Audiofiltering:

Add amplifying capabilities, using Filter.Upper as the factor for amplification
This commit is contained in:
ausocean-david 2022-12-28 20:37:39 +10:30 committed by David Sutton
parent 52a56f3a52
commit 70afcdb816
6 changed files with 671 additions and 320 deletions

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@ -1,94 +0,0 @@
package main
import (
"fmt"
"math"
"os"
"time"
"bitbucket.org/ausocean/av/codec/pcm"
)
// main is a driver function for testing the filters defined in codec/pcm/filters.go
func main() {
// Define start time for execution timing.
start := time.Now()
// Read the audio data from the file.
input, _ := os.ReadFile("whitenoise.pcm")
// Create Buffer in struct format defined in pcm.go
format := pcm.BufferFormat{Rate: 44100, Channels: 1, SFormat: pcm.S16_LE}
buf := pcm.Buffer{Format: format, Data: input}
// Create a filter.
bs := pcm.Filter{BuffInfo: buf.Format, Type: pcm.BANDSTOP, Lower: 1000, Upper: 2000, Taps: 500}
// Apply different filters to save and compare.
bs.Generate()
bs_1khz := bs.Apply(buf)
fmt.Println("Applied 1Khz Bandstop filter")
bs.Lower, bs.Upper = 2000, 5000
bs.Generate()
bs_2khz := bs.Apply(buf)
fmt.Println("Applied 2Khz Bandstop filter")
bs.Lower, bs.Upper = 5000, 10000
bs.Generate()
bs_5khz := bs.Apply(buf)
fmt.Println("Applied 5Khz Bandstop filter")
bs.Lower, bs.Upper = 10000, 15000
bs.Generate()
bs_10khz := bs.Apply(buf)
fmt.Println("Applied 10Khz Bandstop filter")
bs.Lower, bs.Upper = 15000, 18000
bs.Generate()
bs_15khz := bs.Apply(buf)
fmt.Println("Applied 15Khz Bandstop filter")
// Save the transformed audio.
f, _ := os.Create("bs_1khz.pcm")
f.Write(bs_1khz)
fmt.Println("Wrote audio to bs_1khz.pcm")
f, _ = os.Create("bs_2khz.pcm")
f.Write(bs_2khz)
fmt.Println("Wrote audio to bs_2khz.pcm")
f, _ = os.Create("bs_5khz.pcm")
f.Write(bs_5khz)
fmt.Println("Wrote audio to bs_5khz.pcm")
f, _ = os.Create("bs_10khz.pcm")
f.Write(bs_10khz)
fmt.Println("Wrote audio to bs_10khz.pcm")
f, _ = os.Create("bs_15khz.pcm")
f.Write(bs_15khz)
fmt.Println("Wrote audio to bs_15khz.pcm")
// Display execution time.
fmt.Println("Finished execution. Total time:", time.Since(start))
}
// LEGACY FUNCTION FOR TESTING
// generate is used to generate a sine wave of the given frequency, calls on the global variables of Duration and SampleRate (bytes)
func generate(freq float64, SampleRate, duration int) []byte {
// Create slices to store values.
signal := make([]byte, 2*duration*SampleRate)
t := make([]float64, 2*duration*SampleRate)
// Generate the values to plot.
for n := range t {
t[n] = math.Pi * float64(n) / float64(SampleRate)
signal[n] = byte(math.Round(127 * math.Sin(freq*t[n])))
}
return signal
}

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@ -1,274 +1,328 @@
/*
NAME
filters.go
DESCRIPTION
filter.go contains functions for filtering PCM audio.
AUTHOR
David Sutton <davidsutton@ausocean.org>
LICENSE
filters_test.go is Copyright (C) 2023 the Australian Ocean Lab (AusOcean)
It is free software: you can redistribute it and/or modify them
under the terms of the GNU General Public License as published by the
Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
It is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License in gpl.txt.
If not, see [GNU licenses](http://www.gnu.org/licenses).
*/
package pcm
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"math"
"sync"
"github.com/mjibson/go-dsp/fft"
"github.com/mjibson/go-dsp/window"
)
// FilterType is the type of filter which can be generated.
type FilterType int
// Currently implemented filter types.
const (
LOWPASS FilterType = iota
HIGHPASS
BANDPASS
BANDSTOP
AMPLIFIER
)
// Filter contains the specifications of the filter, as well as the coefficients to the filter function itself.
type Filter struct {
Coeffs []float64
Type FilterType
SampleRate uint
Lower, Upper float64
Taps int
BuffInfo BufferFormat
}
// AudioFilter interface contains Generate and Apply. Generate is used to generate the coefficients of the filter based off
// the specifications within the Filter struct.
// AudioFilter is an interface which contains an Apply function.
