Re: [LAU] -ck patch

On Mon, Dec 13, 2010 at 03:25:44PM +0100, Robin Gareus wrote:
> On 12/13/2010 02:28 PM, Raffaele Morelli wrote:
> > 2010/12/13 Robin Gareus <robin@email-addr-hidden>
> >
> >> On 12/13/2010 01:13 PM, Paul Davis wrote:
> >>> 2010/12/13 Raffaele Morelli <raffaele.morelli@email-addr-hidden>:
> >>>> Hi you all,
> >>>>
> >>>> what do you think about that? Have you got some personal experience?
> >>>> http://ck-hack.blogspot.com/2010/10/bfs-in-real-time.html
> >>
> >> yes. In short: Desktop performance: amazing, Desktop-audio-performance:
> >> good, pro-audio performance: deficient.
> >>
> >>> This quote:
> >>>
> >>> "If you were doing semi-professional audio recording you might, and
> >>> then you'd need to understand the inner workings of the software and
> >>> the -rt patchset to make the most of it. Just patching it in and
> >>> expecting it to work for you will not really give you any advantage."
> >>>
> >>> is not really true. It is true that there are quite a few complexities
> >>> to using the RT patchset's full capabilities. Most people probably do
> >>> not use them. But this doesn't mean that a general claim that the
> >>> patchset offers them no benefits is wrong.
> >>
> >
> > I really hoped that :)
> > I am now sure that RT patchset is something for kernel folks to deal with,
> > but neverthless that it's something good to apply for me.
> >
> >
> >
> >> quite, but it is true in the sense that it is much easier to screw up a
> >> kernel by blindly applying patches and generating a .config if you don't
> >> know what you're doing (and sometimes even if you know what you're
> >> doing). Also, one needs additional tools (like rtirq) to make good use
> >> of RT-linux, while -bfs runs OOTB.
> >> However these days most distributions do that setup for the users.
> >>
> >
> > well, I always followed
> > http://www.alsa-project.org/main/index.php/Low_latency_howto and never
> > screwed up a kernel
>
> Lucky you :) The information on the alsa-wiki is very good, but not
> every user is diligently following instructions as you do.
> It is also much easier to make a custom kernel that runs on one (your)
> system only, than tackling the task of compiling one that can be
> distributed.
>
> >> I don't care so much about speed. The important issue in pro-audio is
> >> reliability. It's not the smallest possible latency that counts, but the
> >> max. latency of the system.
> >>
> >
> > I really did not understand this statement and anyway I would not agree...
> > why anybody should be safe knowing that his box max latency is 20ms instead
> > of 50ms or 70ms?
>
> The max. system-latency determines the audio-latency at which you will
> never have any x-runs. (The minimal and avg. latency determines the
> speed and reactivity of your Desktop.)
>
> Without the RT-linux patch you may be good at 99.9% of the time, but
> since there is no guarantee for system-latency: there may be drop-outs.
>
> And Murphy says that this 0.1% chance will always become real when
> you're on stage in the middle of a performance. The resulting click will
> not only kill the PA but half the audience will sue you for becoming
> deaf ;-)
>

I don't get clicks, but with my latest bass setup (using LinuxSampler instead of FluidSynth), I occasionally get moments where all audio just stops for a second or two, then whatever notes have been played suddenly rush out in a thundering-herd kind of situation. I suspect this may be a LinuxSampler issue since I've heard it happen before with other gigs, and it may possibly be related to slow seek times on my SSD on my EEE.

I've also in the past had fluidsynth cause nasty stuttering (like a DJ snare-rush kind of sound), particularly with a grand piano soundfont when I get kind of violent with it, hammering a chord or interval repeatedly Jerry-Lee-Lewis-style with varying velocities.

I'm going to be using this new setup (using LinuxSampler for bass instead of FluidSynth) for the first time live on the 29th, it will be interesting to see how it goes.

-ken
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Received on Tue Dec 14 00:15:02 2010