[PD] drop out problem

Andy Farnell padawan12 at obiwannabe.co.uk
Sat May 17 20:17:30 CEST 2008

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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Use the source

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