// Apply is used to apply the filter to the given buffer of PCM data (b.Data).
type AudioFilter interface {
Generate()
Apply(b Buffer)
}
// Generate is used to generate the coefficients of the filter function used for convolution with a signal to
// perform specified filter.
func (filter *Filter) Generate() {
// Update the sample rate from the buffer info (if supplied).
if filter.BuffInfo.Rate != 0 {
filter.SampleRate = filter.BuffInfo.Rate
}
// Determine the type of filter to generate (based off filter.Type).
switch filter.Type {
case LOWPASS:
// Create a lowpass filter with characteristics from struct.
size := filter.Taps + 1
filter.Coeffs = make([]float64, size, size)
fd := (filter.Upper) / float64(filter.SampleRate)
b := (2 * math.Pi) * fd
winData := window.FlatTop(size)
for n := 0; n < (filter.Taps / 2); n++ {
c := float64(n) - float64(filter.Taps)/2
y := math.Sin(c*b) / (math.Pi * c)
filter.Coeffs[n] = (y * winData[n])
filter.Coeffs[size-1-n] = filter.Coeffs[n]
}
filter.Coeffs[filter.Taps/2] = 2 * fd * winData[filter.Taps/2]
case HIGHPASS:
// Create a HighIGHPASSass filter with characteristics from struct.
size := filter.Taps + 1
filter.Coeffs = make([]float64, size, size)
fd := (filter.Lower) / float64(filter.SampleRate)
b := (2 * math.Pi) * fd
winData := window.FlatTop(size)
for n := 0; n < (filter.Taps / 2); n++ {
c := float64(n) - float64(filter.Taps)/2
y := math.Sin(c*b) / (math.Pi * c)
filter.Coeffs[n] = -y * winData[n]
filter.Coeffs[size-1-n] = filter.Coeffs[n]
}
filter.Coeffs[filter.Taps/2] = (1 - 2*fd) * winData[filter.Taps/2]
case BANDPASS:
// Make Low and HighIGHPASSass filters.
lowpass := Filter{Type: LOWPASS, SampleRate: filter.SampleRate, Upper: filter.Upper, Taps: filter.Taps}
highpass := Filter{Type: HIGHPASS, SampleRate: filter.SampleRate, Lower: filter.Lower, Taps: filter.Taps}
lowpass.Generate()
highpass.Generate()
// Convolve lowpass filter with highIGHPASSass filter to get bandpass filter.
var wg sync.WaitGroup
ch := make(chan []float64, 1)
wg.Add(1)
go FastConvolve(lowpass.Coeffs, highpass.Coeffs, &wg, ch)
wg.Wait()
filter.Coeffs = <-ch
case BANDSTOP:
// Make Low and Highpass filters.
lowpass := Filter{Type: LOWPASS, SampleRate: filter.SampleRate, Upper: filter.Lower, Taps: filter.Taps}
highpass := Filter{Type: HIGHPASS, SampleRate: filter.SampleRate, Lower: filter.Upper, Taps: filter.Taps}
lowpass.Generate()
highpass.Generate()
// Add lowpass filter to highpass filter to get bandstop filter.
size := filter.Taps + 1
filter.Coeffs = make([]float64, size, size)
for i := range lowpass.Coeffs {
filter.Coeffs[i] = lowpass.Coeffs[i] + highpass.Coeffs[i]
}
}
// SelectiveFrequencyFilter is a struct which contains all the filter specifications required for a
// lowpass, highpass, bandpass, or bandstop filter.
type SelectiveFrequencyFilter struct {
coeffs []float64
cutoff [2]float64
sampleRate uint
taps int
buffInfo BufferFormat
}
// Apply takes in a buffer of PCM audio, applies the filter and returns the filtered audio (in byte slice)
func (filter *Filter) Apply(b Buffer) []byte {
// NewLowPass populates a LowPass struct with the specified data. The function also
// generates a lowpass filter based off the given specifications, and returns a pointer.
func NewLowPass(fc float64, info BufferFormat, length int) (*SelectiveFrequencyFilter, error) {
return newLoHiFilter(fc, info, length, [2]float64{0, fc})
}
// Convert input to floats.
inputAsFloat := make([]float64, len(b.Data)/2)
temp := make([]byte, 2)
// NewHighPass populates a HighPass struct with the specified data. The function also
// generates a highpass filter based off the given specifications, and returns a pointer.
func NewHighPass(fc float64, info BufferFormat, length int) (*SelectiveFrequencyFilter, error) {
return newLoHiFilter(fc, info, length, [2]float64{fc, 0})
}
// NewBandPass populates a BandPass struct with the specified data. The function also
// generates a bandpass filter based off the given specifications, and returns a pointer.
func NewBandPass(fc_lower, fc_upper float64, info BufferFormat, length int) (*SelectiveFrequencyFilter, error) {
newFilter, lp, hp, err := newBandFilter([2]float64{fc_lower, fc_upper}, info, length)
if err != nil {
return nil, fmt.Errorf("could not create new band filter: %w", err)
}
// Convolve the filters to create a bandpass filter.
newFilter.coeffs, err = fastConvolve(hp.coeffs, lp.coeffs)
if err != nil {
return nil, fmt.Errorf("could not compute fast convolution: %w", err)
}
// Return a pointer to the filter.
return newFilter, nil
}
// NewBandStop populates a BandStop struct with the specified data. The function also
// generates a bandstop filter based off the given specifications, and returns a pointer.
