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

[jonetsu at teksavvy.com]

On Sun, 14 Feb 2016 18:19:49 +0100
Ralf Mardorf <ralf.mardorf at alice-dsl.net> wrote:

> Then follow Len's advices:
 
> On Sat, 13 Feb 2016 17:04:45 -0800 (PST), Len Ovens wrote:
> >mv /etc/security/limits.d/audio.conf.disabled /etc/security/limits.d/audio.conf
 
> The defaults of Ubuntu might differ to the settings recommended here:
 
> "@realtime   -  rtprio     99
> @realtime   -  memlock    unlimited" -
> http://www.jackaudio.org/faq/linux_rt_config.html
 
> Consider to edit the values to the above defaults, resp. to
 
>   @audio 	- rtprio 	99
>   @audio 	- memlock 	unlimited

This is fine since it is set at 95.  memlock is also unlimited.

>   id
 
> if there's no group (audio) shown, you need to add the user to this
> group.

This is also OK.
 
> >install rtirq.
> >
> >As you are running a delta1010 (I think), sudo
> >edit /etc/default/rtirq... the line that says:
> >RTIRQ_NAME_LIST="something something"
> >to:
> >RTIRQ_NAME_LIST="snd_ice1712"
> 
> Reboot and after rebooting run

Now this might be the crucial point.  rtirq is installed and the rtirq
was modified to exclude anything but the sound card 

RTIRQ_NAME_LIST="snd_ice1712"

And then ./rtirq start was executed, as indicated in an advice here
and/or web page (sorry too many info at one time - can't complain
though ! :) and that is the important point.

By running 'rtirq start' the impression was given that there's no need
to reboot.  Which gave:

% ./rtirq status

  PID CLS RTPRIO  NI PRI %CPU STAT COMMAND
   87 FF      90   - 130  0.0 S    irq/8-rtc0
  547 FF      90   - 130  1.2 S    irq/18-snd_ice1

After a reboot it is:

./rtirq status

  PID CLS RTPRIO  NI PRI %CPU STAT COMMAND
  449 FF      90   - 130  0.7 S    irq/18-snd_ice1
   47 FF      50   -  90  0.0 S    irq/9-acpi

The other thing that was done is to set all scaling_governors to
'performance'.  Not so sure if this changed anything and I haven't
tested it yet.  I have asked before about the scaling_governor since it
is always mentioned during an Ardour install and I was left under the
impression that I should not care about this.

So.  After a reboot, the ardour session plays OK.  There can be
a faint, very sparse crackling noise although no

'JackAudioDriver::ProcessGraphAsyncMaster: Process error'

reported by jackd in the console jackd was launched, with both the '-p
128 and --sync' options.

It is now quite good.  I tried the setup with a few acoustic guitar
lines and it is no longer a fight to record something !  As is, it si
impressive.  There may very well be some fine tunings to do.  I would
also like to clean up the notes I have taken and post a summary of the
steps and a big thank you to everyone who helped !  

Cheers.