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https://github.com/vsariola/sointu.git
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cd700ed954
The RPC and sync library mechanisms were removed for now; they never really worked and contained several obvious bugs. Need to consider if syncs are useful at all during the compose time, or just used during intro.
63 lines
2.1 KiB
Go
63 lines
2.1 KiB
Go
package tracker
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import (
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"errors"
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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]float64
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Peak [2]float64
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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 (v *Volume) Analyze(buffer []float32, tau float64, attack float64, release float64, minVolume float64, maxVolume float64) error {
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alpha := 1 - math.Exp(-1.0/(tau*44100)) // from https://en.wikipedia.org/wiki/Exponential_smoothing
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alphaAttack := 1 - math.Exp(-1.0/(attack*44100))
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alphaRelease := 1 - math.Exp(-1.0/(release*44100))
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var err error
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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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if err == nil {
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err = errors.New("NaN detected in master output")
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}
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continue
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}
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dB := 10 * math.Log10(float64(sample2))
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if dB < minVolume || math.IsNaN(dB) {
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dB = minVolume
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}
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if dB > maxVolume {
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dB = maxVolume
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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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return err
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}
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