Re: Re: [Denemo-devel] Portaudio

[Richard Shann]

On Fri, 2009-02-13 at 23:06 +0100, address@hidden wrote:
> > > Nearly right. You don't tell Jack anything about bitrate and
> samples. This is
> > all done by the Jack-Server.
> > Then that doesn't work, we have samples to output. (They are called I
> > think pcm samples, they are literally numbers representing the
> amplitude
> > of the sound wave at a succession of points in time). So what does
> Jack
> > want as input? What would Denemo have to give it? Jack-Midi can be
> given
> > MIDI codes, that's fine, but what does Jack want?
> > Richard
> >
> 
> I guess we misunderstood. Of course you can generate sounds with certain
> frequencies and send them to Jack. Maybe portaudio provides this feature
> out of the box?  You have to rewrite it or use some small lib for it. I
> think there are tons of applications which can generate sounds in any
> shape.
> 
> Jack just gets a stream of sound.. I think. 
!!! sound is compression waves in a material medium.
Jack does not want that. Microphones want that. They generate voltage
variations which are then turned into bit patterns in memory
(representing numbers) by the analog to digital convertors in the
soundcard.

So what does Jack need as input?
There is obviously a gap in our knowledge here. My guess is that Jack
would be something capable of doing bitrate conversion, sample format
conversion (e.g. uint16 to double, char to float ...), re-directing the
streams of data. *But* I guess that what you have to shovel in to Jack
is (ultimately) numbers representing the amplitude of the sound (i.e.
the offset of a loudspeaker cone from its rest position).
But that guess is just based on the fact that I can't imagine what else
it could want.

Richard