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NoiseCapture/src/commonMain/kotlin/org/noise_planet/noisecapture/signal/FFT.kt
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NoiseCapture/src/commonMain/kotlin/org/noise_planet/noisecapture/signal/fft.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,74 @@ | ||
| package org.noise_planet.noisecapture.signal | ||
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| import kotlin.math.PI | ||
| import kotlin.math.cos | ||
| import kotlin.math.pow | ||
| import kotlin.math.sin | ||
| import kotlin.math.log2 | ||
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| fun fft(length: Int, riArray: DoubleArray) { | ||
| val m = log2(length.toDouble()).toInt() | ||
| val n = (2.0.pow(m) + 0.5).toInt() | ||
| require(n <= riArray.size) | ||
| var wCos: Double | ||
| var wSin: Double | ||
| var uCos: Double | ||
| var uSin: Double | ||
| val n2 = n shr 1 | ||
| var l1 = n | ||
| var l2: Int | ||
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| for (l in 0 until m) { | ||
| l2 = l1 shr 1 | ||
| wCos = 1.0 | ||
| wSin = 0.0 | ||
| uCos = cos(PI / l2) | ||
| uSin = -sin(PI / l2) | ||
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| for (j in 0 until l2) { | ||
| for (i in j until n step l1) { | ||
| val ir = 2 * i | ||
| val ii = ir + 1 | ||
| val l22 = 2 * l2 | ||
| val sumRe = riArray[ir] + riArray[ir + l22] | ||
| val sumIm = riArray[ii] + riArray[ii + l22] | ||
| val diffRe = riArray[ir] - riArray[ir + l22] | ||
| val diffIm = riArray[ii] - riArray[ii + l22] | ||
| riArray[ir + l22] = diffRe * wCos - diffIm * wSin | ||
| riArray[ii + l22] = diffRe * wSin + diffIm * wCos | ||
| riArray[ir] = sumRe | ||
| riArray[ii] = sumIm | ||
| } | ||
| val w = wCos * uCos - wSin * uSin | ||
| wSin = wCos * uSin + wSin * uCos | ||
| wCos = w | ||
| } | ||
| l1 = l1 shr 1 | ||
| } | ||
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| var k: Int | ||
| var j = 0 | ||
| val n1 = n - 1 | ||
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| for (i in 0 until n1) { | ||
| if (i < j) { | ||
| val jr = 2 * j | ||
| val ji = jr + 1 | ||
| val ir = 2 * i | ||
| val ii = ir + 1 | ||
| val tre = riArray[jr] | ||
| val tim = riArray[ji] | ||
| riArray[jr] = riArray[ir] | ||
| riArray[ji] = riArray[ii] | ||
| riArray[ir] = tre | ||
| riArray[ii] = tim | ||
| } | ||
| k = n2 | ||
| while (k <= j) { | ||
| j -= k | ||
| k = k shr 1 | ||
| } | ||
| j += k | ||
| } | ||
| } |
73 changes: 73 additions & 0 deletions
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NoiseCapture/src/commonMain/kotlin/org/noise_planet/noisecapture/signal/ifft.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,73 @@ | ||
| package org.noise_planet.noisecapture.signal | ||
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| import kotlin.math.PI | ||
| import kotlin.math.cos | ||
| import kotlin.math.log2 | ||
| import kotlin.math.pow | ||
| import kotlin.math.sin | ||
|
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| fun iFFT(length: Int, riArray: DoubleArray) { | ||
| val m = log2(length.toDouble()).toInt() | ||
| val n = (2.0.pow(m) + 0.5).toInt() | ||
| require(n <= riArray.size) | ||
| var wCos: Double | ||
| var wSin: Double | ||
| var uCos: Double | ||
| var uSin: Double | ||
| val n2 = n shr 1 | ||
| var l1 = n | ||
| var l2: Int | ||
|
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| for (l in 0 until m) { | ||
