signal silence change detection

[enrike]

hi

Sorry if this question is too simple but I would like to analyse the
sound input and trigger a function when the amplitude rises above a
threshold. I need to detect changes between signal and silence.

I have done this in Supercollider with a DetectSilence which takes level
and falltime as arguments but I would like to see if there is an easy
way in Python to achieve the same.
http://doc.sccode.org/Classes/DetectSilence.html

I have been checking Follower but I dont understand very well how to use
it for my purposes

thanks

enrike

[barmin]

Hi Enrike,

What you need is a Trigger (http://ajaxsoundstudio.com/pyodoc/api/classes/triggers.html).

Try something like:

[code]

def silence_detected():
print "Silence detected!"


src = Input(0)
env = Follower(src)
th = Thresh(env, .5, dir=1)
tf = TrigFunc(th, silence_detected)

s.gui(locals())

[/code]

Hope this helps,

Matthieu

[enrike]

thanks!

[barmin]

... although I'm not sure how to replicate the "time" argument in http://doc.sccode.org/Classes/DetectSilence.html.

Anyone knows how to trigger a function only if the triggering condition holds for longer than a given time?

Matthieu

[Olivier Bélanger]

Hi,

Here is a class that acts like SC's DetectSilence:

#!/usr/bin/env python
# encoding: utf-8
from pyo import *

s = Server().boot()

class DetectSilence:
    def __init__(self, input, thresh=0.001, time=0.1, callback=None):
        self.input = input
        self.thresh = thresh
        self.callback = callback
        # little bit tricky just to get the sampling rate!
        sr = input.getBaseObjects()[0].getServer().getSamplingRate()
        # waiting time in samples
        timeInSamps = int(time * sr)
        # envelope follower
        self.follow = Follower(self.input)
        # if follower is below threshold, self.gate holds 1, as audio
        # stream. Otherwise it holds 0
        self.gate = self.follow < self.thresh
        # send a trigger to reset the counter on both threshold crossing
        self.reset = Select(self.gate, value=[0,1]).mix(1)
        self.count = Count(self.reset)
        # if the count reach timeInSamps while the gate holds 1 (below
        # threshold), send a trigger to call self.detected method
        self.trig = Select(self.count, value=timeInSamps, mul=self.gate)
        self.func = TrigFunc(self.trig, self.detected)

    def detected(self):
        # if callback is defined, call it
        if self.callback != None:
            self.callback()
        # otherwise just print to the console
        else:
            print "Silence detected!"


# play the table once...
t = SndTable(SNDS_PATH+"/transparent.aif")
src = TableRead(t, t.getRate()).out()
#src = Input(0)

# callback on detected silence
def replay():
    src.out()

silence = DetectSilence(src, thresh=0.001, time=0.1, callback=replay)

s.gui(locals())

Olivier

Matthieu

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[enrike]

thanks!


or., 2015.eko urtren 30a 17:20(e)an, Olivier Bélanger igorleak idatzi zuen:

> <mailto:bar...@bluewin.ch>>:

>
> ... although I'm not sure how to replicate the "time" argument in

> http://doc.sccode.org/Classes/__DetectSilence.html
> <http://doc.sccode.org/Classes/DetectSilence.html>.

>
> Anyone knows how to trigger a function only if the triggering
> condition holds for longer than a given time?
>
>
> Matthieu
>
> --
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[barmin]

Now I understand why I couldn't see how to do it ;-)

Thanks Olivier!

[Olivier Bélanger]

Yep, that was not an easy one! Maybe, it should be a single object...

Olivier

[barmin]

You've made so many things so easy with pyo that I cannot help thinking this should be easier than that. I guess I'm a spolied brat ;-)

But wait... if I understand you solution correctly, it should be relatively easy to make a generic Trigger out of it. Something like

trig = Holds(cond=follow<thresh, time=0.1)

Any chance something like that would be included in a next version of pyo?

Matthieu

Le 30. 01. 15 18:12, Olivier Bélanger a écrit :

> Yep, that was not an easy one! Maybe, it should be a single object...
>
> Olivier
>
>

> 2015-01-30 11:31 GMT-05:00 barmin <bar...@bluewin.ch <mailto:bar...@bluewin.ch>>: