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

[Cefn Hoile]

On 18 June 2012 16:27, Stefan Sauer <ensonic at hora-obscura.de> wrote:
> On 06/12/2012 04:25 PM, Cefn Hoile wrote:
>> On 12 June 2012 14:40, Stefan Sauer <ensonic at hora-obscura.de> wrote:
>>> 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
>>>> _______________________________________________
>>>> gstreamer-devel mailing list
>>>> gstreamer-devel at lists.freedesktop.org
>>>> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>>> _______________________________________________
>>> gstreamer-devel mailing list
>>> gstreamer-devel at lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>> Thanks for the suggestion, Stefan. You're right you can change it :)
>> Now I get regular lines which report -96 instead of -60 ...
>>
>> data: -96.0 -96.0 -96.0 -96.0 -96.0 -96.0 -96.0 -96.0
>>
>> My current pipeline looks like this...
>>
>> pulsesrc device="alsa_output.pci-0000_00_1b.0.analog-stereo.monitor" !
>> spectrum threshold=-96 interval=1000000000 bands=8 ! fakesink
>>
>> ...and still the DB levels never vary depending on output from the soundcard.
> Then I'd say there is a different problem. Are you sure you are
> monitoring the right monitor-port?
> Try gst-launch -e pulsesrc
> device="alsa_output.pci-0000_00_1b.0.analog-stereo.monitor" ! wavenc !
> filesink location=monitor.wav
> and check the resulting wav file.
>
> Stefan
>>
>> Cefn
>> http://cefn.com
>> _______________________________________________
>> gstreamer-devel mailing list
>> gstreamer-devel at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>
> _______________________________________________
> gstreamer-devel mailing list
> gstreamer-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel

Based on the results of the test you suggest, it is indeed silent. It
makes me think I must have the wrong audio device but then I don't
know what other choices I have. Does monitor need to be activated
somehow?

If I run the following to see all the possible names pulseaudio can
make sense of, I've tried all the values which appear and they all
produce silent .wav files. As you can see from the 'RUNNING' output
below, Gstreamer is able to activate the streams though.

pactl list short sources
0	alsa_output.pci-0000_01_00.1.hdmi-stereo.monitor	module-alsa-card.c	s16le
2ch 44100Hz	RUNNING
1	alsa_output.pci-0000_00_1b.0.analog-stereo.monitor	module-alsa-card.c	s16le
2ch 44100Hz	IDLE
2	alsa_input.pci-0000_00_1b.0.analog-stereo	module-alsa-card.c	s16le
2ch 44100Hz	SUSPENDED

Any ideas for something to try? I believe I have a stock build (had no
asound.conf or ~/asoundrc until just now when I was experimenting and
trying an alsa force-reload according to
https://wiki.archlinux.org/index.php/PulseAudio/Examples#ALSA_Monitor_source).