Re: [fluid-dev] Multi-kernel system test

[Bernd Casper]

Hi David,

 

many thanks for the recommendations.

 

I've tested the most various combinations for buffers/buffer size/polyphony/kernels, also 2/1024/1024/1 and 2/1024/1024/2, and those setting increased the latency to a kind of "echo". In a real-time scenario, I cannot use a buffer size bigger than 512 (in respect to my average system).

 

>It is not intended to use more than one instance of FS. This means more
than one reverb engine, which in turn would consume more CPU in total.<

 

reverb:

I don't use the FS reverb engine at all, in my personal setup.

 

number of instances:

I already expected you to mention the number of instances. I experienced absolutely no slowdown of my system when using up to 20 instances of FS. There wasn't any noticeable change in FS reaction, when using just one single instance.

 

I'd enjoy to use one single instance of FS only. For several reasons this isn't possible presently.

- Technical reasons:

One important reason is that I separate the divisions of my instrument to output into different soundcards.

- Sound quality reasons:

I continue to use more than one instances of FS, since usage of only one instance of FS (and increase polyphony 8 times instead, to compensate) delivers no identical sound result - even if I know it should, theoretically. The stereo horizon is not the same, as well as the transparency of sound (in admiration for the great improvement the sound has taken with FS 1.1.2). If the number of samples increases over a certain point (no influence, how high I set the polyphony number), the "widescreen stereo" sound seems to change to a kind of "joint stereo" sound, what I want to avoid in any case.

 

Regards

Bernd.

----- Folgende Nachricht wurde empfangen -----

Absender: David Henningsson

Empfänger: bca

Zeit: 2010-10-01, 09:25:27

Betreff: Re: [fluid-dev] Multi-kernel system test

On 2010-09-30 13:23, Bernd Casper wrote:
> Hi David,
> this is quite interesting.

It is.

> In a real-time scenario using two kernels *slows down* latency and
> overall performance here, when using many programs simultaneously, while
> seemingly increases polyphony performance at te same moment (personal
> impression of my ears - stereo horizon is enlarged). I use
> buffers/size/polyphony 6/384/1024, and 8 instances of FS.
> Is this what's intended?

It is not intended to use more than one instance of FS. This means more
than one reverb engine, which in turn would consume more CPU in total.

So in theory, for best performance, I would recommend you to

1) use only one instance of FS (and increase polyphony 8 times instead,
to compensate)

2) use 2 buffers only - and increase size to 1024 to compensate. You
then might be able to decrease size to "trim" your system for better
latency.

3) experiment to see if increasing the "kernels" parameter, gives better
or worse performance. Extending it beyond the number of physical CPU
cores should give worse performance.

So if this gives the best performance in practice is more than I know -
  I'm not a computer scheduling expert, especially not on Windows.

(Btw, a few weeks ago I tried to set up jOrgan on Ubuntu Maverick here,
but I never got any sound output. I had to use jdk though, since
sun-java wasn't available for Maverick. Perhaps you or Sven could help
me out some day.)

// David