Subject: Re: [linux-audio-dev] midi events in jack callback (was: Reborn)
From: Juan Linietsky (coding_AT_reduz.com.ar)
Date: Fri Aug 16 2002 - 19:03:47 EEST
On Fri, 16 Aug 2002 09:40:01 -0400
Paul Davis <pbd_AT_op.net> wrote:
I sent a mail about this to the alsa-dev list, but didnt really get an
useful
answer.
I ran into the following problem when running my sequencer and my
sofsynth
together. Using ALSA sequencer, I can set a timestamp to the midi
event just fine,
in ticks, absolute value, etc. Alsa will take care of delivering "at
the right time".
This is not bad, but it's not enough when you are working with
relatively big
fragment sizes, alsa sequencer wont proovide any useful timing
information.
We know that the ideal way of doing this is having both the sequencer
and the
softsynth access to the same exact clock for reference, then having
the audio app
a predefined "delay in time" consisting of the fragment size. After
that it's
a simple matter of taking the current time before mixing a block, and
mix internally
in smaller blocks while retrieving the event.
I see this as something JACK could do really well (take the timing
before mixing a block
and give it to the processes, so even if one has to wait for the other
according to the
graph, the sync with midi would be fine. I guess basically this alone
may justify giving jack
midi superpowers, since we know how important a good midi sync is.
Juan Linietsky
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