On 05/09/14 14:08, Rui Nuno Capela wrote:
> 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.
>
I should probably drop out of this conversation as I haven't used
QTractor nor have I used any external gear for quite some time. But if
the issue is with external then you also need to bear in mind that you
might send some internally and some externally, so applying the same
delay to everything will still put some parts out of time with others. A
toggle for a MIDI channel going to int/ext could possibly be one solution??
Or if it is related to internal audio ssync I have to admit I am also
stumped why this would happen, as all audio coming out of the computer
would be going through the same audio buffers (Jack) and delayed the
same amount!
>> 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 :)
>
Plus (extrapolating from Ralf's comments) you clearly do already provide
a way for the adjustment to be done manually! Even if it is harder work
for the user...
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Received on Fri Sep 5 20:15:03 2014
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