Re: [fluid-dev] What is the best way start fluidsynth with zero/low latency?

[Joan Quintana]

Thanks Pedro,
I realise I made an ortographic mistake:

is audio.period-size=32, not audio.periods-size=32.

Now it works, and I found not necessary to put -o in the three parameters... 
But short form is better!

Joan Quintana


--- On Fri, 5/22/09, Pedro Lopez-Cabanillas <address@hidden> wrote:

> From: Pedro Lopez-Cabanillas <address@hidden>
> Subject: Re: [fluid-dev] What is the best way start fluidsynth with zero/low 
> latency?
> To: address@hidden
> Cc: "Joan Quintana" <address@hidden>
> Date: Friday, May 22, 2009, 10:16 AM
> On Thursday, May 21, 2009, Joan
> Quintana wrote:
> > if you avoid Jack and use alsa directly, I have my
> doubts in setting
> > latency (help is appreciated):
> >
> > $ fluidsynth -a alsa -m alsa_seq -l
> AI-APiano02trans.sf2
> >
> > > settings
> >
> > audio.periods            16
> > audio.period-size        64
> > synth.sample-rate        44100.000
> > -> 64 * 16 / 44100 = 23.2 ms
> > these are default values. But if I try my own
> settings, I find the same
> > settings.
> >
> > $ fluidsynth -m alsa_seq -a alsa -o
> synth.sample-rate=44100.000
> > audio.periods=2 audio.periods-size=32 -l
>  AI-APiano02trans.sf2
> >
> > > settings
> >
> > audio.periods            16
> > audio.period-size        64
> > synth.sample-rate        44100.000
> >
> > How can I tune and control real latency using -a
> alsa?
> 
> If you want to use directly the option names in the FS
> command line, you need 
> to  give -o for each one, for instance:
> 
> $ fluidsynth -a alsa -r 48000 -o audio.period-size=64 -o
> audio.periods=2 \
>              -o
> audio.alsa.device=hw:0 xxx.sf2
> 
> But it is exactly the same using this (much shorter)
> syntax:
> 
> $ fluidsynth -a alsa -r 48000 -z 64 -c 2 -o
> audio.alsa.device=hw:0 xxx.sf2
> 
> Note that the real hardware buffer size may also depend on
> the software layer. 
> If you access the device directly (-o
> audio.alsa.device=hw:0) the driver 
> tries to use the provided sizes, but if you use the layer
> "plughw:x" the real 
> buffers may be larger. In both cases ALSA may decide to use
> different values, 
> if the provided ones are outside the allowed boundaries.
> You can watch the 
> ALSA hardware parameters, looking a control file:
> 
> $ cat /proc/asound/card0/pcm0p/sub0/hw_params
> access: RW_INTERLEAVED
> format: S16_LE
> subformat: STD
> channels: 2
> rate: 48000 (48000/1)
> period_size: 64
> buffer_size: 128
> 
> The above command was executed after running FluidSynth
> with the following 
> command line:
> 
> $ fluidsynth -a alsa -r 48000 -c 2 -z 64 -o
> audio.alsa.device=hw:0,0 
> 
> Regards,
> Pedro
>