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Re: [fluid-dev] Major degradation in sound quality & cpu usage going fro

From: David Henningsson
Subject: Re: [fluid-dev] Major degradation in sound quality & cpu usage going from Ubuntu 11.04 to 11.10
Date: Sun, 27 Nov 2011 05:46:25 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1

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

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

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