[LAU] [JACK] Can tempo be synced between hosts?

[Lorenzo Sutton]

Hi Francesco,

On 20/02/2021 12:08, Francesco Napoleoni wrote:
[...]
> 
> However I cannot find a way to transmit tempo changes from master machine to
> slaves.
> 
> I’ll try to explain myself better: the “master machine” is a PC with a
> soundcard, running JACK on a Linux Fedora OS, and is connected with the
> “slaves” with a gigabit ethernet link. The “slaves” are currently two, but I
> would like to expand this to a wider configuration, maybe with devices such as
> Raspberry sharing the load of multiple synths, effects and so on.
> 
> The problem is that I can see the start/stop of the Jack transport synced
> between the hosts, but not the tempo. This limits the use of applications
> which do make use of tempo changes on slave hosts, forcing me to copy the
> tempo map to them and run it in a DAW. As a side effect I can see the BBT
> drifting between hosts (apparently its value is computed using the local tempo
> mark).
> 
> Is there a way to solve this problem? Or am I missing something?


How about 'good old' midi (clock)? [1]

I imagine something like qmidinet [2] would be able to transmit that. Or 
you could us Pure Data (aka Pd) which also has TCP send and receive 
objects ([netsend] and [netreceive]). With Pure data you might need to 
do a bit of math to calculate the tempo, but it's quite straightforward 
(I did a Pd patch which used MIDI clock to send tempo to Yoshimi 
recently, quite unrelated to your use case but could be useful for the 
midi clock part [4]).

I honestly never tried midi clock like that with physical machines, but 
I did use Pd in the past with TCP within the same intranet and it worked 
quite well, YMMV.

Lorenzo.

[1] https://en.wikipedia.org/wiki/MIDI_beat_clock
[2] https://qmidinet.sourceforge.io/
[3] https://puredata.info/
[4] https://gitlab.com/lorenzosu/yoshimi-bpm-sync-lfos

> 
> Thanks in advance
> 
> cheers
> Francesco Napoleoni
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