13 Sep
2015
13 Sep
'15
5:07 a.m.
On Wed, 2015-09-09 at 22:56 +0200, IOhannes m zmölnig wrote:
hi richard, paul, stefan and fellow LADders,
the Debian folks currently are a bit at a loss of the proper
interpretation of the LADSPA_PROPERTY_REALTIME property.
ladspa.h says:
We changed the name of this to "isLive" in LV2 to avoid confusion with
the heavily overloaded term "realtime".
I believe #1 is the intent. The hint serves to distinguish plugins that
have some dependency on real time, from those that do not (only
processing their input). The latter can be used in a more functional
way, being called to process a block whenever, where the actual time run
is called is irrelevant. The hint being set essentially means "if the
plugin is activated, run() must be called regularly at a rate roughly
corresponding to the passage of real time"
Th comment says "plugin has a real-time dependency (e.g. listens to a
MIDI device)" which seems pretty clear. Explanation #2, while perhaps a
useful thing in some circumstances, really does not follow from the
hint's definition.
--
dr
/* Property LADSPA_PROPERTY_REALTIME indicates
that the plugin has a
real-time dependency (e.g. listens to a MIDI device) and so its
output must not be cached or subject to significant latency. */
the discussion started about a year ago (see [760758]), and it seems
that there are two opposing interpretations of that property:
#1 setting the property indicates to the host, that the plugin must not
be used in a non-realtime environment.
this means that a plugin that has this property set, must not be used
for batch processing, e.g. because it uses wall-clocked input (like
MIDI-devices) that simply won't deliver proper input when running at a
speed that is decoupled from wall clock.
OR
#2 setting the property indicates to the host, that the plugin can be
run at a lower (timing) priority; so the host can deliberately add
latency without compromising the usefulness of the full processing
chain. that would be mostly for plugins that do not do any input ->
output processing, but only take input (e.g. metering, recording).