Chris@25: 
Chris@25: Decimation
Chris@25: ==========
Chris@25: 
Chris@25: The aim of this little project is to compare a few different methods
Chris@25: of signal decimation for relative speed and quality. "Decimation"
Chris@27: refers here to downsampling a signal by a power-of-two factor.
Chris@25: 
Chris@25: The principle is to use a low-pass filter to reduce the bandwidth of
Chris@25: the signal to below the Nyquist frequency at the target sample rate
Chris@25: (i.e. with the maximum frequency content being below the original rate
Chris@25: divided by twice N, for a decimation factor N) and then to pick every
Chris@25: Nth sample.
Chris@25: 
Chris@25: This is simple enough, but we have a few different implementations
Chris@25: available with different quality and performance tradeoffs. Here we
Chris@25: compare:
Chris@25: 
Chris@25:  * "decimate": the Decimator implementation in the qm-dsp library,
Chris@25:    which uses an 8-tap IIR lowpass filter;
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Chris@25:  * "resample_hq", "resample_mq", "resample_lq": the Resampler
Chris@25:    implementation in the qm-dsp library, which uses a lengthy
Chris@25:    Kaiser-windowed sinc filter, at three different quality settings;
Chris@25:    
Chris@25:  * "src": the sndfile-resample program which uses libsamplerate, a
Chris@25:    well trusted resampler also using a Kaiser-windowed sinc
Chris@25:    implementation, at its default quality setting;
Chris@25: 
Chris@25:  * "zoh": the sndfile-resample zero-order hold resampler, which just
Chris@25:    takes every Nth sample without any filtering, serving as a
Chris@25:    baseline.
Chris@25: 
Chris@25: Run "make" (caution: only tested on Linux with GNU make and bash) to
Chris@25: build and run the tests.
Chris@25: 
Chris@25: Author: Chris Cannam (cannam@all-day-breakfast.com)
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