func NewBandStop(fc_lower, fc_upper float64, info BufferFormat, length int) (*SelectiveFrequencyFilter, error) {
newFilter, lp, hp, err := newBandFilter([2]float64{fc_upper, fc_lower}, info, length)
if err != nil {
return nil, fmt.Errorf("could not create new band filter: %w", err)
}
size := newFilter.taps + 1
newFilter.coeffs = make([]float64, size)
for i := range lp.coeffs {
newFilter.coeffs[i] = lp.coeffs[i] + hp.coeffs[i]
}
// Return a pointer to the filter.
return newFilter, nil
}
// Apply is the SelectiveFrequencyFilter implementation of the AudioFilter interface. This implementation
// takes the buffer data (b.Data), applies the highpass filter and returns a byte slice of filtered audio.
func (filter *SelectiveFrequencyFilter) Apply(b Buffer) ([]byte, error) {
// Apply the lowpass filter to the given audio buffer.
return convolveFromBytes(b.Data, filter.coeffs)
}
// Amplifier is a struct which contains the factor of amplification to be used in the application
// of the filter.
type Amplifier struct {
factor float64
}
// NewAmplifier defines the factor of amplification for an amplifying filter.
func NewAmplifier(factor float64) Amplifier {
// Return populated Amplifier filter.
// Uses the absolute value of the factor to ensure compatibility.
return Amplifier{factor: math.Abs(factor)}
}
// Apply implemented for an amplifier takes the buffer data (b.Data), applies
// the amplification and returns a byte slice of filtered audio.
func (amp *Amplifier) Apply(b Buffer) ([]byte, error) {
inputAsFloat, err := bytesToFloats(b.Data)
if err != nil {
return nil, fmt.Errorf("failed to convert to floats: %w", err)
}
// Multiply every sample by the factor of amplification.
floatOutput := make([]float64, len(inputAsFloat))
for i := range inputAsFloat {
temp[0] = b.Data[2*i]
temp[1] = b.Data[2*i+1]
inputAsFloat[i] = float64(binary.LittleEndian.Uint16(temp))
if inputAsFloat[i] > 32767 {
inputAsFloat[i] -= 32768 * 2
floatOutput[i] = inputAsFloat[i] * amp.factor
// Stop audio artifacting by clipping outputs.
if floatOutput[i] > 1 {
floatOutput[i] = 1
} else if floatOutput[i] < -1 {
floatOutput[i] = -1
}
inputAsFloat[i] /= (32767)
}
outBytes, err := floatsToBytes(floatOutput)
if err != nil {
return nil, fmt.Errorf("failed to convert to bytes: %w", err)
}
return outBytes, nil
}
// newLoHiFilter is a function which checks for the validity of the input parameters, and calls the newLoHiFilter function
// to return a pointer to either a lowpass or a highpass filter.
func newLoHiFilter(fc float64, info BufferFormat, length int, cutoff [2]float64) (*SelectiveFrequencyFilter, error) {
// Ensure that all input values are valid.
if fc <= 0 || fc >= float64(info.Rate)/2 {
return nil, errors.New("cutoff frequency out of bounds")
} else if length <= 0 {
return nil, errors.New("cannot create filter with length <= 0")
}
var convolution []float64
// Check if filter type is frequency filter or amplifier.
if filter.Type == AMPLIFIER {
convolution = make([]float64, len(inputAsFloat))
for i := range inputAsFloat {
convolution[i] = inputAsFloat[i] * filter.Upper
// Stop audio artifacting by clipping outputs
if convolution[i] > 1 {
convolution[i] = 1
} else if convolution[i] < -1 {
convolution[i] = -1
}
}
// Determine the type of filter to be generated.
var fd float64
var factor1 float64
var factor2 float64
if cutoff[0] == 0 { // For a lowpass filter, cutoff[0] = 0, cutoff[1] = fc.
// The filter must be a lowpass filter.
fd = cutoff[1] / float64(info.Rate)
factor1 = 1
factor2 = 2 * fd
} else if cutoff[1] == 0 { // For a highpass filter, cutoff[0] = fc, cutoff[1] = 0.
// The filter must be a highpass filter.
fd = cutoff[0] / float64(info.Rate)
factor1 = -1
factor2 = 1 - 2*fd
} else {
// Convolve input with filter.
var wg sync.WaitGroup
ch := make(chan []float64, 1)
wg.Add(1)
go FastConvolve(inputAsFloat, filter.Coeffs, &wg, ch)
wg.Wait()
convolution = <-ch
// Otherwise the filter must be a different type of filter.
return nil, errors.New("tried to use newLoHiFilter to generate bandpass or bandstop filter")
}
// Convert convolution output back to bytes.
var output []byte
buf := make([]byte, 2)
for i := range convolution {
if convolution[i] >= 1 {
convolution[i] = 0.9999
} else if convolution[i] <= -1 {
convolution[i] = -0.9999
}
convolution[i] = convolution[i] * 32767
if convolution[i] < 0 {
convolution[i] = convolution[i] + 32767*2
}
binary.LittleEndian.PutUint16(buf[:], uint16(convolution[i]))
output = append(output, buf[0], buf[1])
// Create a new filter struct to return, populated with all correct data.
