mirror of https://bitbucket.org/ausocean/av.git
Audiofiltering:
Improve filter performance by reducing frequency leakage.
This commit is contained in:
ausocean-david
parent
fcc7d72b0b
commit
49db1041d3
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@ -6,6 +6,7 @@ import(
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"os"
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"encoding/binary"
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"github.com/mjibson/go-dsp/fft"
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"github.com/mjibson/go-dsp/window"
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"math/cmplx"
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"time"
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"sync"
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@ -36,7 +37,7 @@ func main() {
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}
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// create filter
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filterLen := 25
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filterLen := 500
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wg2.Add(1)
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ch := make(chan []float64, 1)
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go HighPass(filterLen, 2000, &wg2, ch)
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@ -55,12 +56,12 @@ func main() {
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filter := <- ch
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// convolve sinc with audio
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wg1.Add(2)
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go SaveAudioData(combinedAudio, "unfiltered", &wg1)
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wg1.Add(1)
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// go SaveAudioData(combinedAudio, "unfiltered", &wg1)
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wg2.Add(1)
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filteredAudio := Convolve(combinedAudio, filter, &wg2)
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wg2.Wait()
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go SaveAudioData(filteredAudio, "highpass", &wg1)
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go SaveAudioData(filteredAudio, "highpass-2KHz", &wg1)
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wg1.Wait()
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fmt.Println(time.Since(start))
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@ -100,29 +101,41 @@ func Max (a []float64) float64 {
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}
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func LowPass (n int, fc float64, wg *sync.WaitGroup, ch chan []float64) {
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func LowPass (taps int, fc float64, wg *sync.WaitGroup, ch chan []float64) {
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// n is number of points on either side of 0
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// determine digital frequency equivalent for fc
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fd := (fc*4)/(2*SampleRate)
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// create sinc function
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ch <- Sinc(n, fd)
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size := taps + 1
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fd := fc/SampleRate
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b := (2*math.Pi) * fd
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filter := make([]float64, size)
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winData := window.FlatTop(size)
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for n:=0; n<(taps/2); n++ {
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c := float64(n) - float64(taps)/2
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y := math.Sin(c*b) / (math.Pi * c)
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filter[n] = y * winData[n]
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filter[size-1-n] = filter[n]
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}
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filter[taps/2] = 2*fd*winData[taps/2]
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ch <- filter
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wg.Done()
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}
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func HighPass (n int, fc float64, wg *sync.WaitGroup, ch chan []float64) {
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func HighPass (taps int, fc float64, wg *sync.WaitGroup, ch chan []float64) {
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// n is number of points on either side of 0
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// determine digital frequency equivalent for fc
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fd := 0.5-((2*fc)/(SampleRate))
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fmt.Println(fd)
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// create sinc function
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filter := Sinc(n, fd)
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// convert lowpass to highpass filter
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for i:=-n; i<=n; i++ {
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filter[i+n] = filter[i+n] * math.Pow(-1, float64(i))
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size := taps + 1
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fd := fc/SampleRate
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b := (2*math.Pi) * fd
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filter := make([]float64, size)
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winData := window.FlatTop(size)
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for n:=0; n<(taps/2); n++ {
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c := float64(n) - float64(taps)/2
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y := math.Sin(c*b) / (math.Pi * c)
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filter[n] = -y * winData[n]
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filter[size-1-n] = filter[n]
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}
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filter[taps/2] = (1 - 2*fd) * winData[taps/2]
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ch <- filter
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wg.Done()
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@ -130,11 +143,12 @@ func HighPass (n int, fc float64, wg *sync.WaitGroup, ch chan []float64) {
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func Convolve (x, h []float64, wg *sync.WaitGroup) []float64 {
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convLen := len(x)+len(h)
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// conv waitgroup
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// var convwg sync.WaitGroup
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convLen := len(x)+len(h)-1
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y := make([]float64, convLen)
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for n:=0; n<convLen; n++ {
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wg.Add(1)
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go func (n int, x, h, y []float64, wg *sync.WaitGroup) {
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go func(n int, y []float64) {
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var sum float64 = 0
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for k:=0; k<len(x); k++ {
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if n-k >= 0 && n-k < len(h) {
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@ -142,8 +156,8 @@ func Convolve (x, h []float64, wg *sync.WaitGroup) []float64 {
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}
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}
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y[n] = sum
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wg.Done()
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}(n, x, h, y, wg)
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} (n, y)
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}
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wg.Done()
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return y
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@ -160,6 +174,10 @@ func SaveAudioData (signal []float64, fileName string, wg1 *sync.WaitGroup) {
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for i := range FFTaudio {
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spectrum[i] = cmplx.Abs(FFTaudio[i])/float64(length)
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}
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// maximum := Max(signal)
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// for i := range signal {
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// signal[i] = signal[i]/maximum
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// }
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maximum := Max(spectrum)
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for i := range spectrum {
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spectrum[i] = spectrum[i]/maximum
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@ -170,8 +188,8 @@ func SaveAudioData (signal []float64, fileName string, wg1 *sync.WaitGroup) {
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go func (fileName string, length int, spectrum []float64, wg1 *sync.WaitGroup) {
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file := fileName + ".txt"
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f, _ := os.Create(file)
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for i:=0; i<20000; i++ {
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fmt.Fprintf(f, "%v\n", /*20*math.Log10*/(spectrum[i]))
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for i:=0; i<len(spectrum)/2; i++ {
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fmt.Fprintf(f, "%v\n", 20*math.Log10(spectrum[i]))
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}
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fmt.Printf("Saved spectrum values to: %s\n", fileName)
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wg1.Done()
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@ -181,8 +199,8 @@ func SaveAudioData (signal []float64, fileName string, wg1 *sync.WaitGroup) {
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file := fileName + ".bin"
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f, _ := os.Create(file)
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var buf [8]byte
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for i:=0; i<length; i++ {
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binary.LittleEndian.PutUint32(buf[:], math.Float32bits(float32(signal[i])))
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for i:=0; i<len(signal); i++ {
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binary.LittleEndian.PutUint64(buf[:], math.Float64bits(signal[i]))
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_, _ = f.Write(buf[:])
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}
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fmt.Printf("Saved binary values to: %s\n", fileName)
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@ -193,18 +211,26 @@ func SaveAudioData (signal []float64, fileName string, wg1 *sync.WaitGroup) {
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}
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func Sinc (nsamps int, fc float64) []float64 {
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// func SincRedundant (nsamps int, fc float64) []float64 {
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// n is number of samples either side of n = 0
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h := make([]float64, nsamps*2 + 1)
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for n:=-nsamps; n<=nsamps; n++ {
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if n == 0 {
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h[n+nsamps] = 2*fc
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} else {
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h[n+nsamps] = math.Sin(2*math.Pi*fc*float64(n))/(math.Pi*float64(n))
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}
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}
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// // n is number of samples either side of n = 0
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// h := make([]float64, nsamps*2 + 1)
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// for n:=-nsamps; n<=nsamps; n++ {
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// if n == 0 {
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// h[n+nsamps] = 2*fc
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// } else {
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// h[n+nsamps] = math.Sin(2*math.Pi*fc*float64(n))/(math.Pi*float64(n))
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// }
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// }
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return h
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// return h
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}
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// }
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// func Sinc (x float64) float64 {
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// if x == 0 {
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// return
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// } else {
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// h[n+nsamps] = math.Sin(2*math.Pi*fc*float64(n))/(math.Pi*float64(n))
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// }
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// }
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