[LAU] Record levels lower in Alsa than Jack

John Murphy rosegardener at freeode.co.uk
Fri Nov 6 14:22:42 CET 2020

On Fri, 6 Nov 2020 12:16:05 +0100 Fons Adriaensen wrote:
> On Fri, Nov 06, 2020 at 10:55:38AM +0000, John Murphy wrote:
> > You'll understand I'd rather use jack if possible. :)  
> Of course, but even then you'd have to get PA out of the way.
> One way would be to configure PA to not use the sound card
> you want to use with Jack. See PA docs :-)

It's usually just set 'off' in PAVolumeControl. Seems to stay that way.
Pulse gets to use the onboard soundcard. The line out is connected
to an input on the USB interface. VLC, firefox etc. are happy.

I think I've discovered where my levels were going awry. I was using
timemachine to record in w64 format and converting to wav. Now, using:

jack_capture -s --channels 2 --port system:capture* -d 10 -f w64 t1w64.w64 \
& jack_capture -s --channels 2 --port system:capture* -d 10 -f wav t1wav.wav


sox --no-clobber -S t1w64.w64 -b 16 t2wav.wav

Then sox stat shows min/max amplitude +/- 0.5 for the wav capture and
+/- 0.9 for the wav converted from w64. The converted file looks good
in my editor too.

Thanks again,

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