Re: [Qtractor-devel] [Fwd: Re: ; ) Was - Re: [LAU] Session management with NSM]

[Rui N. C. <rn...@rn...>]

On 09/04/2014 09:33 PM, Ralf Mardorf wrote:
> -------- Forwarded Message --------From: Ralf Mardorf
> <ral...@ro...>
> To: qtr...@li...
> Subject: Re: [Qtractor-devel] ; ) Was - Re: [LAU] Session management
> with NSM
> Date: Thu, 04 Sep 2014 22:31:15 +0200
> Mailer: Evolution 3.12.5
>
> On Thu, 2014-09-04 at 21:27 +0100, Rui Nuno Capela wrote:
>> On 09/04/2014 07:49 PM, Ralf Mardorf wrote:
>>> Rui :)
>>>
>>> please consider to automatically add to
>>>
>>> File > Properties ... > Description
>>>
>>> the jackd "in" and "out" reported latency ;). Since the MIDI resolution
>>> steps don't provide ms, frame information, a written note could help to
>>> fix sync problems, without using a calculator.
>>>
>>> (I don't need it, perhaps you could add an option to the preferences, to
>>> uncheck this feature ;)
>>>
>>
>> jack_lsp -l  does report latency of every port
>>
>> byee
>
> It doesn't report the latency a session was recoded 2 years ago.
>

and why would that be interesting?

qtractor does its "recording/input latency compensation" of audio cľips 
*at the time* the audio material is captured, so that material gets 
aligned with the audio/MIDI content already in session and possibly 
being played back at the time of the recording. never again it gets 
adjusted no matter what jackd parameters change later, be that for worse 
or better. that's it.

please understand that this is the only kind of latency compensation 
qtractor does and nothing else. nb. qtractor does NOT compensate for 
in-line output or plugin chain latency. never did and quite frankly it 
won't do so soon, i'm afraid.

i really don't see how having distinct jackd i/o latency settings 
(buffer-size, periods, sample-rate) may lead to audio going out of sync 
to MIDI--if it does get out-of-sync anyway, it is probably because 
something else but latency compensation related, not to tell that 
session-management has nothing to do with either.

cheers
-- 
rncbc aka Rui Nuno Capela
rn...@rn...

ps. if audio and MIDI get out of sync, timer type and/or resolution 
might be the top suspect.