byte with 9
0-bytes, run an interpolation filter on that and then leave out most of the
results to reach 6000 Hz and 6800 Hz.  This does not violate the up- and
downsampling chapter of my DSP book, but it looks ridiculous and very CPU
hungry.

I'm sure there is a better way to resample to rates that are not multiple
of the original rate or vice versa, isn't it?

PS:  I'm sorry if this is a beginner question.  I don't have access to a
     DSP course here in Germany.  My only sources of information are the
     internet and books (I always appreciate ISBN numbers of good DSP
     books - in Germany bookstores don't carry them so I can't just browse
     through the stores).

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