var newFilter = SelectiveFrequencyFilter{cutoff: cutoff, sampleRate: info.Rate, taps: length, buffInfo: info}
// Create a filter with characteristics from struct.
size := newFilter.taps + 1
newFilter.coeffs = make([]float64, size)
b := 2 * math.Pi * fd
winData := window.FlatTop(size)
for n := 0; n < (newFilter.taps / 2); n++ {
c := float64(n) - float64(newFilter.taps)/2
y := math.Sin(c*b) / (math.Pi * c)
newFilter.coeffs[n] = factor1 * y * winData[n]
newFilter.coeffs[size-1-n] = newFilter.coeffs[n]
}
newFilter.coeffs[newFilter.taps/2] = factor2 * winData[newFilter.taps/2]
return output
// Return a pointer to the filter.
return &newFilter, nil
}
// Convolve takes in a signal and an FIR filter and computes the convolution. (runs in O(n^2) time)
func Convolve(x, h []float64, wg *sync.WaitGroup, ch chan []float64) {
// Create a waitgroup to be used in goroutines called by Convolution
var convwg sync.WaitGroup
// Compute the convolution
convLen := len(x) + len(h) - 1
y := make([]float64, convLen)
var progress int
for n := 0; n < convLen; n++ {
convwg.Add(1)
go func(n int, y []float64, convwg *sync.WaitGroup, progress *int) {
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]
} else if n-k < 0 {
break
}
}
y[n] = sum
*progress++
convwg.Done()
}(n, y, &convwg, &progress)
fmt.Println(float64(progress) * 100 / float64(convLen))
// newBandFilter creates a ensures the validity of the input parameters, and generates appropriate lowpass and highpass filters
// required for the creation of the specific band filter.
func newBandFilter(cutoff [2]float64, info BufferFormat, length int) (new, lp, hp *SelectiveFrequencyFilter, err error) {
// Ensure that all input values are valid.
if cutoff[0] <= 0 || cutoff[0] >= float64(info.Rate)/2 {
return nil, nil, nil, errors.New("cutoff frequencies out of bounds")
} else if cutoff[1] <= 0 || cutoff[1] >= float64(info.Rate)/2 {
return nil, nil, nil, errors.New("cutoff frequencies out of bounds")
} else if length <= 0 {
return nil, nil, nil, errors.New("cannot create filter with length <= 0")
}
convwg.Wait()
ch <- y
close(ch)
wg.Done()
// Create a new filter struct to return, populated with all correct data.
// For a bandpass filter, cutoff[0] = fc_l, cutoff[1] = fc_u.
// For a bandstop filter, cutoff[0] = fc_u, cutoff[1] = fc_l.
var newFilter = SelectiveFrequencyFilter{cutoff: cutoff, sampleRate: info.Rate, taps: length, buffInfo: info}
// Generate lowpass and highpass filters to create bandpass filter with.
hp, err = NewHighPass(newFilter.cutoff[0], newFilter.buffInfo, newFilter.taps)
if err != nil {
return nil, nil, nil, fmt.Errorf("could not create new highpass filter: %w", err)
}
lp, err = NewLowPass(newFilter.cutoff[1], newFilter.buffInfo, newFilter.taps)
if err != nil {
return nil, nil, nil, fmt.Errorf("could not create new lowpass filter: %w", err)
}
// Return pointer to new filter.
return &newFilter, hp, lp, nil
}
// FastConvolve takes in a signal and an FIR filter and computes the convolution. (runs in O(nlog(n)) time)
func FastConvolve(x, h []float64, wg *sync.WaitGroup, ch chan []float64) {
// convolveFromBytes takes in a byte slice and a float64 slice for a filter, converts to floats,
// convolves the two signals, and converts back to bytes and returns the convolution.
func convolveFromBytes(b []byte, filter []float64) ([]byte, error) {
bufAsFloats, err := bytesToFloats(b)
if err != nil {
return nil, fmt.Errorf("could not convert to floats: %w", err)
}
// Calculate the length of the linear convolution
// Convolve the floats with the filter.
convolution, err := fastConvolve(bufAsFloats, filter)
if err != nil {
return nil, fmt.Errorf("could not compute fast convolution: %w", err)
}
outBytes, err := floatsToBytes(convolution)
if err != nil {
return nil, fmt.Errorf("could not convert convolution to bytes: %w", err)
}
return outBytes, nil
}
func bytesToFloats(b []byte) ([]float64, error) {
// Ensure the validity of the input.
if len(b) == 0 {
return nil, errors.New("no audio to convert to floats")
} else if len(b)%2 != 0 {
return nil, errors.New("uneven number of bytes (not whole number of samples)")
}
// Convert bytes to floats.
inputAsFloat := make([]float64, len(b)/2)
inputAsInt := make([]int16, len(b)/2)
bReader := bytes.NewReader(b)
for i := range inputAsFloat {
binary.Read(bReader, binary.LittleEndian, &inputAsInt[i])
inputAsFloat[i] = float64(inputAsInt[i]) / (math.MaxInt16 + 1)
}
return inputAsFloat, nil
}
// floatsToBytes converts a slice of float64 PCM data into a slice of signed 16bit PCM data.
