On 11/20/2012 01:58 AM, Jan Newmarch wrote:
> I ran perf (from linux-tools Debian pkg) on the RPi for nightsin.kar using 
> two soundfonts and got
>
>     32.07%   fluid_rvoice_buffers_mix
>     26.89%   fluid_rvoice_dsp_interpolate_4th_order
>     12.99%   fluid_iir_filter_apply
>     11.00%   fluid_revmodel_processmi
>
> for the FluidR3_Gm  and
>
>     29.49%   fluid_rvoice_buffers_mix
>     23.71%   fluid_rvoice_dsp_interpolate_4th_order
>     14.89%   fluid_revmodel_processmix
>     12.53%   fluid_iir_filter_apply
> ...
A lot of CPU is being consumed by the 4th order interpolation. Try
changing the interpolation to see if that reduces the CPU usage (it
should). To change to linear interpolation, you would use this command
in fluidsynth:

interp 1

Here are the possible interpolation values, to my knowledge:

*0 - No interpolation*: lowest CPU usage, but samples will contain
high-frequency aliasing (a "grainy" sound) when pitch-shifted.
*1 - Linear interpolation*: low CPU usage, but some aliasing is still
audible, especially with low-bitrate samples
*2 - 4th order (cubic) interpolation*: higher CPU usage, but no aliasing
is present when pitch-shifting samples. This gives a very professional
sound, and is the default interpolation method used by FluidSynth.
*3 - 7th order interpolation*: highest CPU usage and best possible sound
quality.

-~Chris
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