off the top, if people are serious
about comming up with a good
architecture, someone should sit
down and codify all the implicit
specifications requirements that
are floating around. this sort of
thing should be done before the
API to make clear what the goals
are. discussions of "what if i
want to do _____" will become a
lot more clear.
i guess the obvious goal is
standardization so that everyone
can use each others plugins. my
first question is then, "what is
a plugin ?". more specifically....
there seems to be different ideas
about the processing granularity
plugins should support. on one side
is a view of plugins as little bits
of equipment you might have on the
rack in the studio. each with a set
of knobs and audio in and out.
another conception leans towards
plugins which are on the scale of
fundamental dsp operators, things
like FFT, derivative, convolution,
etc.
*** it appears to me this distinction
hinges on whether we want plugins to
generate controll signals which drive
other plugins ****
i think once this granularity question
is determined, a lot of other answers
will settle out for free.
______________________________________
for large grain:
metaphor is plugging together hardware
in the studio.
the questions about FFTs and cyclic graphs
are probably unimportant since that sort
of thing wouldn't ever be done.
specification of the controll signals
probably only needs to take place between
developers instead of the runtime level.
xml descriptions of controll signals are
only of interest once you get up inside
the gui layer. they are usefull for things
like pluggable looks a feels etc. the
connection between plugins and the gui
layer probably shouldn't be burdened with
this. a particular host might like xml
descriptions of the plugins it uses. since
the values don't really mean anything
outside the context of the plugin, there
is no reason they shouldn't be scaled 0-1.
one thing that seems to trouble people
is plugins which generate status signals.
my take on this is that the gui layer
would have to manage polling the plugin
in the same way that somewhere in the
xevent system, someone goes out and
polls/services the mouse. this may not
mesh nicely with GTK but i think the
level of abstraction for a plugin should
be the same as that for a mouse...sitting
somewhere down close to the hardware in
the realtime domain.
--------------------------------------------
for fine grain:
metaphor is some pictures from your
college dsp textbook
being able to use the output of one
plugin as the controll signal for another
becomes very important. maybe the
results of an FFT or tree-structured
filter bank are controll signals which
affect a synthesis bank ? things like
implementing reverb using circular
connections is necessary.
xml descriptions of controll signals are
not particularily usefull. would probably
rather have strongly typed data.
--------------------------------------------
my impression is that the large
granularity case is a lot more
interesting. lower level dsp
code is better shared as a function
library than kludged out of plugins.
if you want a modular synth or a
reverberation model, build it and
feed it's output into a network of
other plugins. i would want my
audio workstation to emulate an entire
studio rather than a particular
dsp algorithm.
someone is going to tell me that
they want to implement a system
which supports both granularities.
this strikes me as a mistake.
yes it's probably possible to make
a totally generic API which will
let you interconnect anything and
everything just like your old
modular synth. however, what host
is ever going to actually want to
support a true mixture ? aiming
for something totally generic is
a noble cause but such projects
collapse under their own weight
or never actually get used because
they have absurd learning curves
etc.
sorry this got so long. i'm new
to the list so slap me if i'm out
of line ..... my interests lie
towards a system with a GUI which
is actually a bunch of hardware
knob boxes i can use to control
a realtime, linux-based sound
engine in a live performance
situation.
regards,
charless
