On 2014-09-05 02:32, Kazakore wrote:
On 05/09/14 03:56, Rui Nuno Capela wrote:
On 09/04/2014 10:34 PM, Ralf Mardorf wrote:
This year You record an audio track with an I+O latency of 10.7 ms.
Two year later you want to restore this session, but you don't
remember
the jackd settings you used. Originally audio and MIDI tracks were in
sync, when you used 10.7 ms I+O latency. Within the years you got new
hardware, you don't remember what latency you once used and starts
jackd
with a lower I+O latency. Nothing bad would happen for Ardour users,
but
a Qtractor user would run into sync issues. Am I mistaken?
i really don't get why it would have worse or better sync depending on
jackd latency settings. please forgive me, but i don't see it directly
related to the case of audio vs. midi sync...
though, in the special case that comes to mind, iif the alsa-midi
timer is slaved to a pcm sound-device, as against to the system or
hires timer for instance, you probably will get it different whether
running on disparate buffer-sizes, periods and/or sample-rates, that's
for granted--well, if you change the sample-rate across sessions you
will get prompted to convert into a brand new and different session
anyhow ;)
byee
Huh??
So you have audio coming from the PC and MIDI going out to external
sound generating MIDI devices and you don't see how output latency
from the computer can affect the timing sync between sound from the
computer and sound from the audio modules??? Surely even a blind
wombat could see that! Unless there is some magic in Jack/AlsaMIDI
which automagically delays the MIDI by the same as the output buffer
settings of Jack. Then some might also want to add a fixed delay value
to take into account the hardware delay (propagation time) but I think
we really are getting a bit complex now!
re. external midi equipment, probably yes, that might be pertinent,
but...
my point was about audio and midi sync within qtractor (the sequencer)
internally. once midi gets out of the sequencer or even of the machine,
then i doubt one can ever compensate effectively for the delay, drift or
jitter that will be always present, no mater how small but orthogonal to
jackd buffer-size, periods or sample-rate, whatever, and sure matters to
a perfect sync. i doubt the output latency of the in-machine jack-audio
graph might be any significant or functional to that goal.
Although I very much doubt anybody would be able to hear the
difference if you're only talking a couple of ms and have different
sounds both internally and externally (same sounds would cause comb
filtering and eventually echo once latency became high enough.)
exactly :)
But this is true for ALL audio coming out of the sequencer, whether
you recorded it or it's from a sample-pack or a soft-synth etc etc.
tl/dr: All that is really needed is an option to delay MIDI signals by
the amount of the audio output buffer (plus you could add the optional
hardware delay in settings if you really wished). This should bring
output of both audio and MIDI sounds as close to sync as is possible,
with the real-world systems being as imperfect as they are.
cheers
--
rncbc aka. Rui Nuno Capela
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