Re: +trigger, Re: [linux-audio-dev] ladspa.h.diff

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Subject: Re: +trigger, Re: [linux-audio-dev] ladspa.h.diff
From: Tom Szilagyi (st444_AT_hszk.bme.hu)
Date: Fri Mar 05 2004 - 20:14:41 EET


On Fri, 5 Mar 2004, Tim Goetze wrote:

> >the attached patch proves that LADSPA can be extended without breaking
> >binary compatibility. i've compiled plugins against a patched ladspa.h
> >and run them in hosts compiled against ladspa.h version 1.1 without
> >experiencing any problems.

Hi,

I like this new LADSPA spec. very much, thanks to Tim Goetze for working
it out! However, i have one bit of concern:

  /* This member indicates the delay, in 1 / (sample rate) time units,
     the plugin imposes upon processed signals. */
  const LADSPA_Data Latency;

Wouldn't this break the possibility of adequate operation of plugins that
have a latency value dependent on user settings (ie. not constant)?

Previously it was said that only a few plugins need this, and it's hard to
implement it in a host. I agree. But there *are* plugins (i have one) that
rely on the possibility of varying latency to keep the output synced, and
some (serious, sophisticated) hosts could still choose to implement the
varying compensation. If it is forced to have a constant value, these
plugins and hosts will have to face a compromise. If it is not specified
as constant (ie. it can be overridden by "latency" output, or some other
way on-the-fly) then the hosts that don't implement varying compensation
would work no worse than with this constant spec., but the possibility
to have "advanced" hosts and plugins that use it would still remain.

So, i would propose to leave this Latency specification in place (for the
95% of plugins/hosts that don't need anything more), but state that the
value written to the "latency" output (if that output is provided by the
plugin) overrides this value and that could be changed anytime. What do
you think? (This kind of usage of "latency" output has to be implemented
in hosts anyway, so it may not be needed to change anything in this LADSPA
spec -- maybe state in the comment that it can be overridden, that's all.)

Tom


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