Re: [linux-audio-dev] [ardour] custom graphics + MIDI control for LADSPA plugins

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Subject: Re: [linux-audio-dev] [ardour] custom graphics + MIDI control for LADSPA plugins
From: Paul Sladen (paul_AT_sladen.org)
Date: Fri Dec 01 2000 - 09:21:16 EET

On Fri, 1 Dec 2000, David Olofson wrote:

> On Thursday 30 November 2000 15:13, Steve Harris wrote:
> > On Thu, Nov 30, 2000 at 04:43:24AM +0100, David Olofson wrote:
>
> However, just dealing with the memory management isn't enough - truly
> hard RT instantiation capable plugins must also be able to do all
> init processing (create, init, prepare, start etc...) in about the
> same time as an average run()/process() call in the actual net. This
> might be a problem for plugins with large buffers or LUTs that are
> generated at init time, especially in very low latency settings. (A
> buffer could be 32 *bytes*...) This becomes very critical in systems
> that may occasionally instantiate lots of plugins during the same
> cycle.
>
> Now, one could "cheat" some, and accept that some plugins need one or
> more cycles to fully initialize, but that would require that the init
> code can be chopped up in arbitrary size bits. Possible but not
> beautiful...

For heavens sack, why(?) are you talking about doing initilisation in RT??

/*** non-RT: ***/

  plug->set(FOO, 42);
  plug->set(GAIN, 2.0); // can be set anytime
  plug->set(BLOCK_SIZE, 32); // is fundemental, requiring LUT regeneration
  plug->connect(IN, ibuffer);
  plug->connect(OUT, obuffer);

  plug->begin();
    /*** RT: ***/
    // on return, plugin expects to be in RT... don't do anything stupid!
    // (like malloc() ;-)

    plug->run();
    plug->run();
    plug->run();

    //GAIN is "non-complex", and can be set anytime.
    plug->set(GAIN, 1.5);
    plug->run();

    /*** non-RT: ***/
  plug->end();

  // changing the block size is a fundemental operation, for instance
  // it may required a LUT recalc, which may require a malloc(); etc
  plug->set(BLOCK_SIZE, 64);

  plug->begin(); // into RT
    plug->run();
    plug->run();
  plug->end(); // end RT

-*-

note however that begin(), and end() are different from the functions to
allocate a new instance of the plug. (which also would be done outside of
RT because it is likely to require calls to black-boxes like malloc.

  if(!(plug = groovy_foo_modulating_amp_new()))
    die("couldn't create new plugin instance);

    plug->init();
    plug->set(FOO, 42);
    plug->set(...);
    plug->connect(...);
    plug->begin();
      plug->run(); // (from RT thread)
      plug->run(); // (from RT thread)
    plug->end();
    plug->destory();
  groovy_foo_modulating_amp_delete(plug);

-*-

Paul 

--
e: paul_AT_sladen.org   t: 0115 922 7162

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