[PD] precision of vline~ and/or pd messaging

João Pais jmmmpais at googlemail.com
Wed Jan 25 00:53:43 CET 2012

Hmm, I have to correct your message to get a more interesting answer from  
you :)

the SR is 48K, and I'm using vline~ already. Theoretically with E Lyon's  
objects I should also get more messaging precision, or maybe not at all?


> I'm not sure if this is correct, so someone with a deeper knowledge of  
> Pd can confirm/deny... :)
> 125ms at a samplerate of (I'm guessing) 44100 would mean you're sending  
> a message to [line~]
> every 5512.5 samples.  Pd's default blocksize is 64, and when you  
> convert from a control value to
> a signal value using the [line~] method then you are forced to start/end  
> the ramp on block boundaries.
> Since 64 does not divide into 5512.5 evenly then there is no way you can  
> perfectly recreate the
> sine tone using this method.  (I haven't looked at your example but I  
> would imagine that [line~]
> forces the "remainder" to occur over the course of an entire blockthus  
> stretching out that part of
> your sine wave to be longer than you want.)
> You could recreate it using [vline~] however, because it will let you  
> start/end a ramp in the middle of
> a block, thus giving you higher precision (presumably at a higher CPU  
> cost).
> -Jonathan
>> ________________________________
>> From: João Pais <jmmmpais at googlemail.com>
>> To: PD-List <pd-list at iem.at>
>> Sent: Tuesday, January 24, 2012 4:50 PM
>> Subject: [PD] precision of vline~ and/or pd messaging
>> Hi,
>> please look at the attached audio file. It's a recording of a sinus  
>> tone stored in an array, played back with consecutive segments of  
>> 125ms. If you look at each multiple of 125ms, you'll see there's a  
>> glitch in the waveform. That means, the pd patch isn't fully precise  
>> aliging the several fragments together. Or maybe the messaging isn't  
>> precisely aligned with the audio.
>> For this patch I'm using E Lyon's samm~ and click2bang~ to send the  
>> messages, theoretically to have greater precision - and then some  
>> counters and table readers make several calculations to get the indexes  
>> of the segments. After these message-level calculations, the data goes  
>> to vline~ reading from a tabread4~.
>> My question is then: is it possible to get messaging and audio in Pd  
>> ligned up, so that the resulting audio file is as precise as an  
>> original osc~? If so, which objects or parameters should be used  
>> instead?
>> Thanks,
>> Joao
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