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https://github.com/vsariola/sointu.git
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adcf3ebce8
send targets are now by ID and Song has "Score" part, which is the notes for it. also, moved the model part separate of the actual gioui dependend stuff. sorry to my future self about the code bomb; ended up too far and did not find an easy way to rewrite the history to make the steps smaller, so in the end, just squashed everything.
61 lines
2.1 KiB
Go
61 lines
2.1 KiB
Go
package tracker
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import (
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"math"
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)
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// Volume represents an average and peak volume measurement, in decibels. 0 dB =
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// signal level of +-1.
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type Volume struct {
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Average [2]float32
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Peak [2]float32
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}
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// VuAnalyzer receives stereo from the bc channel and converts these into peak &
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// average volume measurements, and pushes Volume values into the vc channel.
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// The pushes are nonblocking so if e.g. a GUI does not have enough time to
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// process redraw the volume meter, the values is just skipped. Thus, the vc
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// chan should have a capacity of at least 1 (!).
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//
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// Internally, it first converts the signal to decibels (0 dB = +-1). Then, the
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// average volume level is computed by smoothing the decibel values with a
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// exponentially decaying average, with a time constant tau (in seconds).
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// Typical value could be 0.3 (seconds).
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//
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// Peak volume detection is similar exponential smoothing, but the time
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// constants for attack and release are different. Generally attack << release.
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// Typical values could be attack 1.5e-3 and release 1.5 (seconds)
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//
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// minVolume is just a hard limit for the vuanalyzer volumes, in decibels, just to
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// prevent negative infinities for volumes
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func VuAnalyzer(tau float64, attack float64, release float64, minVolume float32, bc <-chan []float32, vc chan<- Volume) {
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v := Volume{Average: [2]float32{minVolume, minVolume}, Peak: [2]float32{minVolume, minVolume}}
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alpha := 1 - float32(math.Exp(-1.0/(tau*44100))) // from https://en.wikipedia.org/wiki/Exponential_smoothing
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alphaAttack := 1 - float32(math.Exp(-1.0/(attack*44100)))
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alphaRelease := 1 - float32(math.Exp(-1.0/(release*44100)))
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for buffer := range bc {
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for j := 0; j < 2; j++ {
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for i := 0; i < len(buffer); i += 2 {
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sample2 := float64(buffer[i+j] * buffer[i+j])
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if math.IsNaN(sample2) {
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sample2 = float64(minVolume)
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}
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dB := float32(10 * math.Log10(float64(sample2)))
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if dB < minVolume {
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dB = minVolume
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}
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v.Average[j] += (dB - v.Average[j]) * alpha
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alphaPeak := alphaAttack
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if dB < v.Peak[j] {
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alphaPeak = alphaRelease
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}
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v.Peak[j] += (dB - v.Peak[j]) * alphaPeak
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}
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}
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select {
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case vc <- v:
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default:
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}
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}
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}
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