[fluid-dev] Re: What is the best way start fluidsynth with zero/low latency?

[jimmy]

> Date: Thu, 21 May 2009 15:19:26 -0500
> From: "S. Christian Collins" <address@hidden>
>
> Regarding the rt kernel, it seems that the newer default
> Linux kernels 
> seem to handle realtime audio quite well even without using
> a rt 
> kernel.  I stopped using the rt kernel in Kubuntu
> 9.04, because the 
> standard kernel seems to perform just as well, but without
> the 
> instability the rt kernel brings.  Does anybody else
> have a similar 
> experience?
> 
> -~Chris
> 


Re: What is the best way start fluidsynth with zero/low latency?

The fastest way and shortest answer is to install Linux from a music (MIDI) 
oriented liveCD.  Read below for more info.


---

The last 5-6 Linux kernel releases had high-resolution timer features that will 
work with for MIDI low latency.  The last 2-3 kernel releases had merged in the 
realtime patch.  But recently there is a new kernel realtime patch started 
again by the same people.  Started a while back when I compiled my own kernel, 
I only needed the high-resolution timer configuration, I don't use the realtime 
kernel patch, and high-resolution timer works fine for MIDI low latency.

If I am not mistaken, using Alsa directly normally only alow one app to use the 
sound card at any time.  Using Jack, it works as a virtual mixer of sort for 
all jack-enabled apps.

Midi low latency involves configurations of various hardware, linux kernel, and 
softwares that are specific to real-time response for midi events.  It can be 
overwhelming for new users.  I highly recommend starting with a music/MIDI 
oriented Linux liveCD distro.  LiveCD allows people to just boot directly from 
the CD/DVD and it takes care of auto configuration.  These music oriented 
liveCD already has either realtime or high resolution timer kernel 
preconfigured and will launch jackd preconfigured in their application menu.

If pianobooster.sourceforge.net is somewhat stable (usable) and don't have 
licencing problems, you may want to lobby the various music oriented liveCD 
distro to include PianoBooster on their CD.  Some of those liveCD's I can 
remember right now are Musix, PureDyne, 64 Studio.  Although, the latest Musix 
beta is now half of a DVD so it should have plenty of room.

These 3 liveCD are Debian compatible (can use Debian repositories directly) and 
can be installed onto hard drive if the users want to install more apps, or 
tweaks.  I haven't tried their recent releases, but some liveCD's running 
directly from the CD/DVD may allow for saving your configurations on to USB, or 
hard drive and use such configuration in subsequence boot from CD/DVD.  By the 
way, Ubuntu is Debian derrived (not directly compatible) and uses its own 
repositories.

------


This fluidsynth web page currently (2009-05) has some info for using Alsa 
driver directly.

   http://fluidsynth.resonance.org/trac/wiki/LowLatency



These links have info on kernel configuration, IRQ interrupt priorities, and 
jackd info.

http://sarigama.namaste.jp/micro/la.txt

http://www.rosegardenmusic.com/wiki/low-latency_kernels

http://code.goto10.org/projects/puredyne/wiki/KernelAndSystemOptimization

https://help.ubuntu.com/community/HowToJACKConfiguration

https://help.ubuntu.com/community/HowToQjackCtlConnections


Jimmy