[Ardour-Dev] Recording may channels at once

[Kjetil S. Matheussen]

On Fri, 4 Jul 2008, Sampo Savolainen wrote:

> On Thu, 2008-07-03 at 16:25 +0200, Kjetil S. Matheussen wrote:
> > (cc to ardour-dev)
> > 
> > 
> > On Wed, 2 Jul 2008, Thomas Vecchione wrote:
> > >
> > >
> > > And is far from a standard setup as well;)  If the OS is running from
> > > memory, and you are not swapping anything in or out of the swap partition(Or
> > > file as the case may be), but are still running X, GUI based programs(Azerus
> > > etc.) and doing 128 tracks of recording, all from a single disk, you are
> > > pretty lucky IMO, even on Linux.  I can't even depend on 64 tracks without a
> > > dropout due to disk access on a system disk.  32 is even pushing it, but i
> > > will say I have done it.  This is running Ardour, X, e17, jackd, and that is
> > > about it, on a properly patched kernel, with proper PAM permissions, but
> > > that does still have logging set up etc.
> > >
> > 
> > I think this might be because ardour records to separate files. I just
> > tried recording 128 channels in ardour using 16 X 8 channel tracks,
> > and it failed quite immediate. Recording 128 channels using jack_capture,
> > on the other hand, seems rock solid. Recording 64 channels (8 X 8) in 
> > ardour seems to work fine too.
> 
> Your CPU might be running out of time, or your disk system (platters or
> filesystem or memory).
> 
> > However, it could also be because Ardour does some graphical operations
> > while recording. Is there any way to turn off all that?
> 
> You can disable showing waveforms while recording (View->show waveforms
> while recording). You used to be able to disable the "pink boxes" also,
> but I can't find the option in 2.0 ongoing at the moment. But ...
> 


I just did some benchmarks recording 128 channels (16 X 8):

Recording times before failing, without waveforms while recording:
55s
19s
8s

Recording times before failing, with waveforms while recording:
16s
24s
18s

I run some other programs in the background accessing the
disk, so that could explain the large variations.


However, recording times before failing, using jack_capture,
128 channels, 5 second buffer, "$jack_capture -dm -B 5 -c 128" :

Manually stopped after 7.59 minutes, no failure.



> > Perhaps this is an area where Ardour could be optimized quite a bit?
> 
> .. If jack (and thus, the Ardour audio thread) is running with realtime
> scheduling plus you have a sane kernel and enough memory - none of these
> things really matter. The audio and disk threads will always get
> priority over the GUI and thus no pink box will interfere with the
> performance that really matters.
> 

Yes, but jack_capture only writes to one file, while ardour
writes to several. That could explain the difference.



> Oh, and proper scheduling also promises food for everyone and world
> peace.
> 
>  Sampo
> 
> 
>