[LAU] (Ardour) How to get rid of delay when recording ?

[jonetsu at teksavvy.com]

On Sat, 13 Feb 2016 22:11:40 +0000
Harry van Haaren <harryhaaren at gmail.com> wrote:


> $ ps -eo rtprio,comm --sort -rtprio | head -n 30

This yields:

 RTPRIO COMMAND
    99 migration/0
    99 watchdog/0
    99 watchdog/1
    99 migration/1
    99 watchdog/2
    99 migration/2
    99 watchdog/3
    99 migration/3
    50 irq/52-mei_me
     - init
     - kthreadd
     - ksoftirqd/0
     - kworker/0:0H
     - rcu_sched
     - rcuos/0
     - rcuos/1
     - rcuos/2
     - rcuos/3
     - rcu_bh
     - rcuob/0
     - rcuob/1
     - rcuob/2
     - rcuob/3
     - ksoftirqd/1
     - kworker/1:0
     - kworker/1:0H
     - ksoftirqd/2
     - kworker/2:0
     - kworker/2:0H

> * Depends on soundcard, check output of
> $ cat /proc/interrupts  and find the interrupt for the Delta1010

From 'lspci' I got it that the 1010LT is ICE1712, then
/proc/interrupts is:

 18: 132417 52953 35846 25609 IR-IO-APIC-fasteoi snd_ice1712

> The important thing is the *order* of the tasks, *not* the number
> itself. They are serviced based on order, as fast as possible.

OK.
 
> *Always* run jackd as the user that you will be doing the sound
> processing as - do not run jackd as a system daemon while logged in
> as a user, it causes headaches.

OK.  When I tried it though, I was logged in as root.
 
> These are called xruns, that can be solved by properly tuning you
> system.

I have now tried 256 and it is quite good.  Had to set it using
qjackctl and did another reboot though, which is something I do not
like to do as it goes against all that Linux systems stands for eg.
being able to kill a process and restart it easily.

> Your distro, or system setup. I personally advise keeping things
> simple, and manually start jack when you want it started, with the
> exact settings you want to start it with.
 
> Yes this requres some JACK knowledge, but it is reliable, and
> consistent.

Absolutely.
 
> Hope that helps, -Harry

Thanks.  I'll take a look at he links you provided.  For now 256 seems
OK.
 
I will have to look into this a bit further since I have to compile
jackd from upstream.  The current one in this system prevents Ardour
from exporting audio.