Re: [LAD] Midi tempo sync'd live drum machine

From: Ralf Mardorf <ralf.mardorf@email-addr-hidden-dsl.net>
Date: Thu Jul 15 2010 - 23:26:21 EEST

On Thu, 2010-07-15 at 21:14 +0100, James Morris wrote:
> On 15 July 2010 20:27, Nathanael Anderson <wirelessdreamer@email-addr-hidden> wrote:
>
> > If I don't find anything I want to hack something together, so a primer on
> > midi tempo sync, and how to program with it would be appreciated.
>
> Hi Nathanael,
>
> I'm using JACK MIDI which makes it quite easy (compared with designing
> the program architecture) to output MIDI events.
>
> I'm also trying to use JACK transport to a) sync with other timebase
> master programs, b) to act as a simple timebase master.
>
> The JACK timebase and transport documentation focuses on using JACK to
> accomplish these tasks.
> see here: http://jackaudio.org/files/docs/html/transport-design.html
> There is also a transport example in the examples directory within the
> source code for JACK.
>
> But these documents do not go into the issues you'll come across when
> trying to accurately synchronize your application with another. Or
> accurately acting as timebase master (ie you've recorded some audio
> sequenced by your MIDI program acting as timebase master but it does
> not line up when imported into a DAW with the same tempo/meter).
>
> Beyond this, you'll have to look into other software source code
> (AFAIK). But it's far from trivial.
>
> Cheers,
> James.

Perhaps the source code for Qtractor could help.

I've got timing issues, but they have nothing to do with JACK transport.
I guess (didn't use it) JACK transport is okay, with the limits Rui
mentioned today. Usually Rui does good programming.

-------- Forwarded Message --------
From: Rui Nuno Capela <rncbc@email-addr-hidden>
To: Ralf Mardorf <ralf.mardorf@email-addr-hidden-dsl.net>
Cc: Robin Gareus <robin@email-addr-hidden>, Devin Anderson
<devin@email-addr-hidden>, qtractor-devel
<qtractor-devel@email-addr-hidden>, 64studio-devel
<64studio-devel@email-addr-hidden>, Linux-Audio-Dev
<linux-audio-dev@email-addr-hidden>
Subject: Re: [LAD] Transport issue for Qtractor - has impact to the
jitter issue
Date: Thu, 15 Jul 2010 09:33:53 +0100

On Thu, 15 Jul 2010 10:15:53 +0200, Ralf Mardorf wrote:
> Transport issue for Qtractor - has impact to the jitter issue
>

what transport issue? oh i see... :)

qtractor has in fact a known trouble with jack transport sync when slaving
to period/buffer sizes greater than 2048 frames. it skids. maybe that's
exactly what you're experiencing when running jackd -p4096.

i'll recommend for you to turn jack transport mode to "none" or "master"
only, never "slave" nor "full" on those situations (in
view/options.../audio/jack Transport).

another recommendation would be to grab the latest from svn trunk where
the said trouble has been already mitigated :)

cheers

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Received on Fri Jul 16 20:15:32 2010

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