From 8231379a5148989f26b8c5fb8e8f43610557af4b Mon Sep 17 00:00:00 2001
From: ausocean-david <davidsutton@ausocean.org>
Date: Thu, 15 Dec 2022 00:42:44 +1030
Subject: [PATCH] Audiofiltering:

Increase the efficieny and stability of algorithms by making use of waitgroups and goroutines.
---
 cmd/audiofiltering/main.go | 185 ++++++++++++++-----------------------
 1 file changed, 70 insertions(+), 115 deletions(-)

diff --git a/cmd/audiofiltering/main.go b/cmd/audiofiltering/main.go
index 5fec888e..8a66ed22 100644
--- a/cmd/audiofiltering/main.go
+++ b/cmd/audiofiltering/main.go
@@ -6,9 +6,9 @@ import(
 	"os"
 	"encoding/binary"
 	"github.com/mjibson/go-dsp/fft"
-	// "github.com/mjibson/go-dsp/window"
 	"math/cmplx"
 	"time"
+	"sync"
 )
 
 // define constants used in the generation of the sound waves
@@ -21,18 +21,27 @@ const(
 
 func main() {
 
+	var wg1, wg2 sync.WaitGroup
 	start := time.Now()
 	
-	// generate two sine waves with different frequencies to test frequency response
-	n := 2
+	// generate sine waves with different frequencies to test frequency response
+	n := 100
+	wg1.Add(n)
 	audio := make([][]float64, n)
-	// for i:=0; i<n; i++ {
-	// 	audio[i] = generate(float64((i)*(22000/n)))
-	// }
-	audio[0] = generate(2000)
-	audio[1] = generate(10000)
-
+	for i:=0; i<n; i++ {
+		go func(i int, audio [][]float64, wg *sync.WaitGroup) {
+			audio[i] = generate(float64((i)*(22000/n)))
+			wg.Done()
+		} (i, audio, &wg1)
+	}
+	
+	// create filter
+	filterLen := 500
+	wg2.Add(1)
+	ch := make(chan []float64, 1)
+	go LowPass(filterLen, 5000, &wg2, ch)
 
+	wg1.Wait()
 	// combine audio
 	combinedAudio := make([]float64, length)
 	for i := range audio[0] {
@@ -41,25 +50,19 @@ func main() {
 			combinedAudio[i] += audio[j][i]
 		}
 	}
-	fmt.Println("audio generation:", time.Since(start))
-	start = time.Now()
 
-	filterLen := 500
-	filter := LowPass(filterLen, 20000)
-	fmt.Println("audio filter generation:", time.Since(start))
-	start = time.Now()
+	wg2.Wait()
+	filter := <- ch
 
 	// convolve sinc with audio
-	filteredAudio := Convolve(combinedAudio, filter)
-	fmt.Println("convolution:", time.Since(start))
-	start = time.Now()
-	SaveAudioData(filteredAudio, "lowpass")
-	SaveAudioData(combinedAudio, "unfiltered")
-	fmt.Println("audio saving:", time.Since(start))
-	start = time.Now()
-
-	// SaveAudioData(filter, "test")
-
+	wg1.Add(2)
+	go SaveAudioData(combinedAudio, "unfiltered", &wg1)
+	wg2.Add(1)
+	filteredAudio := Convolve(combinedAudio, filter, &wg2)
+	wg2.Wait()
+	go SaveAudioData(filteredAudio, "lowpass", &wg1)
+	
+	wg1.Wait()
 	fmt.Println(time.Since(start))
 
 }
@@ -77,105 +80,48 @@ func generate(Frequency float64) []float64 {
 
 	// generate samples and write to file
 	for i := 0; i < int(nsamps); i++ {
-		samp[i] = math.Sin(angle * Frequency * float64(i))
+		samp[i] = math.Sin(angle * Frequency * float64(4*i))
 	}
 
