[LAD] Midi tempo sync'd live drum machine

[Ralf Mardorf]

On Thu, 2010-07-15 at 21:14 +0100, James Morris wrote:
> On 15 July 2010 20:27, Nathanael Anderson <wirelessdreamer at gmail.com> 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 at rncbc.org>
To: Ralf Mardorf <ralf.mardorf at alice-dsl.net>
Cc: Robin Gareus <robin at gareus.org>, Devin Anderson
<devin at charityfinders.com>, qtractor-devel
<qtractor-devel at lists.sourceforge.net>, 64studio-devel
<64studio-devel at lists.64studio.com>, Linux-Audio-Dev
<linux-audio-dev at lists.linuxaudio.org>
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