Re: [Sndobj-devel] PySndObj: Problem with SndObj & time.sleep() -- making a metronome with SndObj

[todd i. <tes...@as...>]

Certainly you should not be getting the distorted sounds, but one  
other possibility to try that might be more solid would be to use  
SyncGrain to generate a "grain" (the beep) at some rate. i can't test  
it right now, but i would think that would work and would not rely on  
the time stuff in python.



On Jan 29, 2007, at 3:24 AM, Victor Lazzarini wrote:

> Instead of turning the thread on and off, you can try using
> SndObj::Disable()/Enable() to
> turn the processing of an object off  (outputs zero thereafter)/on.  
> Or you
> can use SetAmp(0) on the Oscili object that zeros the amplitude.
>
> Because there are two threads, timing might be slightly wobbly. If you
> need precision you can set a callback that calls either method.  
> This will
> be called from the processing thread, always before processing. The
> timing resolution then is however many samples your vector is (you
> can bring it down to 1 sample if you need).
>
> Callbacks for SndThread were introduced in the latest version (better
> get the latest CVS) and are documented in the latest reference manual.
> There are some examples of its use in the python subdir of the  
> sources.
>
> Victor
>
> At 05:55 29/01/2007, Craig Lewiston wrote:
>> One use of SndObj in my application is to provide the audio "beep"  
>> for
>> a metronome thread that executes alongside my main program loop (a
>> Tkinter GUI).  I figured the easiest way to go about this would be to
>> stick the following steps inside a loop:
>>
>> 1) turn the sound on,
>> 2) wait for the beep length (in this case 50 ms),
>> 3) turn the sound off,
>> 4) wait the remainder of time until the next beat.
>>
>> The four steps would reside inside a loop that executed for the
>> duration of the song.  However, working towards that end, I've found
>> that when i simply attempt to do the following (without putting it in
>> a loop):
>>
>> thread.ProcOn()
>> time.sleep(0.05)
>> thread.ProcOff()
>> time.sleep(0.45)
>>
>> I don't get the desired effect.  I want the sound on for 50 ms, and
>> then off for 450 ms.  Instead, with the above code, I get 50 ms of  
>> the
>> desired sound (a sine wave in this case), followed by 450 ms of a
>> distorted version of the sound.  It seems to be a weird interaction
>> between SndThread and time.sleep.
>>
>> When i do this:
>>
>> thread.ProcOn()
>> time.sleep(0.05)
>> thread.ProcOff()
>>
>> or this:
>>
>> thread.ProcOn()
>> time.sleep(0.05)
>>
>> I get the desired result: 50 ms of a sine wave.  (In the second case,
>> I really don't understand why it stops WITHOUT the thread.ProcOff()
>> statement, but that's not the issue here)
>>
>> if I do this:
>> thread.ProcOn()
>>
>> I get NO output, which is weird because i would expect it to just  
>> turn
>> the sound on and not turn it off until i hard-closed the Python
>> Interpreter.
>>
>> Here's the full code:
>> ------------------------------------
>> import sndobj
>> import time
>>
>> tab = sndobj.HarmTable(5000,2, 1)
>> osc = sndobj.Oscili(tab, 3000, 16000)
>> outp = sndobj.SndRTIO(1)
>> outp.SetOutput(1, osc)
>>
>> thread = sndobj.SndThread()
>> thread.AddObj(osc)
>> thread.AddObj(outp, sndobj.SNDIO_OUT)
>>
>> thread.ProcOn()
>> time.sleep(0.05)
>> thread.ProcOff()
>> time.sleep(0.45)
>> ------------------------------------
>> and my system specs: OSX 10.4.8, Powerbook G4, Python 2.4.4
>>
>>
>> So, I'm sorta at a loss for what to do.  I've gone through enough
>> trouble to get SndObj up and running (I was using tkSnack before
>> [http://www.speech.kth.se/snack/]), which gave me problems of its own
>> (intermittent playback quality).  I'm trying to figure out if I  
>> should
>> stick through with SndObj for realtime audio processing in my
>> application, or look for another module.
>>
>> Also, concerning the metronome problem, I was wondering if maybe the
>> better route to take, instead of creating a loop to start and stop  
>> the
>> sound, would be instead to create one metronome audio track that  
>> lasts
>> the length of the song, and then just play it at the beginning and
>> stop it at the end.
>>
>> Thoughts?
>>
>> Thanks,
>> Craig
>>
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>
> Victor Lazzarini
> Music Technology Laboratory
> Music Department
> National University of Ireland, Maynooth
>
>
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