| l2 = l1 shr 1 | ||
| wCos = 1.0 | ||
| wSin = 0.0 | ||
| uCos = cos(PI / l2) | ||
| uSin = sin(PI / l2) | ||
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| for (j in 0 until l2) { | ||
| for (i in j until n step l1) { | ||
| val ir = 2 * i | ||
| val ii = ir + 1 | ||
| val l22 = 2 * l2 | ||
| val sumRe = 0.5 * (riArray[ir] + riArray[ir + l22]) | ||
| val sumIm = 0.5 * (riArray[ii] + riArray[ii + l22]) | ||
| val diffRe = 0.5 * (riArray[ir] - riArray[ir + l22]) | ||
| val diffIm = 0.5 * (riArray[ii] - riArray[ii + l22]) | ||
| riArray[ir + l22] = diffRe * wCos - diffIm * wSin | ||
| riArray[ii + l22] = diffRe * wSin + diffIm * wCos | ||
| riArray[ir] = sumRe | ||
| riArray[ii] = sumIm | ||
| } | ||
| val w = wCos * uCos - wSin * uSin | ||
| wSin = wCos * uSin + wSin * uCos | ||
| wCos = w | ||
| } | ||
| l1 = l1 shr 1 | ||
| } | ||
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| var k: Int | ||
| var j = 0 | ||
| val n1 = n - 1 | ||
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| for (i in 0 until n1) { | ||
| if (i < j) { | ||
| val jr = 2 * j | ||
| val ji = jr + 1 | ||
| val ir = 2 * i | ||
| val ii = ir + 1 | ||
| val tre = riArray[jr] | ||
| val tim = riArray[ji] | ||
| riArray[jr] = riArray[ir] | ||
| riArray[ji] = riArray[ii] | ||
| riArray[ir] = tre | ||
| riArray[ii] = tim | ||
| } | ||
| k = n2 | ||
| while (k <= j) { | ||
| j -= k | ||
| k = k shr 1 | ||
| } | ||
| j += k | ||
| } | ||
| } |
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NoiseCapture/src/commonMain/kotlin/org/noise_planet/noisecapture/signal/realfft.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,40 @@ | ||
| package org.noise_planet.noisecapture.signal | ||
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| import kotlin.math.PI | ||
| import kotlin.math.cos | ||
| import kotlin.math.log2 | ||
| import kotlin.math.pow | ||
| import kotlin.math.sin | ||
|
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| fun realFFT(length: Int, realArray: DoubleArray) { | ||
| val m = log2(length.toDouble()).toInt() | ||
| val n = (2.0.pow(m) + 0.5).toInt() | ||
| require(n <= realArray.size) | ||
| fft(n/2, realArray) | ||
| val a = DoubleArray(n) | ||
| val b = DoubleArray(n) | ||
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| for (i in 0 until n / 2) { | ||
| a[2 * i] = 0.5 * (1 - sin(2 * PI / n * i)) | ||
| a[2 * i + 1] = -0.5 * cos(2 * PI / n * i) | ||
| b[2 * i] = 0.5 * (1 + sin(2 * PI / n * i)) | ||
| b[2 * i + 1] = 0.5 * cos(2 * PI / n * i) | ||
| } | ||
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| for (k in 1 until n / 4 + 1) { | ||
| val k2 = 2 * k | ||
| val xr = | ||
| realArray[k2] * a[k2] - realArray[k2 + 1] * a[k2 + 1] + realArray[n - k2] * b[k2] + realArray[n - k2 + 1] * b[k2 + 1] | ||
| val xi = | ||
| realArray[k2] * a[k2 + 1] + realArray[k2 + 1] * a[k2] + realArray[n - k2] * b[k2 + 1] - realArray[n - k2 + 1] * b[k2] | ||
| val xrN = | ||
| realArray[n - k2] * a[n - k2] - realArray[n - k2 + 1] * a[n - k2 + 1] + realArray[k2] * b[n - k2] + realArray[k2 + 1] * b[n - k2 + 1] | ||
| val xiN = | ||
| realArray[n - k2] * a[n - k2 + 1] + realArray[n - k2 + 1] * a[n - k2] + realArray[k2] * b[n - k2 + 1] - realArray[k2 + 1] * b[n - k2] | ||
| realArray[k2] = xr | ||
| realArray[k2 + 1] = xi | ||
| realArray[n - k2] = xrN | ||
| realArray[n - k2 + 1] = xiN | ||
| } | ||
| } | ||
|
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