2 Dec
2023
2 Dec
'23
noon
Hi list,
I discovered that jackd can use different devices for input and output,
which is great! I am wondering if there will be the occasional click if
these two devices do not have synchronized word clocks? Or is there some
clever (resampling?) going on behind the scenes?
Thanks!
Peter
2 Dec
2 Dec
9:08 p.m.
I have always had good luck with jackd (specifically jack2) using two
soundcards for input and output with no perceivable clicks for me.
Another thing you can do as well is route your soundcard in with
pipewire-jack-bridge, like the pulseaudio bridge. In pipewire, all of
your soundcards will show up in the pipewire patchbay, and using
something like qpwgraph, you can then choose which soundcard you want to
pipe into jack.
Having said all of this, pipewire-jack (the replacement for jack) allows
you to route sound to whichever soundcard you would like, or even
multiple soundcards, and it has gotten really good as of late. I have
been playing around with it, but have yet to switch off of jackd for
pro-audio needs, but it is really enticing.
As far as the methods of doing this behind the scenes, I will defer to
someone else on here for that, I don't know but it's witchcraft for
sure. :) I hope it all continues to improve, it makes me really happy. :)
On 12/2/23 6:00 AM, Peter P. wrote:
Hi list,
I discovered that jackd can use different devices for input and output,
which is great! I am wondering if there will be the occasional click if
these two devices do not have synchronized word clocks? Or is there some
clever (resampling?) going on behind the scenes?
Thanks!
Peter
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3 Dec
3 Dec
6:09 p.m.
Thanks Brandon,
I am trying to stay clear of pipewire and stick to jack-only. Waiting
for insight into that witchcraft along with you.
:)
P
* Brandon Hale <bthaleproductions(a)gmail.com> [2023-12-02 21:08]:
I have always had good luck with jackd (specifically
jack2) using two
soundcards for input and output with no perceivable clicks for me.
Another thing you can do as well is route your soundcard in with
pipewire-jack-bridge, like the pulseaudio bridge. In pipewire, all of your
soundcards will show up in the pipewire patchbay, and using something like
qpwgraph, you can then choose which soundcard you want to pipe into jack.
Having said all of this, pipewire-jack (the replacement for jack) allows you
to route sound to whichever soundcard you would like, or even multiple
soundcards, and it has gotten really good as of late. I have been playing
around with it, but have yet to switch off of jackd for pro-audio needs, but
it is really enticing.
As far as the methods of doing this behind the scenes, I will defer to
someone else on here for that, I don't know but it's witchcraft for sure. :)
I hope it all continues to improve, it makes me really happy. :)
On 12/2/23 6:00 AM, Peter P. wrote:
Hi list,
I discovered that jackd can use different devices for input and output,
which is great! I am wondering if there will be the occasional click if
these two devices do not have synchronized word clocks? Or is there some
clever (resampling?) going on behind the scenes?
Thanks!
Peter
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7:02 p.m.
"Peter P." <peterparker(a)fastmail.com> writes:
Thanks Brandon,
I am trying to stay clear of pipewire and stick to jack-only. Waiting
for insight into that witchcraft along with you.
:)
I've just removed Pipewire from my system (Ubuntu Studio) and replaced
it with the Pulseaudio setup because I was unable to start Ardour with
my AC97 laptop on a session recorded with 96kHz sample frequency:
pipewire probably emulates an 48k Jack session and Ardour doesn't ask
about the audio but just asks me whether it should convert the session
to 48k.
Pulseaudio is a heap of something but it is a heap that knows when to
keep out of my way by now.
For normal desktop use, Pipewire appears to work but it appears
unwilling to tolerate other players by its side.
--
David Kastrup
4 Dec
4 Dec
4:24 a.m.
On Sat, 2 Dec 2023, Peter P. wrote:
I discovered that jackd can use different devices for
input and output,
which is great! I am wondering if there will be the occasional click if
these two devices do not have synchronized word clocks? Or is there some
clever (resampling?) going on behind the scenes?
No resampling, some internal sound cards use different devices for input
and output but are synced anyway. For example internal speakers and
external mic or HDMI anything. If you wish to use two unsynced devices use
the more important one as your jack master and then use alsa_in or
alsa_out for the other (alsa_in/out comes with jackd) or use zita-ajbridge
for better quality.
