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Re: [fluid-dev] ALSA driver consuming too much CPU

From: Paul Millar
Subject: Re: [fluid-dev] ALSA driver consuming too much CPU
Date: Thu, 16 Nov 2006 22:02:45 +0000
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Josh, Garett,

Thank guys for the quick reply.

Yes, the work-around worked fine:  when setting "audio.alsa.device" to "hw:0" 
I see the CPU usage drops to far more modest values.  
Setting "audio.alsa.device" to "default" (fluidsynth's default value, I 
believe) recreates the problem.  [as an aside, for me, this has nothing to do 
with running as root.]

I now set "hw:0" as a default (within monami), but allowed users to override 
it with an "alsadevice" monami option.  This should be fine, just needs 

So, in terms of documentation, would you say this is more of a problem with 
alsa than fluidsynth?  If so, do you know if it's fixed with a particular 
release of asla/libasound?

Finally, are there options that further reduce CPU usage, perhaps at the cost 
of loosing some sound fidelity?  I'd guess setting the audio output to 8-bit 
mono, dropping the sample frequency would take less CPU, but I can't seem to 
get the alsa driver to accept any of these options. [*]



[*]  I'm getting some weird errors and warnings when trying to set these.  The 
docs say audio.periods is limited to 2--64, but alsa (for me, at least) seems 
to have 65 as a lower limit.  I can't seem to set either audio.period-size 
nor audio.periods to explicit values: fluid_settings_setstr() always seems to 
fail.  For example:

fluidsynth> unable to set bufsize (audio.period-size) = 1000
fluidsynth> unable to set bufcount (audio.periods) = 65
fluidsynth> The sample rate is set to 44100, the synthesizer may be out of 
fluidsynth> Requested a period size of 64, got 65 instead
fluidsynth> ALSA driver: Using format s16, rw, interleaved

The "sample rate is set to 44100" warning is weird.  Although it doesn't say 
it above, I'm asking for 44.1kHz sample rate, so it shouldn't really be 
warning me here ... or am I missing something?

On Thursday 16 November 2006 20:57, Josh Green wrote:
> It is indeed known about, but should have been fixed a while ago..  I'll
> do my best to fix this issue and get a release out soon.  Best regards,
>       Josh
> On Thu, 2006-11-16 at 11:50 -0700, Garett Shulman wrote:
> > I believe that this is a known glitch between fluidsynth and alsa plug.
> > Check out:
> > http://www.mail-archive.com/address@hidden/msg00183.html
> >
> > Paul Millar wrote:
> > > The main reason for writing is I've noticed a problem with the ALSA
> > > driver.

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