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stereo equalizer
plus examples of mono and stereo
This commit is contained in:
Craig Swank
@@ -16,11 +16,21 @@ type (
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}
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section struct {
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a, b []float64
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a, b [2][]float64
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xPast, yPast [][2]float64
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}
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EqualizerSection struct {
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// EqualizerSections is the interfacd that is passed into NewEqualizer
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EqualizerSections interface {
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sections(fs float64) []section
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}
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StereoEqualizerSection struct {
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Left MonoEqualizerSection
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Right MonoEqualizerSection
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}
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MonoEqualizerSection struct {
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// F0 (center frequency) sets the mid-point of the section’s
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// frequency range and is given in Hertz [Hz].
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F0 float64
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@@ -52,10 +62,90 @@ type (
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// cut (volume down) and positive numbers to boost (volume up).
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G float64
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}
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// StereoEqualizerSections implements EqualizerSections and can be passed into NewEqualizer
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StereoEqualizerSections []StereoEqualizerSection
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// MonoEqualizerSections implements EqualizerSections and can be passed into NewEqualizer
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MonoEqualizerSections []MonoEqualizerSection
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)
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func (s *section) apply(x [][2]float64) [][2]float64 {
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ord := len(s.a) - 1
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// NewEqualizer returns a beep.Streamer that modifies the stream based on the EqualizerSection slice that is passed in.
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// The SampleRate (sr) must match that of the Streamer.
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func NewEqualizer(st beep.Streamer, sr beep.SampleRate, s EqualizerSections) beep.Streamer {
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return &equalizer{
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streamer: st,
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sections: s.sections(float64(sr)),
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}
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}
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func (m MonoEqualizerSections) sections(fs float64) []section {
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out := make([]section, len(m))
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for i, s := range m {
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out[i] = s.section(fs)
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}
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return out
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}
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func (m StereoEqualizerSections) sections(fs float64) []section {
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out := make([]section, len(m))
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for i, s := range m {
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out[i] = s.section(fs)
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}
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return out
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}
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// Stream streams the wrapped Streamer modified by Equalizer.
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func (e *equalizer) Stream(samples [][2]float64) (n int, ok bool) {
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n, ok = e.streamer.Stream(samples)
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for _, s := range e.sections {
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s.apply(samples)
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}
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return n, ok
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}
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// Err propagates the wrapped Streamer's errors.
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func (e *equalizer) Err() error {
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return e.streamer.Err()
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}
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func (m MonoEqualizerSection) section(fs float64) section {
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beta := math.Tan(m.Bf/2.0*math.Pi/(fs/2.0)) *
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math.Sqrt(math.Abs(math.Pow(math.Pow(10, m.GB/20.0), 2.0)-
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math.Pow(math.Pow(10.0, m.G0/20.0), 2.0))) /
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math.Sqrt(math.Abs(math.Pow(math.Pow(10.0, m.G/20.0), 2.0)-
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math.Pow(math.Pow(10.0, m.GB/20.0), 2.0)))
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b := []float64{
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(math.Pow(10.0, m.G0/20.0) + math.Pow(10.0, m.G/20.0)*beta) / (1 + beta),
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(-2 * math.Pow(10.0, m.G0/20.0) * math.Cos(m.F0*math.Pi/(fs/2.0))) / (1 + beta),
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(math.Pow(10.0, m.G0/20) - math.Pow(10.0, m.G/20.0)*beta) / (1 + beta),
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}
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a := []float64{
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1.0,
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-2 * math.Cos(m.F0*math.Pi/(fs/2.0)) / (1 + beta),
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(1 - beta) / (1 + beta),
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}
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return section{
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a: [2][]float64{a, a},
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b: [2][]float64{b, b},
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}
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}
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func (s StereoEqualizerSection) section(fs float64) section {
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l := s.Left.section(fs)
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r := s.Right.section(fs)
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return section{
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a: [2][]float64{l.a[0], r.a[0]},
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b: [2][]float64{l.b[0], r.b[0]},
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}
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}
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func (s *section) apply(x [][2]float64) {
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ord := len(s.a[0]) - 1
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np := len(x) - 1
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if np < ord {
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@@ -65,85 +155,40 @@ func (s *section) apply(x [][2]float64) [][2]float64 {
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y := make([][2]float64, len(x))
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if len(s.xPast) == 0 {
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s.xPast = make([][2]float64, len(x))
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if len(s.xPast) < len(x) {
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s.xPast = append(s.xPast, make([][2]float64, len(x)-len(s.xPast))...)