// The input float slice should contains values between -1 and 1. The function converts these values
// to a proportionate unsigned value between 0 and 65536. This 16bit integer is split into two bytes,
// then returned in Little Endian notation in a byte slice double the length of the input.
func floatsToBytes(f []float64) ([]byte, error) {
buf := new(bytes.Buffer)
bytes := make([]byte, len(f)*2)
for i := range f {
err := binary.Write(buf, binary.LittleEndian, int16(f[i]*math.MaxInt16))
if err != nil {
return nil, fmt.Errorf("failed to write ints as bytes: %w", err)
}
}
n, err := buf.Read(bytes)
if err != nil {
return nil, fmt.Errorf("failed to read bytes from buffer: %w", err)
} else if n != len(bytes) {
return nil, fmt.Errorf("buffer and output length mismatch read %d bytes, expected %d: %w", n, len(bytes), err)
}
return bytes, nil
}
// fastConvolve takes in a signal and an FIR filter and computes the convolution (runs in O(nlog(n)) time).
func fastConvolve(x, h []float64) ([]float64, error) {
// Ensure valid data to convolve.
if len(x) == 0 || len(h) == 0 {
return nil, errors.New("convolution requires slice of length > 0")
}
// Calculate the length of the linear convolution.
convLen := len(x) + len(h) - 1
// Pad signals to the next largest power of 2 larger than convLen
// Pad signals to the next largest power of 2 larger than convLen.
padLen := int(math.Pow(2, math.Ceil(math.Log2(float64(convLen)))))
zeros := make([]float64, padLen-len(x), padLen-len(h))
x = append(x, zeros...)
zeros = make([]float64, padLen-len(h))
h = append(h, zeros...)
// Compute DFFTs
X, H := fft.FFTReal(x), fft.FFTReal(h)
// Compute DFFTs.
x_fft, h_fft := fft.FFTReal(x), fft.FFTReal(h)
// Compute the multiplication of the two signals in the freq domain
var convWG sync.WaitGroup
Y := make([]complex128, padLen)
for i := range X {
convWG.Add(1)
go func(a, b complex128, y *complex128, convWG *sync.WaitGroup, i int) {
*y = a * b
convWG.Done()
}(X[i], H[i], &Y[i], &convWG, i)
// Compute the multiplication of the two signals in the freq domain.
y_fft := make([]complex128, padLen)
for i := range x_fft {
y_fft[i] = x_fft[i] * h_fft[i]
}
convWG.Wait()
// Compute the IDFFT.
iy := fft.IFFT(y_fft)
// Compute the IDFFT
iy := fft.IFFT(Y)
// Convert to []float64
// Convert to []float64.
y := make([]float64, padLen)
for i := range iy {
convWG.Add(1)
go func(a complex128, y *float64, convWG *sync.WaitGroup) {
*y = real(a)
convWG.Done()
}(iy[i], &y[i], &convWG)
}
convWG.Wait()
// Trim to length of linear convolution
ch <- y[0:convLen]
wg.Done()
}
// LEGACY FUNCTION FOR TESTING
// Max returns the absolute highest value in a given array.
func Max(a []float64) float64 {
var runMax float64 = -1
for i := range a {
if math.Abs(a[i]) > runMax {
runMax = math.Abs(a[i])
}
y[i] = real(iy[i])
}
return runMax
// Trim to length of linear convolution and return.
return y[0:convLen], nil
}

368
codec/pcm/filters_test.go Normal file
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@ -0,0 +1,368 @@
/*
NAME
filters_test.go
DESCRIPTION
filter_test.go contains functions for testing functions in filters.go.
AUTHOR
David Sutton <davidsutton@ausocean.org>
LICENSE
filters_test.go is Copyright (C) 2023 the Australian Ocean Lab (AusOcean)
It is free software: you can redistribute it and/or modify them
under the terms of the GNU General Public License as published by the
Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
It is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License in gpl.txt.
If not, see [GNU licenses](http://www.gnu.org/licenses).
*/
package pcm
import (
"math"
"math/cmplx"
"os"
"testing"
"github.com/mjibson/go-dsp/fft"
)
// Set constant values for testing.
const (
sampleRate = 44100
filterLength = 500
freqTest = 1000
)
// TestLowPass is used to test the lowpass constructor and application. Testing is done by ensuring frequency response as well as
// comparing against an expected audio file.
func TestLowPass(t *testing.T) {
// Generate an audio buffer to run test on.
genAudio, err := generate()
if err != nil {
t.Fatal(err)
}
var buf = Buffer{Data: genAudio, Format: BufferFormat{SFormat: S16_LE, Rate: sampleRate, Channels: 1}}
// Create a lowpass filter to test.
const fc = 4500.0
lp, err := NewLowPass(fc, buf.Format, filterLength)
if err != nil {
t.Fatal(err)
}
// Filter the audio.