 	return samp
 
 }
 
-func TopFive (a []float64) (topVal []float64, topI []int) {
-
-	length := 5
-	runMax := make([]float64, length, length)
-	indices := make([]int, length, length)
-	
-	for i:=range a {
-		switch {
-			case a[i] > runMax[0]:
-				for i:=0; i<4; i++ {
-					runMax[4-i] = runMax[4-(1+i)]
-					indices[4-i] = indices[4-(1+i)]
-				}
-				runMax[0] = a[i]
-				indices[0] = i
-			case a[i] > runMax[1]:
-				for i:=0; i<3; i++ {
-					runMax[4-i] = runMax[4-(1+i)]
-					indices[4-i] = indices[4-(1+i)]
-				}
-				runMax[1] = a[i]
-				indices[1] = i
-			case a[i] > runMax[2]:
-				for i:=0; i<2; i++ {
-					runMax[4-i] = runMax[4-(1+i)]
-					indices[4-i] = indices[4-(1+i)]
-				}
-				runMax[2] = a[i]
-				indices[2] = i
-			case a[i] > runMax[3]:
-				for i:=0; i<1; i++ {
-					runMax[4-i] = runMax[4-(1+i)]
-					indices[4-i] = indices[4-(1+i)]
-				}
-				runMax[3] = a[i]
-				indices[3] = i
-		}
-	}
-
-	return runMax, indices
-
-}
-
-func Max (a []float64) float64 {
-
-	var runMax float64 = -1
-	for i:= range a {
-		if math.Abs(a[i]) > runMax {
-			runMax = math.Abs(a[i])
-		}
-	}
-
-	return runMax
-
-}
-
-func LowPass (n int, fc float64) (filter []float64) {
+func LowPass (n int, fc float64, wg *sync.WaitGroup, ch chan []float64) {
 
 	// n is number of points on either side of 0
 	// determine digital frequency equivalent for fc
-	fd := fc/(2*SampleRate)
+	fd := (fc*4)/(2*SampleRate)
 	// create sinc function
-	return Sinc(n, fd)
-
+	ch <- Sinc(n, fd)
+	wg.Done()	
 
 }
 
-func Convolve (x, h []float64) []float64 {
+func Convolve (x, h []float64, wg *sync.WaitGroup) []float64 {
 
 	convLen := len(x)+len(h)
 	y := make([]float64, convLen)
 	for n:=0; n<convLen; n++ {
-		go SubConvolve(n, x, h, y)
+		wg.Add(1)
+		go func (n int, x, h, y []float64, wg *sync.WaitGroup) {
+			var sum float64 = 0
+			for k:=0; k<len(x); k++ {
+				if n-k >= 0 && n-k < len(h) {
+					sum += x[k]*h[n-k]
+				}
+			}
+			y[n] = sum
+			wg.Done()
+		}(n, x, h, y, wg)
 	}
-
+	wg.Done()
 	return y
 
 }
 
-func SubConvolve (n int, x, h, y []float64) {
-	var sum float64 = 0
-	for k:=0; k<len(x); k++ {
-		if n-k >= 0 && n-k < len(h) {
-			sum += x[k]*h[n-k]
-		}
-	}
-	y[n] = sum
-}
+func SaveAudioData (signal []float64, fileName string, wg1 *sync.WaitGroup) {
 
-
-func SaveAudioData (signal []float64, fileName string) {
-	
 	// compute fft of signal
 	FFTaudio := fft.FFTReal(signal)
 
@@ -188,23 +134,32 @@ func SaveAudioData (signal []float64, fileName string) {
 	for i := range spectrum {
 		spectrum[i] = spectrum[i]/maximum
 	}
-	// spectrumAlt := spectrum[0:length/2 + 1]
 
 	// SAVE
-	file := fileName + ".txt"
-	f, _ := os.Create(file)
-	for i:=0; i<20000; i++ {
-		fmt.Fprintf(f, "%v\n", /*10*math.Log10*/(spectrum[i]))
-	}
-	fmt.Printf("Saved spectrum values to: %s\n", fileName)
+	wg1.Add(2)
+	go func (fileName string, length int, spectrum []float64, wg1 *sync.WaitGroup) {
+		file := fileName + ".txt"
+		f, _ := os.Create(file)
+		for i:=0; i<20000; i++ {
+			fmt.Fprintf(f, "%v\n", /*10*math.Log10*/(spectrum[i]))
+		}
+		fmt.Printf("Saved spectrum values to: %s\n", fileName)
+		wg1.Done()
+	}(fileName, 44100, spectrum, wg1)
+	
+	go func (fileName string, signal []float64, wg1 *sync.WaitGroup) {
+		file := fileName + ".bin"
+		f, _ := os.Create(file)
+		var buf [8]byte
+		for i:=0; i<length; i++ {
+			binary.LittleEndian.PutUint32(buf[:], math.Float32bits(float32(signal[i])))
+			_, _ = f.Write(buf[:])
+		}
+		fmt.Printf("Saved binary values to: %s\n", fileName)
+		wg1.Done()
+	}(fileName, signal, wg1)
 
-	file = fileName + ".bin"
-	f, _ = os.Create(file)
-	var buf [8]byte
-	for i:=0; i<length; i++ {
-		binary.LittleEndian.PutUint32(buf[:], math.Float32bits(float32(signal[i])))
-		_, _ = f.Write(buf[:])
-	}
+	wg1.Done()
 
 }