--
Len Ovens
www.ovenwerks.net
11:32 a.m.
Thanks Len,
in my case I am using my laptop's HDMI as output and the built-in
HDAIntel card as input. Do you know if there's a way to tell if they are
synced internally or will I have to test and wait for the occasional
click?
Thanks again,
Peter
* Len Ovens <len(a)ovenwerks.net> [2023-12-04 04:31]:
On Sat, 2 Dec 2023, Peter P. wrote:
I discovered that jackd can use different devices
for input and output,
which is great! I am wondering if there will be the occasional click if
these two devices do not have synchronized word clocks? Or is there some
clever (resampling?) going on behind the scenes?
No resampling, some internal sound cards use different devices for input and
output but are synced anyway. For example internal speakers and external mic
or HDMI anything. If you wish to use two unsynced devices use the more
important one as your jack master and then use alsa_in or alsa_out for the
other (alsa_in/out comes with jackd) or use zita-ajbridge for better
quality.
--
Len Ovens
www.ovenwerks.net
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2:21 p.m.
They are not synced.
No HDA nor HDMI audio devices offer any mechanism for sync.
On Mon, Dec 4, 2023 at 3:32 AM Peter P. <peterparker(a)fastmail.com> wrote:
Thanks Len,
in my case I am using my laptop's HDMI as output and the built-in
HDAIntel card as input. Do you know if there's a way to tell if they are
synced internally or will I have to test and wait for the occasional
click?
Thanks again,
Peter
* Len Ovens <len(a)ovenwerks.net> [2023-12-04 04:31]:
and
On Sat, 2 Dec 2023, Peter P. wrote:
> I discovered that jackd can use different devices for input and output,
> which is great! I am wondering if there will be the occasional click if
> these two devices do not have synchronized word clocks? Or is there
some
clever
(resampling?) going on behind the scenes?
No resampling, some internal sound cards use different devices for input output but are synced anyway. For example
internal speakers and external
mic
or HDMI anything. If you wish to use two unsynced
devices use the more
important one as your jack master and then use alsa_in or alsa_out for
the
other (alsa_in/out comes with jackd) or use
zita-ajbridge for better
quality.
--
Len Ovens
www.ovenwerks.net
_______________________________________________
Linux-audio-user mailing list -- linux-audio-user(a)lists.linuxaudio.org
To unsubscribe send an email to
linux-audio-user-leave(a)lists.linuxaudio.org
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To unsubscribe send an email to
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2:42 p.m.
* Paul Davis <paul(a)linuxaudiosystems.com> [2023-12-04 14:21]:
They are not synced.
No HDA nor HDMI audio devices offer any mechanism for sync.
Thanks Paul for clarifying this, much appreciated! is there a way to
tell which of the two will eventually skip samples? Or would it simply be the
one card whose word clock is slightly late (which I can't really
measure)? Would such a drop-out be reported by jackd(2) in its
"messages"?
Thanks again!
Peter
9:59 p.m.
On 5/12/23 00:42, Peter P. wrote:
* Paul Davis <paul(a)linuxaudiosystems.com>
[2023-12-04 14:21]:
Does it even matter if one is input and one is output?
The only situation I can imagine sync would be important is if you are
using separate cards to have extra channels for recording.
They are not synced.
No HDA nor HDMI audio devices offer any mechanism for sync.
Thanks Paul for
clarifying this, much appreciated! is there a way to
tell which of the two will eventually skip samples? Or would it simply be the
one card whose word clock is slightly late (which I can't really
measure)? Would such a drop-out be reported by jackd(2) in its
"messages"?
10:22 p.m.
On 2023-12-04 12:59, Roger wrote:
On 5/12/23 00:42, Peter P. wrote:
If Jack is syncing from the output device and has an xrun on the
input... you record that xrun. Depending on where your recording is
going, demo to show the band what it sounds like may not matter but song
to distribute you want zero xruns.
While it is true that HDA does not (the docs say it does but it
"sloppy", not a hard lock) support for sync, many mother board audio
systems split their internal audio into more than one device which
should mean they are not synced but because they are cheap they all use
the same clock anyway. However, in the case of hdmi, which is always 48k
SR, it always has it's own clock so this can be enforced.
