[pulseaudio-discuss] Monitoring and Pulseaudio accuracy

Neil Wilson neil at aldur.co.uk
Mon Nov 30 02:33:26 PST 2009

Hi all,

I have pulseaudio running on Ubuntu and send the sound digitally to a
set of High end digital speakers. Since it is Hi-Fi, the work I'm
doing involves ensuring wherever possible that the digital bits are
not disturbed by the software systems the value is passing through -
unless it has to be when the softphone rings.

I did a simple test using pacat and parecord on the sink Monitor with
a set of float32le tones representing a simple log sweep through the
frequency range. Volumes were set to 100% across the entire chain. Yet
when I checked the float values, they had been perturbed by a small

That got me thinking. Can pulseaudio maintain a 'clean path'
throughout the entire software chain?

I'm presuming that some sort of rounding or conversion internally has
altered the float32le. Is there a representation that would be more
likely to come through 'clean'?

Additionally when I was doing a parec on the Monitor and used the
'float32ne' format it seemed to come out Big Endian on an Intel
machine, which surprised me a little. Is that a bug or did I miss


Neil Wilson

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