[LAD] Has anyone ever played a plugin in realtime ... [related to:] hard realtime performance synth

Benno Senoner benno.senoner at googlemail.com
Sat Feb 6 03:35:54 UTC 2010

Hi Emanuel,  regarding LinuxSampler the reliability and performance it
can achieve (polyphony, dropout-free playback etc)
depends from several factors:
hardware: mainboard, cpu, RAM, harddisk, audio card, gfx card
software: linux kernel (real time extensions), other running drivers, apps

as others already said some hardware like laptops are often not
optimally suited for glitchfree sub 10msec latency playback.
sometimes shared IRQs and other hardware bottlenecks can increase the
likelyhood of audio dropouts.

LinuxSampler is highly configurable, you can tune almost any parameter
including the polyphony, how much of each sample
is preloaded into RAM (reduces disk I/O), the number of disk I/O threads etc.

disk streaming audio samplers have to cope with the limited access
times and bandwidth of harddisks, so of course it cannot
 do a miracle and defy laws of physics. if the disk is physically
capable to stream only 50 voices and you try to play pieces with
100 active voices, it could go well for a while since when playing
short notes the initial part is cached in RAM but 100 sustained
notes will lead to drop outs or muted voices sooner or later.
You can easily fix the issue by either preloading more of each sample
into RAM, given enough RAM you can even avoid any disk I/O
at all and in that case the polyphony is limited only by the CPU and
RAM speed. = several hundred voices with sub 5-10msec latency.
 (Alex Stone had a LinuxSampler setup with 800 voices with disk
streaming actie).
alternatively you can stream the samples from 2 separate disks (best
solution is to place your instruments on multiple disks) or use
software RAID0/1 to increase disk bandwidth.
solid state disks are reported to work very well with harddisk based
samples since they provide low access times (often below 1msec) and
very high read speeds 100-200MB/sec.

If you need help with LinuxSampler just ask on our forum, users will
gladly and share their experiences with good performing LinuxSamplers

As said given non broken PC hardware, the a properly tuned linux
kernel with real time support and the right linux audio app you can
easily have a software instrument playable live
without audio dropouts and without notable latency. (  < 5-10msec)
given that it takes about 1.1msec to delived a Note On/Off MIDI
message and that sound travels 1 meter in 3msec,
playing a 4 note chord and standing 1 meter from the speaker leads to
7 msec latency (for the 4th note of the chord) even if your software
instrument had  0msec latency there is always some
latency present. so IMHO anything below 3-10msec is a real time instrument.


2010/2/4 Emanuel Rumpf <xbran at web.de>:
> 2010/2/4 Arnold Krille <arnold at arnoldarts.de>:
>> On Thursday 04 February 2010 18:50:28 Emanuel Rumpf wrote:
>>> Has anyone ever played a plugin in realtime ( live )...
>>> ...and I don't mean a one-finger melody, but a mutli-polyphonic piano
>>>  piece, eventually with sustain held down, which resulted in about 20 to 40
>>>  simultaneusly processed voices.
>> Yes, I have. I believe Ken Restivo, Atte Andre Jensen and many others too.
> Reliably ? At a latency below 10 ms ?
> Which synth ? I don't intend to mistrust you, but I remain
> disbelieving for now. :-)
> Linuxsampler is well written and reliable, but
> when playing intensely, it xran too here.
>>> We have dedicated hardware for graphics, why not for audio ?
>> There are manufacturers selling dedicated PCI-cards to do VST-plugin work and
>> free your cpu of that.
> Interesting, although uneligible for my laptop..
>> But whats the purpose of running some piece of (almost)
>> generic software on generic platforms, when you still need specialised
>> hardware?
> Being generic means (for the platform) to support a bunch of
> specialised applications.
> It doesn't bother much to buy additional hardware, in order to make
> the system more generic, but not being able to make it
> generic enough for being able to use it for a cerain specialised application.
> We are used to extend the systems usability through additional peripherials
> such as graphic-cards, audio-cards, printers....
> That's what has made it a success.
>> Of course you can buy dedicated audio-hardware. Its called keyboards and
>> synths and mixers and effects (outboard).
> These make me lose the generality.
>> But isn't it easier to have it all in software and carry it around on your
>> pc/laptop/usb-stick?
> It absolutely would, if it gave me the same reliability.
>> Please give us some pointers to help you improve performance on your definitely
>> un-tuned and probably mis-configured system before making our work bad in
>> general.
> I'm not making it bad. I'm even searching for a way to
> make it more valueable by making it more usable.
> I don't think my system is so badly configured - how to measure ?
> It's not the most recent hardware, I admit.
>> Have fun,
> Thanks
> --
> E.R.
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