Audiofiltering:

Add highpass filter functionality.

cmd/audiofiltering/main.go

@@ -36,10 +36,10 @@ func main() {
 	}
 	
 	// create filter
-	filterLen := 500
+	filterLen := 25
 	wg2.Add(1)
 	ch := make(chan []float64, 1)
-	go LowPass(filterLen, 5000, &wg2, ch)
+	go HighPass(filterLen, 2000, &wg2, ch)
 
 	wg1.Wait()
 	// combine audio
@@ -60,7 +60,7 @@ func main() {
 	wg2.Add(1)
 	filteredAudio := Convolve(combinedAudio, filter, &wg2)
 	wg2.Wait()
-	go SaveAudioData(filteredAudio, "lowpass", &wg1)
+	go SaveAudioData(filteredAudio, "highpass", &wg1)
 	
 	wg1.Wait()
 	fmt.Println(time.Since(start))
@@ -87,6 +87,19 @@ func generate(Frequency float64) []float64 {
 
 }
 
+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, wg *sync.WaitGroup, ch chan []float64) {
 
 	// n is number of points on either side of 0
@@ -98,6 +111,23 @@ func LowPass (n int, fc float64, wg *sync.WaitGroup, ch chan []float64) {
 
 }
 
+func HighPass (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 := 0.5-((2*fc)/(SampleRate))
+	fmt.Println(fd)
+	// create sinc function
+	filter := Sinc(n, fd)
+	// convert lowpass to highpass filter
+	for i:=-n; i<=n; i++ {
+		filter[i+n] = filter[i+n] * math.Pow(-1, float64(i))
+	}
+	ch <- filter
+	wg.Done()	
+
+}
+
 func Convolve (x, h []float64, wg *sync.WaitGroup) []float64 {
 
 	convLen := len(x)+len(h)
@@ -141,7 +171,7 @@ func SaveAudioData (signal []float64, fileName string, 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.Fprintf(f, "%v\n", /*20*math.Log10*/(spectrum[i]))
 		}
 		fmt.Printf("Saved spectrum values to: %s\n", fileName)
 		wg1.Done()