Bug#760758: amb-plugins: spurious LADSPA_PROPERTY_REALTIME

[Fons Adriaensen]

On Sun, Oct 19, 2014 at 11:50:05AM +0200, Frank Heckenbach wrote:
 
> As I said, it's a bit confusing, since two rather different
> properties include the word "realtime", and confusion about what the
> plugin itself may do vs. what the user of the plugin (the host) may
> do (and the use of the passive voice in the comments doesn't help to
> clear the confusion ...)

I've never had any problem understanding the difference between
the two, thank you.
 
> LADSPA_PROPERTY_REALTIME indicates that the plugin itself *has* a
> realtime dependency. That would be the case only for few plugins,
> not really audio processing plugins, more plugins for I/O.

We clearly disagree on the interpretation of PROPERY_REALTIME.

For all of my plugins the following is true: if their output
is cached, or subject to significant latency, they will not
produce the expected result. Hence this must not be done, 
and setting the property is required to restrict the host.

If a user expects to hear a note played on a MIDI keyboard
without delay, then this requires the entire processing 
chain to do the right thing, not just the part that is 
talking directly to the MIDI device. All plugins in such
a chain have the same real-time dependency. This is most
obvious  for plugins that implement a synthesiser module,
e.g. a VCF, but in fact valid for almost all. Exception
would be plugin that implements e.g. a VU-meter or spectrum
analyser - it doesn't matter much if the result is displayed
with some delay (as long as that remains reasonable).


Another interpretation, closer to yours, would be that if
the plugin has REALTIME_PROPERTY set it can not be used in
any form of batch (non-real-time) processing. But that is
not what the text in ladspa.h says.


Ciao,

-- 
FA

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