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Add Blackman-Harris window function and create go.mod file #27

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Add Blackman-Harris window function and create go.mod file #27

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ceb438e
Add go.mod file
rohansatapathy Oct 9, 2023
00cc865
Add Blackman-Harris window function
rohansatapathy Oct 9, 2023
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3 changes: 3 additions & 0 deletions go.mod
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
module github.com/mjibson/go-dsp

go 1.21.1
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Adding this file would definitely need to be in a separate PR. And since this repo doesn't have any tests, I'm not inclined to do that because I'm worried about unknown breakage. Also it should be the lowest supported go version, not the highest. In summary this change would need:

  • separate PR
  • running go test in a github action
  • minimum supported go version

19 changes: 19 additions & 0 deletions window/window.go
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Expand Up @@ -150,3 +150,22 @@ func Blackman(L int) []float64 {
}
return r
}

// BlackmanHarris returns an L-point Blackman-Harris window
// Reference: https://www.mathworks.com/help/signal/ref/blackmanharris.html
func BlackmanHarris(L int) []float64 {
r := make([]float64, L)
if L == 1 {
r[0] = 1
} else {
N := L - 1
for n := 0; n <= N; n++ {
const term0 = 0.35875
term1 := -0.48829 * math.Cos(2*math.Pi*float64(n)/float64(N))
term2 := 0.14128 * math.Cos(4*math.Pi*float64(n)/float64(N))
term3 := -0.01168 * math.Cos(6*math.Pi*float64(n)/float64(N))
r[n] = term0 + term1 + term2 + term3
}
}
return r
}
21 changes: 15 additions & 6 deletions window/window_test.go
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Expand Up @@ -23,12 +23,13 @@ import (
)

type windowTest struct {
in int
hamming []float64
hann []float64
bartlett []float64
flatTop []float64
blackman []float64
in int
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This has not been fmt'd.

hamming []float64
hann []float64
bartlett []float64
flatTop []float64
blackman []float64
blackmanHarris []float64
}

var windowTests = []windowTest{
Expand All @@ -39,6 +40,7 @@ var windowTests = []windowTest{
[]float64{1},
[]float64{1},
[]float64{1},
[]float64{1},
},
{
5,
Expand All @@ -47,6 +49,7 @@ var windowTests = []windowTest{
[]float64{0, 0.5, 1, 0.5, 0},
[]float64{-0.0004210510000000013, -0.05473684000000003, 1, -0.05473684000000003, -0.0004210510000000013},
[]float64{0, 0.34, 1, 0.34, 0},
[]float64{0.00006, 0.21747, 1, 0.21747, 0.00006},
},
{
10,
Expand All @@ -55,6 +58,7 @@ var windowTests = []windowTest{
[]float64{0, 0.222222222222222, 0.444444444444444, 0.666666666666667, 0.888888888888889, 0.888888888888889, 0.666666666666667, 0.444444444444444, 0.222222222222222, 0},
[]float64{-0.000421051000000, -0.020172031509486, -0.070199042063189, 0.198210530000000, 0.862476344072674, 0.862476344072674, 0.198210530000000, -0.070199042063189, -0.020172031509486, -0.000421051000000},
[]float64{0, 0.0508696327, 0.258000502, 0.63, 0.951129866, 0.951129866, 0.63, 0.258000502, 0.0508696327, 0},
[]float64{0.00006, 0.01507, 0.14704, 0.52057, 0.93166, 0.93166, 0.52057, 0.14704, 0.01507, 0.00006},
},
}

Expand Down Expand Up @@ -90,5 +94,10 @@ func TestWindowFunctions(t *testing.T) {
if !dsputils.PrettyClose(o, v.blackman) {
t.Error("blackman error\ninput:", v.in, "\noutput:", o, "\nexpected:", v.blackman)
}

o = BlackmanHarris(v.in)
if !dsputils.PrettyClose(o, v.blackmanHarris) {
t.Error("blackmanHarris error\ninput:", v.in, "\noutput:", o, "\nexpected:", v.blackmanHarris)
}
}
}