[PD] drop out problem

Roman Haefeli reduzierer at yahoo.de
Sat May 17 21:19:50 CEST 2008


what do you consider many? i counted 8 [line~]s and 4 [vline~]s in the
main patch. the main patch is using 10 instances of an abstraction, that
has a [line~], so the sum of all is around 22 [line~] objects. 

i could narrow it a little bit down. i replaced the tracker patch by a
dummy data sending patch and indeed:

if i send the same message to the audio patch with  a constant rate
(16.66ms, respectively 60Hz), there are no dropouts. now, if i alternate
between two different messages at the same rate, the audio patch just
keeps stuttering, while the cpu load increases from 55% to ~70%. 

i also tried a much lower rate: 100ms (10Hz) and 200ms (5Hz) and even
with 5 messages per second, there are dropouts.... strange....

the same test on the other (slower) box doesn't cause any drop-outs.

i am a bit stumped.

roman




On Sat, 2008-05-17 at 19:17 +0100, Andy Farnell wrote:
> Roman, are you using many [line] objects to interpolate the
> incoming tracker data?
> 
> On Sat, 17 May 2008 20:08:26 +0200
> Roman Haefeli <reduzierer at yahoo.de> wrote:
> 
> > hi all
> > 
> > i am setting up a box for an installation. it runs two instances of pd:
> > 
> > audio:
> > pd -rt -jack (with only very few externals loaded)
> > 
> > tracking:
> > pd -nrt -noaudio (with quite a lot of externals loaded, such as Gem,
> > comport, wiimote and others).
> > 
> > both instances talk with each other over two [netsend]/[netreceive]
> > connections (one for each way). the main part of the tcp connection
> > bandwith is tracking data sent from the tracking patch to the audio
> > patch at fixed rate, where each message is 12 floats long. 
> > 
> > all that runs fine and smooth on my own mobile box:
> > pentium M 1.7GHz
> > 1.5GB RAM
> > ubuntu dapper
> > pd 0.40.3 over jack (48KHz, 1024 frames/period, 2 periods/buffer )
> > cpu usage is around 80%
> > 
> > the same two patches on the installation box cause lots of drop-outs:
> > AMD Athlon XP 2.8GHz
> > 512MB RAM
> > ubuntu gutsy with rt-kernel and everything setup for low-latency
> > pd 0.40.3 (with same jackd settings)
> > cpu usage around 60%
> > 
> > funny enough, that the much faster machine with the more appropriate
> > setup (rt-kernel) is having the drop-outs.
> > usually i would suspect [netsend] or [netreceive] to be the cause of the
> > problem. but in this case the data rate sent over the tcp socket is
> > constant, whereas the dropouts only happen, if the tracking data changes
> > values, but not, if the stream from the tracking patch keeps sending the
> > same values. the major part of the audio patch is just some synth stuff,
> > that is constantly running, so there aren't big jumps in cpu usage
> > expected. from what i can tell, the only thing, that happens in the
> > audio patch, when the received stream changes its values, is, that
> > around 10 [partconv~]  objects switch tables from a preloaded set of
> > around 1400 tables, where each table is 512 samples long. i don't have
> > an explanation, why this could affect audio (and why it doesn't on my
> > slower mobile box), but this is what i observed. i am happy with any
> > possible explanation of that behaviour and even more with an idea how to
> > solve it. i really would like to avoid not to have to use my personal
> > laptop for the installation.
> > 
> > roman
> > 
> >  
> > 
> > 
> > 
> > 		
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> 


		
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