30 Oct
2003
30 Oct
'03
10:10 p.m.
Now, for the case of a sofstsynth this scenario
doesn't fit, because the
synth is not zero latency. This means that a "tight" midi track is
audible with the softsynths output latency.
most softsynths are zero latency. only those that work in the
frequency domain tend to have non-zero latency. by this i mean that
the synth will generate output for a given time period at the same
time as processing any input it receives (which may be nothing at all)
for the same time period.
Now, Jack is really an audio server but it could also
be used to
communicate the latency of the softsynth to the Audio/Midi Sequencer. I
know there's calls to get the output latency of physical output ports.
But it would be nice to have calls to ask for the physical output
latency of clients [this value can be different for different clients -
maybe with different output devices].
the jack API supports this for every port of every client. its nothing
to do with particular classes of ports. it *is* up to the client to
set the port latency correctly.
This way, the audio/midi-sequencer could ask jack for a
list of clients
and offer this choice to the user who then can select which midi tracks
correspond to which softsynth. The Sequencer could then send the midi
events a tad bit earlier [the output latency of the softsynth].
ardour does exactly this. it delays all tracks by various amounts so
that they sync up with the most latent/delayed one. this includes
internal delays caused by plugins, and external delays due to signal
routing.
What do you think? I have no insight into the
implementation details of
jack, so i don't know how possible this scenario is and if it fits with
design decisions.
its already done :)
--p