144 lines
3.0 KiB
Go
144 lines
3.0 KiB
Go
package extractfreq
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import (
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"fmt"
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"log"
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"math"
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"math/cmplx"
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"git.crumpington.com/public/jlaudio/lib/flac"
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"gonum.org/v1/gonum/fourier"
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"gonum.org/v1/plot"
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"gonum.org/v1/plot/plotter"
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"gonum.org/v1/plot/plotutil"
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"gonum.org/v1/plot/vg"
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)
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// Steps:
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//
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// * Create amplitude spectrum (abs of real FFT).
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// * Multiply by A-weight curve
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// * Find peaks
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// * Sort peaks by amplitude
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// * Use strongest peak to estimate fFundamental?
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// *
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func PlotFFT(path string, nSamples int, fFundamental float64) {
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L, R, err := flac.Load(path)
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if err != nil {
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panic(err)
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}
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if nSamples < len(L) {
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nSamples = len(L)
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}
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data := make([]float64, nSamples)
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for i := range data {
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data[i] = float64(L[i]) + float64(R[i])
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}
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// Make initial fft.
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fft := fourier.NewFFT(nSamples)
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cCoeffs := fft.Coefficients(nil, data)
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amps := make([]float64, len(cCoeffs))
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freqs := make([]float64, len(cCoeffs))
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for i := range freqs {
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freqs[i] = fft.Freq(i) * 48000
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amps[i] = cmplx.Abs(cCoeffs[i])
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}
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// Trim to frequencies of interest.
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deltaF := freqs[1] - freqs[0]
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idx0 := int(20 / deltaF)
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idx1 := int(16000 / deltaF)
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freqs = freqs[idx0:idx1]
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amps = amps[idx0:idx1]
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// Multiply by A-weight function.
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for i := range amps {
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amps[i] *= AWeight(freqs[i])
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}
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// Find peaks.
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dFreq := freqs[1] - freqs[0]
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halfWinSize := int(math.Round((fFundamental / dFreq) / 3))
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peakInds, peakAmps := getPeaks(halfWinSize, amps)
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peakInds, peakAmps = sortPeaks(peakInds, peakAmps)
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p, err := plot.New()
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if err != nil {
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panic(err)
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}
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fMin := float64(20)
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fMax := float64(16000)
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log.Printf("Making points...")
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pts := make(plotter.XYs, 0, len(amps))
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for i := range amps {
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if freqs[i] > fMin && freqs[i] < fMax {
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pts = append(pts, plotter.XY{
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X: freqs[i],
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Y: amps[i],
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})
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}
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}
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pts2 := make(plotter.XYs, 0, len(amps))
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for i := range peakInds {
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if freqs[peakInds[i]] > fMin && freqs[peakInds[i]] < fMax {
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pts2 = append(pts2, plotter.XY{
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X: freqs[peakInds[i]],
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Y: peakAmps[i],
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})
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}
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}
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log.Printf("Plotting...")
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if err = plotutil.AddScatters(p, "fft", pts, "max", pts2); err != nil {
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panic(err)
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}
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p.Add(plotter.NewGrid())
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log.Printf("Saving...")
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if err := p.Save(16*vg.Inch, 8*vg.Inch, "fft.png"); err != nil {
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panic(err)
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}
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for i, idx := range peakInds {
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//amp := peakAmps[i]
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// Make window.
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ampsWin := amps[idx-halfWinSize : idx+halfWinSize]
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freqWin := freqs[idx-halfWinSize : idx+halfWinSize]
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log.Printf("Making points...")
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pts := make(plotter.XYs, 0, 2*halfWinSize)
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for i := range ampsWin {
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pts = append(pts, plotter.XY{
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X: freqWin[i],
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Y: ampsWin[i],
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})
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}
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log.Printf("Plotting...")
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p, err := plot.New()
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if err != nil {
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panic(err)
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}
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if err = plotutil.AddLines(p, "fft", pts); err != nil {
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panic(err)
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}
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//p.Y.Scale = plot.LogScale{}
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//p.X.Scale = plot.LogScale{}
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log.Printf("Saving...")
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filename := fmt.Sprintf("plot-%03d.png", i)
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if err := p.Save(8*vg.Inch, 8*vg.Inch, filename); err != nil {
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panic(err)
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}
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}
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}
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