Re: [LAD] JACK and ALSA elucidations

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To: Gianfranco Ceccolini <gianfranco@...>
Cc: linux-audio-dev@lists.linuxaudio.org <linux-audio-dev@...>
Date: Friday, February 28, 2014 - 6:12 pm

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On Fri, Feb 28, 2014 at 12:57 PM, Gianfranco Ceccolini <
gianfranco@portalmod.com.br> wrote:

>

these are the number of "segments" or "periods" that the h/w buffer is
divided into. Input latency is determined by period size, playback latency
is determined by buffer size. the device will wake the CPU every time it
has 1 period of date/space available.

>

JACK starts in realtime mode by default. It can be "forced" to do that with
-R or you can turn it off with -r.

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On Fri, Feb 28, 2014 at 12:57 PM, Gianfranco Ceccolini <=
gianfranco@portalmod.com.br
> wrote:

creating alsa driver ... hw:0|hw:0|128|2|48000|0|0|=
nomon|swmeter|-|32bit
configuring for 48000Hz, period =3D 128 frames (2.7=
ms), buffer =3D 2 periods
ALSA: final selected sample format for capture: 32b=
it integer little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 32=
bit integer little-endian
ALSA: use 2 periods for playbackWhen starting it on the Beaglebone Black I get:

/usr/bin/jackd --realtime -P80 -dalsa -r48000 -p128=
-n2 -Xrawc=
reating alsa driver ... hw:0|hw:0|128|2|48000|0|0|nomon|swmeter|-|32bit=

configuring for 48000Hz, period =3D 128 frames (2.7 ms), buffer =3D 2 perio=
dsALSA: final selected sample format for captur=
e: 32bit integer little-endianALSA: use 16 peri=
ods for capture

ALSA: final selected sample format for playback: 32=
bit integer little-endianALSA: use 16 periods f=
or playback- what are those "pe=
riods" in the ALSA lines? (2 for the PC and 16 for the BBB) ?
these are the number of "segmen=
ts" or "periods" that the h/w buffer is divided into. Input =
latency is determined by period size, playback latency is determined by buf=
fer size. the device will wake the CPU every time it has 1 period of date/s=
pace available.
=A0- o=
n the ArchWiki page on Jack there is a D-bus call

jack_control eps r=
ealtime truestating that it "Sets JACK to=
realtime mode in its own internal setup."

What is this internal setup? How do I address this when no=
t using D-Bus?JACK star=
ts in realtime mode by default. It can be "forced" to do that wit=
h -R or you can turn it off with -r.
=A0

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Messages in current thread:
[LAD] JACK and ALSA elucidations, Gianfranco Ceccolini, (Fri Feb 28, 5:58 pm)
Re: [LAD] JACK and ALSA elucidations, Jeremy Jongepier, (Fri Feb 28, 8:01 pm)
Re: [LAD] JACK and ALSA elucidations, Gianfranco Ceccolini, (Mon Mar 10, 1:51 pm)
Re: [LAD] JACK and ALSA elucidations, Alex Gagnon, (Mon Mar 10, 2:34 pm)
Re: [LAD] JACK and ALSA elucidations, Paul Davis, (Mon Mar 10, 2:50 pm)
Re: [LAD] JACK and ALSA elucidations, Paul Davis, (Mon Mar 10, 2:26 pm)
Re: [LAD] JACK and ALSA elucidations, Gianfranco Ceccolini, (Wed Mar 12, 2:26 am)
Re: [LAD] JACK and ALSA elucidations, Paul Davis, (Wed Mar 12, 2:50 am)
Re: [LAD] JACK and ALSA elucidations, Gianfranco Ceccolini, (Wed Mar 12, 3:21 am)
Re: [LAD] JACK and ALSA elucidations, Paul Davis, (Wed Mar 12, 12:12 pm)
Re: [LAD] JACK and ALSA elucidations, Jeremy Jongepier, (Wed Mar 12, 11:37 am)
Re: [LAD] JACK and ALSA elucidations, Paul Davis, (Fri Feb 28, 6:12 pm)