filteredAudio, err := lp.Apply(buf)
if err != nil {
t.Fatal(err)
}
// Take the FFT of the signal.
filteredFloats, err := bytesToFloats(filteredAudio)
if err != nil {
t.Fatal(err)
}
filteredFFT := fft.FFTReal(filteredFloats)
// Check if the lowpass filter worked (any high values in filteredFFT above cutoff freq result in fail).
for i := int(fc); i < sampleRate/2; i++ {
mag := math.Pow(cmplx.Abs(filteredFFT[i]), 2)
if mag > freqTest {
t.Error("Lowpass filter failed to meet spec.")
break
}
}
// Read audio from the test location.
const fileName = "../../../test/test-data/av/input/lp_4500.pcm"
expectedAudio, err := os.ReadFile(fileName)
if err != nil {
t.Fatalf("File for comparison not read.\n\t%s", err)
}
// Compare the filtered audio against the expected signal.
compare(filteredAudio, expectedAudio, t)
}
// TestHighPass is used to test the highpass constructor and application. Testing is done by ensuring frequency response as well as
// comparing against an expected audio file.
func TestHighPass(t *testing.T) {
// Generate an audio buffer to run test on.
genAudio, err := generate()
if err != nil {
t.Fatal(err)
}
var buf = Buffer{Data: genAudio, Format: BufferFormat{SFormat: S16_LE, Rate: sampleRate, Channels: 1}}
// Create a highpass filter to test.
const fc = 4500.0
hp, err := NewHighPass(fc, buf.Format, filterLength)
if err != nil {
t.Fatal(err)
}
// Filter the audio.
filteredAudio, err := hp.Apply(buf)
if err != nil {
t.Fatal(err)
}
// Take the FFT of signal.
filteredFloats, err := bytesToFloats(filteredAudio)
if err != nil {
t.Fatal(err)
}
filteredFFT := fft.FFTReal(filteredFloats)
// Check if the highpass filter worked (any high values in filteredFFT below cutoff freq result in fail).
for i := 0; i < int(fc); i++ {
mag := math.Pow(cmplx.Abs(filteredFFT[i]), 2)
if mag > freqTest {
t.Error("Highpass Filter doesn't meet Spec", i)
}
}
// Read audio from the test location.
const fileName = "../../../test/test-data/av/input/hp_4500.pcm"
expectedAudio, err := os.ReadFile(fileName)
if err != nil {
t.Fatalf("File for comparison not read.\n\t%s", err)
}
// Compare against expected results.
compare(expectedAudio, filteredAudio, t)
}
// TestBandPass is used to test the bandpass constructor and application. Testing is done by ensuring frequency response as well as
// comparing against an expected audio file.
func TestBandPass(t *testing.T) {
// Generate an audio buffer to run test on.
genAudio, err := generate()
if err != nil {
t.Fatal(err)
}
var buf = Buffer{Data: genAudio, Format: BufferFormat{SFormat: S16_LE, Rate: sampleRate, Channels: 1}}
// Create a bandpass filter to test.
const (
fc_l = 4500.0
fc_u = 9500.0
)
hp, err := NewBandPass(fc_l, fc_u, buf.Format, filterLength)
if err != nil {
t.Fatal(err)
}
// Filter audio with filter.
filteredAudio, err := hp.Apply(buf)
if err != nil {
t.Fatal(err)
}
// Take FFT of signal.
filteredFloats, err := bytesToFloats(filteredAudio)
if err != nil {
t.Fatal(err)
}
filteredFFT := fft.FFTReal(filteredFloats)
// Check if the bandpass filter worked (any high values in filteredFFT above cutoff or below cutoff freq result in fail).
for i := 0; i < int(fc_l); i++ {
mag := math.Pow(cmplx.Abs(filteredFFT[i]), 2)
if mag > freqTest {
t.Error("Bandpass Filter doesn't meet Spec", i)
}
}
for i := int(fc_u); i < sampleRate/2; i++ {
mag := math.Pow(cmplx.Abs(filteredFFT[i]), 2)
if mag > freqTest {
t.Error("Bandpass Filter doesn't meet Spec", i)
}
}
// Read audio from test location.
const fileName = "../../../test/test-data/av/input/bp_4500-9500.pcm"
expectedAudio, err := os.ReadFile(fileName)
if err != nil {
t.Fatalf("File for comparison not read.\n\t%s", err)
}
// Compare against the expected audio.
compare(expectedAudio, filteredAudio, t)
}
// TestBandPass is used to test the bandpass constructor and application. Testing is done by ensuring frequency response as well as
// comparing against an expected audio file.
func TestBandStop(t *testing.T) {
// Generate an audio buffer to run test on.
genAudio, err := generate()
if err != nil {
t.Fatal(err)
}
var buf = Buffer{Data: genAudio, Format: BufferFormat{SFormat: S16_LE, Rate: sampleRate, Channels: 1}}
// Create a bandpass filter to test.
