Re: [alsa-devel] Re: [linux-audio-dev] Re: Toward a modularizationof audio component

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Subject: Re: [alsa-devel] Re: [linux-audio-dev] Re: Toward a modularizationof audio component
From: Abramo Bagnara (abramo_AT_alsa-project.org)
Date: Sat May 05 2001 - 19:31:51 EEST

Jim Peters wrote:
>
> Abramo Bagnara wrote:
> > I think there is some misunderstanding, the solution I proposed for
> > single thread audio engine is the following:
> >
> >
> > audio_producer1 ----\
> >
> > audio_producer2 -----\ /-- audio_consumer1
> > > engine <
> > audio_producer3 -----/ \-- audio_consumerN
> >
> > audio_producerN ----/
>
> I can't make sense of this, because for me the server engine is BIG,
> enclosing all the producers and consumers, which talk amongst
> themselves inside it:

Just think to my -----> as functional link (all the things I've drawn
are in the same process) using ALSA PCM API, and then you get what
you've drawn (if I assume that +---+
                               | |
                               +---+ is the process boundary).

>
> (GUI for a plugin) (ALSA pcm_shm interface to
> || || some other process)
> +--------------------------||------------------||----------------+
> | ENGINE, containing: (more plugins) |
> | | |
> | [HW input via ALSA] -> [plugin] -> [plugin] -> (whatever) |
> | | | |
> | [plugin] <- [plugin] -> [plugin] |
> | | |
> | (whatever) -> [HW output via ALSA] |
> | |
> +-----||------------------------||-------------------------------+
> || ||
> (GUI for a plugin) (GUI for a plugin)

But with some differences:

- you assume that plugin chain is something that engine need to know
statically, while I say that engine get audio from zero or more producer
and put audio to zero or more consumer independently from what is hidden
behing them.
- a related difference is that you put at extremity two hardware while I
say that's not necessarily true.

I try to redraw my example using your graphic conventions:

       GUI visual scope
+------||-----------||-------------------------------------+
| audio_producer1 ----\ |
| audio_producer2 -----\ /-- audio_consumer1 |
| > engine < |
| audio_producer3 -----/ \-- audio_consumerN |
| audio_producerN ----/ |
+-------||-----------------------------------||------------+
       appl file writer thread

Now, let's zoom on audio_producer1:

                  GUI visual scope
                   || ||
 ------------------||--------||-------
                   || ||
   HW capture -> plugin -> meter ->

Zoom on audio_producer2:

             GUI
             ||
 ------------||----
             ||
   file -> plugin ->

Zoom on audio_producer3:

    appl -> pcm_lbserver
      ||
 -----||--------------
      ||
   pcm_shm ->

Zoom on audio_consumer1:

  -> pcm_file_writer -> HW playback
           ||
-----------||-------------------------
           ||
    File writer thread

All is limited only by your fantasy and mips available ;-) 

-- 
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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