Re: [fluid-dev] dsp_buf[] type

[David Henningsson]

Hi Brad,

If you're interested in different resampling algorithms, there was some 
work related to this in the PulseAudio community a while ago (performed 
by Alexander Patrakov).

He also made some images ( https://imgur.com/a/jtIEj ) - translated to 
fluidsynth's domain, I think "trivial" would be our "interp 0" and 
"src-linear" would be our "interp 1".

Also remember that these artifacts are of far less magnitude than the 
original waveform: If an oscilloscope has an accuracy of ~1%, I believe 
the artifacts will be lost in the inaccuracy of the oscilloscope.

See 
http://lists.freedesktop.org/archives/pulseaudio-discuss/2014-August/021362.html 
for more information about Alexander's research and what his images 
really mean.

// David

On 2016-01-04 00:23, Brad Stewart wrote:
> Regarding the previous post...
>
> It seems this is done in the function /fluid_rvoice_buffers_mix /in the
> file "fluid_rvoice.c."
> The output is buf[] and is also type fluid_real_t.
> So  I'm assuming the rendering engine can accept floating point values.
> I'm still trying to see how the linear interpolation is able to remove
> most of the low frequency artifacts.  none of the simulations and
> experiments don't result in the output I'm seeing from FluidSynth.
> Perhaps the audio h/w has additional filtering functions.
>
> Is there a way I can save an output wave to a file?  I want to look at
> the audio data before it's rendered.
>
> Thanks,
> Brad
>
>
>
>
> On 01/03/2016 01:27 PM, Brad Stewart wrote:
> > The interpolation routines place the processed data into dsp_buf[] of
> > type fluid_real_t.
> > I'm assuming you eventually convert this to int16 for rendering.
> > Can you point me to the section of the code that does the conversion?
> > Are you doing anything else, such as a moving-averaging filter?
> > Thanks,
> > Brad
>
>
>
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--
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic