[PD] Re: [PD-announce] Pd 0.39 test 5 released

Tim Blechmann TimBlechmann at gmx.net
Mon Aug 22 12:11:30 CEST 2005

> I tried to calculate the latency of my system summing up all
> pd-buffers,  driver buffers, DACs and ADCs latency (given by the
> manufactorer) but,  compared to the measured latency (analog
> loop-back) I get a difference  of ~1.5ms (@fs=48kHz). Thus, I wonder
> what do I wrong and how to  calculate which latency of a system which
> predicts the correct  measurable latency.
hm ... i've never done the actual calculations ... but one piece of
hardware that has to be taken into account is the pci bus / cardbus
bridge ... but this should be reported by the driver ...

the additional latency might result from miller's synchronous
scheduler ... instead of using the hardware interrupt to run the dsp
(the way devel_0_39 can operate), the dsp scheduler independently from
the hardware ... in theory, this would result in one blocksize of
latency ... about 1.3ms at 48kHz ...

currently the scheduler that's run by a driver callback at interrupt
time is only implemented for portaudio, native asio and jack (although
jack adds some additional latency)

cheers ... tim

mailto:TimBlechmann at gmx.de    ICQ: 96771783

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