Soundcard 'monitor' stream doesn't arrive with Spectrum plugin

[Stefan Sauer]

On 06/12/2012 04:13 AM, Cefn Hoile wrote:
> I'm hoping to base a tutorial demo on the first python example linked
> below, and I attempted to test its logic by playing music from
> Rhythmbox through my (Ubuntu Oneiric) soundcard while visualising the
> result of the 'spectrum' FFT as changing numbers streaming on the
> console. Sadly this first debugging step was a failure.
>
> http://pzwart3.wdka.hro.nl/wiki/Spectrum.py
>
> The spectrum plugin loaded by this python script only ever reports -60
> decibels for every frequency band in the spectrum, regardless how loud
> I turn up the music!
You can change that:
spectrum threshold=-96

Stefan
>
> I have tried both alsasrc and pulsesrc with various device names
> (default, pulse, the introspected alsa monitor device name from pactl)
> at the beginning of the listener_desc pipeline (declared in the linked
> code). In most of the cases I've tried (barring typos) the pipeline
> seems to be established and run perfectly fine (as far as I can tell)
> but somehow no sound frequencies show up in the frequency analysis
> from the spectrum plugin.
>
> Does this python code work for anyone else? How would I verify that
> the pipeline is correct, or narrow down the problem? Any suggestions
> what the initial source plugin or entire pipeline should in fact be on
> an Ubuntu system to get loudnesses per frequency range streaming out
> of the spectrum plugin to the console using this code as a reference?
>
> Thanks for any help.
>
> Cefn
> http://cefn.com
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