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}
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if len(s.yPast) == 0 {
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s.yPast = make([][2]float64, len(x))
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if len(s.yPast) < len(x) {
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s.yPast = append(s.yPast, make([][2]float64, len(x)-len(s.yPast))...)
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}
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for i := 0; i < len(x); i++ {
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for j := 0; j < ord+1; j++ {
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if i-j < 0 {
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y[i][0] = y[i][0] + s.b[j]*s.xPast[len(s.xPast)-j][0]
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y[i][1] = y[i][1] + s.b[j]*s.xPast[len(s.xPast)-j][1]
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y[i][0] = y[i][0] + s.b[0][j]*s.xPast[len(s.xPast)-j][0]
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y[i][1] = y[i][1] + s.b[1][j]*s.xPast[len(s.xPast)-j][1]
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} else {
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y[i][0] = y[i][0] + s.b[j]*x[i-j][0]
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y[i][1] = y[i][1] + s.b[j]*x[i-j][1]
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y[i][0] = y[i][0] + s.b[0][j]*x[i-j][0]
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y[i][1] = y[i][1] + s.b[1][j]*x[i-j][1]
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}
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}
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for j := 0; j < ord; j++ {
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if i-j-1 < 0 {
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y[i][0] = y[i][0] - s.a[j+1]*s.yPast[len(s.yPast)-j-1][0]
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y[i][1] = y[i][1] - s.a[j+1]*s.yPast[len(s.yPast)-j-1][1]
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y[i][0] = y[i][0] - s.a[0][j+1]*s.yPast[len(s.yPast)-j-1][0]
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y[i][1] = y[i][1] - s.a[1][j+1]*s.yPast[len(s.yPast)-j-1][1]
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} else {
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y[i][0] = y[i][0] - s.a[j+1]*y[i-j-1][0]
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y[i][1] = y[i][1] - s.a[j+1]*y[i-j-1][1]
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y[i][0] = y[i][0] - s.a[0][j+1]*y[i-j-1][0]
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y[i][1] = y[i][1] - s.a[1][j+1]*y[i-j-1][1]
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}
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}
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y[i][0] = y[i][0] / s.a[0]
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y[i][1] = y[i][1] / s.a[0]
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y[i][0] = y[i][0] / s.a[0][0]
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y[i][1] = y[i][1] / s.a[1][0]
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}
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s.xPast = x
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s.yPast = y
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return y
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}
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// NewEqualizer returns a beep.Streamer that modifies the stream based on the EqualizerSection slice that is passed in.
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// The SampleRate (sr) must match that of the Streamer.
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func NewEqualizer(s beep.Streamer, sr beep.SampleRate, sections []EqualizerSection) beep.Streamer {
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fs := float64(sr)
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out := &equalizer{
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streamer: s,
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}
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for _, s := range sections {
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beta := math.Tan(s.Bf/2.0*math.Pi/(fs/2.0)) *
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math.Sqrt(math.Abs(math.Pow(math.Pow(10, s.GB/20.0), 2.0)-
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math.Pow(math.Pow(10.0, s.G0/20.0), 2.0))) /
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math.Sqrt(math.Abs(math.Pow(math.Pow(10.0, s.G/20.0), 2.0)-
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math.Pow(math.Pow(10.0, s.GB/20.0), 2.0)))
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b := []float64{
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(math.Pow(10.0, s.G0/20.0) + math.Pow(10.0, s.G/20.0)*beta) / (1 + beta),
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(-2 * math.Pow(10.0, s.G0/20.0) * math.Cos(s.F0*math.Pi/(fs/2.0))) / (1 + beta),
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(math.Pow(10.0, s.G0/20) - math.Pow(10.0, s.G/20.0)*beta) / (1 + beta),
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}
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a := []float64{
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1.0,
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-2 * math.Cos(s.F0*math.Pi/(fs/2.0)) / (1 + beta),
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(1 - beta) / (1 + beta),
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}
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out.sections = append(out.sections, section{a: a, b: b})
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}
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return out
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}
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// Stream streams the wrapped Streamer modified by Equalizer.
