Re: [fluid-dev] Major degradation in sound quality & cpu usage going from Ubuntu 11.04 to 11.10

[David Henningsson]

On 11/27/2011 02:59 AM, Aere Greenway wrote:
> *UBUNTU 11.04*
>
>
>     Polyphony parameter value without under-runs: *26*
>
>     DSP Load while playing: Usually in 20% range, sometimes in 30%
>     range, max 38.9%
>
>
> *XUBUNTU 11.10*
>
>     Polyphony paramater value without under-runs: *3* (16, with only 3
>     tracks playing)
>
>     DSP Load while playing: In the 50% range, often getting up into the
>     60% range.
>
>     *Note: It will not play a single-track piano part without generating
>     under-runs.

Just for the record, this is extremely low. You should be able to get 
hundreds of voices, even with a 933 MHz machine.

You have configured memlock correctly, right? That is, when you start up 
fluidsynth, you should *not* get this warning:

fluidsynth: warning: Failed to pin the sample data to RAM; swapping is 
possible.

> On 11.04, all of these machines would perform the test piece on Qsynth
> without under-runs (though on the 933 megahertz machine, the Qsynth
> polyphony had to be set down to 26).
>
> I will do further testing with my 1.5 gigahertz machine, since this is
> one of the target machines I originally planned to use.

There was also a change between using single precision and double 
precision by default. I don't remember exactly between which versions, 
but I wonder if old machines like this one could be negatively affected 
(performance wise) by that change.

933 MHz, btw? Is that a Pentium III? Twelve years old or so? Pentium III 
generation had a significantly worse FPU than later processor 
generations (Pentium IV, AMD Athlons).

Unfortunately I don't have any old machines around to test with.

// David