const (
fc_l = 4500.0
fc_u = 9500.0
)
bs, err := NewBandStop(fc_l, fc_u, buf.Format, filterLength)
if err != nil {
t.Fatal(err)
}
// Filter audio with filter.
filteredAudio, err := bs.Apply(buf)
if err != nil {
t.Fatal(err)
}
// Take FFT of signal.
filteredFloats, err := bytesToFloats(filteredAudio)
if err != nil {
t.Fatal(err)
}
filteredFFT := fft.FFTReal(filteredFloats)
// Check if the bandpass filter worked (any high values in filteredFFT above cutoff or below cutoff freq result in fail).
for i := int(fc_l); i < int(fc_u); i++ {
mag := math.Pow(cmplx.Abs(filteredFFT[i]), 2)
if mag > freqTest {
t.Error("BandStop Filter doesn't meet Spec", i)
}
}
// Read audio from test location.
const fileName = "../../../test/test-data/av/input/bs_4500-9500.pcm"
expectedAudio, err := os.ReadFile(fileName)
if err != nil {
t.Fatalf("File for comparison not read.\n\t%s", err)
}
// Compare against the expected audio.
compare(expectedAudio, filteredAudio, t)
}
// TestAmplifier is used to test the amplifier constructor and application. Testing is done by checking the maximum value before and
// after application, as well as comparing against an expected audio file.
func TestAmplifier(t *testing.T) {
// Load a simple sine wave with amplitude of 0.1 and load into buffer.
const audioFileName = "../../../test/test-data/av/input/sine.pcm"
lowSine, err := os.ReadFile(audioFileName)
if err != nil {
t.Errorf("File for filtering not read.\n\t%s", err)
t.FailNow()
}
var buf = Buffer{Data: lowSine, Format: BufferFormat{SFormat: S16_LE, Rate: sampleRate, Channels: 1}}
// Create an amplifier filter.
const factor = 5.0
amp := NewAmplifier(factor)
// Apply the amplifier to the audio.
filteredAudio, err := amp.Apply(buf)
if err != nil {
t.Fatal(err)
}
// Find the maximum sample before and after amplification.
dataFloats, err := bytesToFloats(buf.Data)
if err != nil {
t.Fatal(err)
}
preMax := max(dataFloats)
filteredFloats, err := bytesToFloats(filteredAudio)
if err != nil {
t.Fatal(err)
}
postMax := max(filteredFloats)
// Compare the values.
if preMax*factor > 1 && postMax > 0.99 {
} else if postMax/preMax > 1.01*factor || postMax/preMax < 0.99*factor {
t.Error("Amplifier failed to meet spec, expected:", factor, " got:", postMax/preMax)
}
// Load expected audio file.
const compFileName = "../../../test/test-data/av/input/amp_5.pcm"
expectedAudio, err := os.ReadFile(compFileName)
if err != nil {
t.Fatalf("File for comparison not read.\n\t%s", err)
}
// Compare against the expected audio file.
compare(filteredAudio, expectedAudio, t)
}
// generate returns a byte slice in the same format that would be read from a PCM file.
// The function generates a sound with a range of frequencies for testing against,
// with a length of 1 second.
func generate() ([]byte, error) {
// Create an slice to generate values across.
t := make([]float64, sampleRate)
s := make([]float64, sampleRate)
// Define spacing of generated frequencies.
const (
deltaFreq = 1000
maxFreq = 21000
amplitude = float64(deltaFreq) / float64((maxFreq - deltaFreq))
)
for n := 0; n < sampleRate; n++ {
t[n] = float64(n) / float64(sampleRate)
// Generate sinewaves of different frequencies.
s[n] = 0
for f := deltaFreq; f < maxFreq; f += deltaFreq {
s[n] += amplitude * math.Sin(float64(f)*2*math.Pi*t[n])
}
}
// Return the spectrum as bytes (PCM).
bytesOut, err := floatsToBytes(s)
if err != nil {
return nil, err
}
return bytesOut, nil
}
// compare takes in two audio files (S16_LE), compares them, and returns an error if the
// signals are more than 10% different at any individual sample.
func compare(a, b []byte, t *testing.T) {
// Convert to floats to compare.
aFloats, err := bytesToFloats(a)
if err != nil {
t.Fatal(err)
}
bFloats, err := bytesToFloats(b)
if err != nil {
t.Fatal(err)
}
// Compare against filtered audio.
for i := range aFloats {
diff := (bFloats[i] - aFloats[i])
if math.Abs(diff) > 0.1 {
t.Error("Filtered audio is too different to database")
return
}
}
}
// max takes a float slice and returns the absolute largest value in the slice.
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
}

View File

@ -73,9 +73,9 @@ func DataSize(rate, channels, bitDepth uint, period float64) int {
// Resample takes Buffer c and resamples the pcm audio data to 'rate' Hz and returns a Buffer with the resampled data.
// Notes:
// - Currently only downsampling is implemented and c's rate must be divisible by 'rate' or an error will occur.
// - If the number of bytes in c.Data is not divisible by the decimation factor (ratioFrom), the remaining bytes will
// not be included in the result. Eg. input of length 480002 downsampling 6:1 will result in output length 80000.
