Re: [fluid-dev] DSP testing

[Peter Hanappe]

Josh Green wrote:
> Its really great to hear that you are running some synthesis validation
> tests. Whats your current setup for testing this? Are you using Jack? 

I use a dry recording of some piano notes. The recording is 6 seconds
long. I made a soundfont with this recording and them play a 6 seconds
long note. So the tests are still very "static", only testing the DSP
algorithm. I don't use Jack, I use the 'file' audio driver to record
the output to a file. Since I'm only playing 1 note, timing isn't much
of a problem. I compare the recorded soundfile with the soundfile
produced by the synthesizer.

> I have a feeling there are probably some issues with stereo output in
> regards to the phase offset between right/left speakers. Is there
> currently a way to guarantee multiple voices to all start at the same
> time? Playing the same note can often sound different for each note on.

No, there currently is any way to guarantee they start together. It
could happen that the audio thread intervenes between the initialization
of the first voice and the initialization of the second voice, in which
case the two voices are shifted by 64 samples. I should test whether
this really happens and think of a way to fix it if it does. Good point.

What suprises me is that it makes that big a difference that you hear
it. Is there any way you could record it?


> I've noticed that the damping parameter has no effect (at least as far
> as I can hear). Perhaps its just really subtle in its effect?

Did you try the version in CVS? I find that the reverb has improved
and the effects seem more intuitive now.

> On another note.. I was noticing that the filter turnoff optimization
> that I was messing with before is still not optimal. One can often still
> hear clicks or other audible changes when the filter transitions between
> off and on or visa versa. Perhaps once the filter gets turned on for a
> voice, it should remain on.

OK.

> Is the TODO file up to date? I'd like to see about helping with some of
> the items on that list.

I cleaned up the TODO file a bit. Don't add too much stuff to it. It's
demotivating to not see the list shrink.

>         Cheers,
>         Josh Green

Cheers,
Peter