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func (e *equalizer) Stream(samples [][2]float64) (n int, ok bool) {
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n, ok = e.streamer.Stream(samples)
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for _, s := range e.sections {
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copy(samples, s.apply(samples))
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}
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return n, ok
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}
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// Err propagates the wrapped Streamer's errors.
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func (e *equalizer) Err() error {
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return e.streamer.Err()
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s.xPast = x[:]
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s.yPast = y[:]
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copy(x, y)
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}
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36
examples/tutorial/5-equalizer/mono/main.go
Normal file
36
examples/tutorial/5-equalizer/mono/main.go
Normal file
@@ -0,0 +1,36 @@
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package main
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import (
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"math/rand"
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"time"
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"github.com/faiface/beep"
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"github.com/faiface/beep/effects"
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"github.com/faiface/beep/speaker"
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)
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func noise() beep.Streamer {
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return beep.StreamerFunc(func(samples [][2]float64) (n int, ok bool) {
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for i := range samples {
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samples[i][0] = rand.Float64()*2 - 1
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samples[i][1] = rand.Float64()*2 - 1
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}
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return len(samples), true
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})
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}
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func main() {
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sr := beep.SampleRate(44100)
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speaker.Init(sr, sr.N(time.Second/10))
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eq := effects.NewEqualizer(noise(), sr, effects.MonoEqualizerSections{
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{F0: 200, Bf: 5, GB: 3, G0: 0, G: 8},
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{F0: 250, Bf: 5, GB: 3, G0: 0, G: 10},
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{F0: 300, Bf: 5, GB: 3, G0: 0, G: 12},
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{F0: 350, Bf: 5, GB: 3, G0: 0, G: 14},
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{F0: 10000, Bf: 8000, GB: 3, G0: 0, G: -100},
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})
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speaker.Play(eq)
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select {}
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}
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39
examples/tutorial/5-equalizer/stereo/main.go
Normal file
39
examples/tutorial/5-equalizer/stereo/main.go
Normal file
@@ -0,0 +1,39 @@
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package main
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import (
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"math/rand"
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"time"
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"github.com/faiface/beep"
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"github.com/faiface/beep/effects"
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"github.com/faiface/beep/speaker"
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)
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func noise() beep.Streamer {
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return beep.StreamerFunc(func(samples [][2]float64) (n int, ok bool) {
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for i := range samples {
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samples[i][0] = rand.Float64()*2 - 1
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samples[i][1] = rand.Float64()*2 - 1
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}
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return len(samples), true
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})
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}
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func main() {
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sr := beep.SampleRate(44100)
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speaker.Init(sr, sr.N(time.Second/10))
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eq := effects.NewEqualizer(noise(), sr, effects.StereoEqualizerSections{
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{
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Left: effects.MonoEqualizerSection{F0: 200, Bf: 5, GB: 3, G0: 0, G: 8},
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Right: effects.MonoEqualizerSection{F0: 200, Bf: 5, GB: 3, G0: 0, G: -8},
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},
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{
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Left: effects.MonoEqualizerSection{F0: 10000, Bf: 1000, GB: 3, G0: 0, G: 90},
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Right: effects.MonoEqualizerSection{F0: 10000, Bf: 1000, GB: 3, G0: 0, G: -90},
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},
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})
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speaker.Play(eq)
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select {}
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}
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