// - Currently only downsampling is implemented and c's rate must be divisible by 'rate' or an error will occur.
// - If the number of bytes in c.Data is not divisible by the decimation factor (ratioFrom), the remaining bytes will
// not be included in the result. Eg. input of length 480002 downsampling 6:1 will result in output length 80000.
func Resample(c Buffer, rate uint) (Buffer, error) {
if c.Format.Rate == rate {
return c, nil

1
go.mod
View File

@ -16,6 +16,7 @@ require (
github.com/pkg/errors v0.9.1
github.com/yobert/alsa v0.0.0-20180630182551-d38d89fa843e
gocv.io/x/gocv v0.29.0
golang.org/x/tools v0.5.0 // indirect
gonum.org/v1/gonum v0.8.2
gonum.org/v1/plot v0.9.0
gopkg.in/natefinch/lumberjack.v2 v2.0.0

22
go.sum
View File

@ -96,6 +96,7 @@ github.com/tarm/serial v0.0.0-20180830185346-98f6abe2eb07/go.mod h1:kDXzergiv9cb
github.com/yobert/alsa v0.0.0-20180630182551-d38d89fa843e h1:3NIzz7weXhh3NToPgbtlQtKiVgerEaG4/nY2skGoGG0=
github.com/yobert/alsa v0.0.0-20180630182551-d38d89fa843e/go.mod h1:CaowXBWOiSGWEpBBV8LoVnQTVPV4ycyviC9IBLj8dRw=
github.com/yryz/ds18b20 v0.0.0-20180211073435-3cf383a40624/go.mod h1:MqFju5qeLDFh+S9PqxYT7TEla8xeW7bgGr/69q3oki0=
github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
go.uber.org/atomic v1.3.2 h1:2Oa65PReHzfn29GpvgsYwloV9AVFHPDk8tYxt2c2tr4=
go.uber.org/atomic v1.3.2/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
go.uber.org/multierr v1.1.0 h1:HoEmRHQPVSqub6w2z2d2EOVs2fjyFRGyofhKuyDq0QI=
@ -109,6 +110,7 @@ golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACk
golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
golang.org/x/exp v0.0.0-20180321215751-8460e604b9de/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
golang.org/x/exp v0.0.0-20180807140117-3d87b88a115f/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
golang.org/x/exp v0.0.0-20190125153040-c74c464bbbf2/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
@ -127,11 +129,18 @@ golang.org/x/image v0.0.0-20210216034530-4410531fe030 h1:lP9pYkih3DUSC641giIXa2X
golang.org/x/image v0.0.0-20210216034530-4410531fe030/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
golang.org/x/mobile v0.0.0-20190719004257-d2bd2a29d028/go.mod h1:E/iHnbuqvinMTCcRqshq8CkpyQDoeVncDDYHnLhea+o=
golang.org/x/mod v0.1.0/go.mod h1:0QHyrYULN0/3qlju5TqG8bIK38QM8yzMo5ekMj3DlcY=
golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
golang.org/x/mod v0.7.0 h1:LapD9S96VoQRhi/GrNTqeBJFrUjs5UHCAtTlgwA5oZA=
golang.org/x/mod v0.7.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
golang.org/x/net v0.0.0-20200904194848-62affa334b73/go.mod h1:/O7V0waA8r7cgGh81Ro3o1hOxt32SMVPicZroKQ2sZA=
golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
golang.org/x/net v0.5.0/go.mod h1:DivGGAXEgPSlEBzxGzZI+ZLohi+xUj054jfeKui00ws=
golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
@ -141,15 +150,28 @@ golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7w
golang.org/x/sys v0.0.0-20210304124612-50617c2ba197/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/sys v0.0.0-20210909193231-528a39cd75f3/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/sys v0.4.0 h1:Zr2JFtRQNX3BCZ8YtxRE9hNJYC8J6I1MVbMg6owUp18=
golang.org/x/sys v0.4.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
golang.org/x/term v0.4.0/go.mod h1:9P2UbLfCdcvo3p/nzKvsmas4TnlujnuoV9hGgYzW1lQ=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
golang.org/x/text v0.3.5 h1:i6eZZ+zk0SOf0xgBpEpPD18qWcJda6q1sxt3S0kzyUQ=
golang.org/x/text v0.3.5/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
golang.org/x/text v0.6.0 h1:3XmdazWV+ubf7QgHSTWeykHOci5oeekaGJBLkrkaw4k=
golang.org/x/text v0.6.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
golang.org/x/tools v0.0.0-20180525024113-a5b4c53f6e8b/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
golang.org/x/tools v0.0.0-20190206041539-40960b6deb8e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
golang.org/x/tools v0.0.0-20190927191325-030b2cf1153e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
golang.org/x/tools v0.5.0 h1:+bSpV5HIeWkuvgaMfI3UmKRThoTA5ODJTUd8T17NO+4=
golang.org/x/tools v0.5.0/go.mod h1:N+Kgy78s5I24c24dU8OfWNEotWjutIs8SnJvn5IDq+k=
golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=