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Re: LF: Octo-soundcard for the Raspi, another question

To: [email protected]
Subject: Re: LF: Octo-soundcard for the Raspi, another question
From: DK7FC <[email protected]>
Date: Thu, 06 Jul 2017 20:45:45 +0200
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Hi Paul,

Thanks for the quick reply. Thanks for the hint regarding @raw:1,2,3. That will further help to reduce the CPU load. So you seem to confirm that the CPU usage is normal for what i have done. I don't think that one of the channels are clipping but i will investigate. in SpecLab it show at -50 dB full scale, and the signal on CH1 is exactly the same as on CH2. The gain (alsamixer) is equal on all channels.
More later.

BTW there are local thunderstorm in quite a short distance. You asked for some a few months ago :-) I'm listening to them on VLF, using vlfrx tools for the first time to listen to my stream from the tree using wget | vtvorbis @vlf and then vtfilter @vlf | vtraw | aplay...
73, Stefan

Am 06.07.2017 20:13, schrieb Paul Nicholson:
Stefan wrote:

> the CPU load of vttime and vtresample increases continuously to
> very high values,

Yes, vttime will be using most of a core, @raw is 8 channels and
it's having to do a high quality resampling on them all.  If you
only want 3 channels, use @raw:1,2,3 for input to vttime.

vtresample we can't do much about, it already defaults to the lowest
quality setting.

> strangely the process number of vtwrite is lower than vtresample,
> although vtresample has been started earlier.

This is often the case when commands are run with -B option to
put them into background.  Each command forks twice to detach
itself from the controlling terminal.  When a pipeline is starting
up, it's a race to claim process IDs as they're all forking.

> channel 1 seems to show some minor glitches, see attachment.

Looks bad.   Run the signal through vtstat -i to see
if channel one is clipping at all.

  vtread ... | vtstat -i

Maybe both channels are close to hitting 1.0 amplitude in
the stream and ch1 is slightly higher gain.  You need to
look out for clipping if using integer sample formats.

> had to call the vlfrx tools from /usr/local/bin into that
> script

As Jacek says.   cron runs its commands with quite a minimal
enviroment, not quite the same as a login shell. For example it
doesn't run .bashrc as would a login shell so any extensions
to PATH or aliases wont be available unless you put them
in the crontab or in the scripts run by cron.

Paul Nicholson

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