So use your input as jack master and alsa_out for your hdmi. You want
your input to be jack master because you are recording it and you
probably don't want that going through SRC if it can be avoided. Output
doesn't matter till you do mixdown... then use it as jack master. That
is restart jack for mixing. I personally have not had success getting
HDMI to work with reasonable latency but that may not matter for most
recording.
--
Len Ovens
www.OvenWerks.net
* Paul Davis <paul(a)linuxaudiosystems.com>
[2023-12-04 14:21]:
Does it even matter if one is input and one is output?
The only situation I can imagine sync would be important is if you are
using
separate cards to have extra channels for recording. They are not synced.
No HDA nor HDMI audio devices offer any mechanism for sync.
Thanks Paul for
clarifying this, much appreciated! is there a way to
tell which of the two will eventually skip samples? Or would it simply
be the
one card whose word clock is slightly late (which I can't really
measure)? Would such a drop-out be reported by jackd(2) in its
"messages"? 
10:57 p.m.
On Mon, Dec 04, 2023 at 01:22:12PM -0800, Len Ovens wrote:
If Jack is syncing from the output device and has an
xrun on the input...
you record that xrun. Depending on where your recording is going, demo to
show the band what it sounds like may not matter but song to distribute you
want zero xruns.
It's some time since I looked at the code, but AFAIK Jack's ALSA backend
will wait for both input and output to be ready to provide/accept a
period of samples.
Then there is a difference between Jack1 and Jack2:
Jack1 will read the input at the start of a period, then call all
clients, and when all are done write to the output.
Jack2 (without -S) will read the input and write the output of the
previous period at the start a period, then run all clients.
With -S it behaves as Jack1.
So there are 4 cases to consider:
Jack1 or Jack2
Input is slower or output is slower.
At this time of day (22:55) I'm not going to torture my brain
to find out what would happen in each of these cases. But it's
certainly an interesting exercise, maybe it will appear in
my dreams tonight.
Anyway if the two devices don't have coherent sample rates,
just use zita-a2j/j2a. Of course you could use the input as
master when recording, and the output when mixing. But in
practice it wouldn't matter at all - there is no loss of
'quality' when the resampling is done the right way.
Ciao,
--
FA
5 Dec
5 Dec
12:52 p.m.
* Len Ovens <len(a)ovenwerks.net> [2023-12-04 22:22]:
[...]
So use your input as jack master and alsa_out for your
hdmi. You want your
input to be jack master because you are recording it and you probably don't
want that going through SRC if it can be avoided. Output doesn't matter till
you do mixdown... then use it as jack master. That is restart jack for
[...]
Thanks Len, how would I specify input or output as jack "master"?
Currently I simply select the two different interfaces in qjackctl.
cheersz, P
12:54 p.m.
* Peter P. <peterparker(a)fastmail.com> [2023-12-05 12:52]:
* Len Ovens <len(a)ovenwerks.net> [2023-12-04
22:22]:
[...]
Oh sorry, and I am running jackd2 here...
So use your input as jack master and alsa_out for
your hdmi. You want your
input to be jack master because you are recording it and you probably don't
want that going through SRC if it can be avoided. Output doesn't matter till
you do mixdown... then use it as jack master. That is restart jack for
[...]
Thanks Len, how would I specify input or output as jack "master"?
Currently I simply select the two different interfaces in qjackctl. 
6 Dec
6 Dec
3:46 a.m.
On Tuesday, December 5, 2023 5:52:22 AM CST Peter P. wrote:
how would I specify input or output as jack
"master"?
The design of jackd assumes devices share a clock, so the proper way is to
select the same device for input and output, then configure the second device
either using jackd command line parameters to configure the resampling internal
client, or start zita_a2j and zita_j2a as external clients.
--
Chris Caudle
424
days inactive
428
days old
linux-audio-user@lists.linuxaudio.org
13 comments
8 participants
participants (8)
-
Brandon Hale -
Chris Caudle -
David Kastrup -
Fons Adriaensen -
Len Ovens -
Paul Davis -
Peter P. -
Roger