Re: [linux-audio-dev] a central problem with *any* Port model?

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Subject: Re: [linux-audio-dev] a central problem with *any* Port model?
From: Abramo Bagnara (abramo_AT_alsa-project.org)
Date: Thu May 24 2001 - 23:50:35 EEST

Tom Pincince wrote:
>
> > > But wait a minute! Oh my, this is much worse than I thought. Much
> > > worse. There isn't *any* way to monitor the input of a Port in
> > > general! If it happens to be a port on a Driver that is controlling an
> > > audio h/w interface, then its possible. But in the general case, the
> > > notion of monitoring a Port is nonsensical - there is no mechanism to
> > > do it.
> > >
> > > Gulp. This seems bad.
> > >
> > > How can anyone build a disk recorder that cannot monitor its input
> > > effectively?
> >
> >
> > I've not understood what's the problem...
> >
> >
> > I see you've problems if you limit port data type to float ;-).
> >
> >
> > Someone can explain which other problems exists?
>
> Monitoring means sending a signal to an audio interface output. In the
> current model signals go from output ports to input ports, so the only
> signals that can access the input port of an audio interface output come
> from plugin output ports. There is currently no defined way of sending
> the contents of an input port to another input port, so there is no way
> to monitor the signal that is feeding a plugin.

Some ascii art:

     +-----+ +-------------+
     | HD | | CAPTURE PCM |
     +-===-+ +-----===-----+
        | |
        | +----------+
        |/
   +---===---+
   | `-------------+
   | PLUGIN | |
   +---===---+ +-----===------+
        | | PLAYBACK PCM |
     +-===-+ +--------------+
     | HD |
     +-----+

=== are ports

+--+
| | are soundboxes
+--+

------ are flows

With the model I've proposed this is natural: we have ports (where
buffers live) and we have flows from/to ports (one ports, many flows).

Note that PLAYBACK PCM is not *inside* PLUGIN, it's a read flow of its
input port. 

-- 
Abramo Bagnara                       mailto:abramo_AT_alsa-project.org

Opera Unica                          Phone: +39.546.656023
Via Emilia Interna, 140
48014 Castel Bolognese (RA) - Italy

ALSA project               http://www.alsa-project.org
It sounds good!

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