Subject: Re: [linux-audio-dev] LADSPA and run_adding()
From: Roger Larsson (roger.larsson_AT_norran.net)
Date: Tue Nov 21 2000 - 00:44:41 EET
On Sunday 19 November 2000 12:49, David Olofson wrote:
> On Sat, 18 Nov 2000, Kai Vehmanen wrote:
> > On Fri, 17 Nov 2000, Paul Barton-Davis wrote:
> > > I have to laugh - here's the exact opposite point of view from
> > > vst-plugins today, about processReplacing, which is the equivalent of
> >
> > [...]
> >
> > > Can both points of view be right ?
> > >
> > :) Yup, been following the same vst-plugins thread. But seriously,
> >
> > this guy is just comparing run_adding() and run_replacing() using one
> > use case.
>
> Yep. And we actually have three situations to take into consideration
> here;
>
> 1) plugin taking data from one buffer, mixing into another
>
> 2) plugin taking data from one buffer, overwriting another
>
> 3) plugin taking data from a buffer, while overwriting it
>
>
> The third case is what breaks some of the reasoning behind switching
> to run_adding() as the default. run_adding() requires extra buffer +
> zero operation in chains (3), whereas run() requires extra buffer +
> add in mixers (1). run_adding() also requires an extra zero operation
> to overwrite a buffer (2).
>
With run_replacing you may do 3) in chains with only one buffer !
If the engine that allocs buffers know that a plugin is never looking
back - impossible with run_adding !!!
/RogerL
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