jammr Forum

captaincancel
Yeah, I'm a little confused by the BPM/BPI metronome and what it means from an algorithm/technical perspective.

Is it used just as a guideline for the room? I've seen people say “you have to follow the click” which totally makes sense to me, but is that same BPM/BPI used at all in the latency compensation mechanics of Jammr or is it just to give some structure to the room?

When I say it goes out of whack, what i mean is that players slowly drift out of sync with each other. Based on your post, I think it might help to revisit how JAMMR works.



In order for JAMMR to keep us in sync, our metronome needs to be accurate. The metronome provided by Jammr works. Using a VST drum machine (see https://www.powerdrumkit.com/) works. But if you have a physical drum machine, and manually set it to match the BPM of the session, it will drift out of sync because the clocks are not 100% perfect and even the smallest variance will add up over time. And until the MIDI clock coming out of the JAMMR MIDI out port is fixed, you can't keep that physical drum machine in sync.

eb_liveDrums
In order for JAMMR to keep us in sync, our metronome needs to be accurate. The metronome provided by Jammr works. Using a VST drum machine (see https://www.powerdrumkit.com/) works. But if you have a physical drum machine, and manually set it to match the BPM of the session, it will drift out of sync because the clocks are not 100% perfect and even the smallest variance will add up over time. And until the MIDI clock coming out of the JAMMR MIDI out port is fixed, you can't keep that physical drum machine in sync.

Right, but if everyone in the room turns off the Jammr metronome, and somebody is streaming a reliable drum machine to the room, can a tight jam be realized? I think so: I had a drum machine going and most players turned off their metronomes I would imagine: I mean, what I heard from a bass player and guitar player (and later, a keyboard player and guitar player) it sounded in time to me, at least for a while, 3-5 minutes, until they lost focus or left (or my drum machine was drowned out by loud guitars joining in).

Because I don't believe that the metronome is synchronous across all Jammr sessions, i.e. if 5 people are in a room and everyone fed the metronome from Jammr into a return channel somehow, I don't think we'd hear 5 synchronized metronomes at all, and I'm not talking about intervals either, I don't think we'd hear the beats themselves in sync.

Edited captaincancel (April 18, 2020 14:56:41)

captaincancel

I'd be down to try this, win or lose.

julian_vickers

I'm going to play around with this today:
https://forum.jammr.net/post/4565/

What time it? I'll tell the family to expect my absence of it's not one of those “non negotiable” times.

I’ve tested this, and if everything is configured properly then yes, the metronomes are in sync when they are combined. Heres the thing though, if you check the box in audio config to monitor your input, it throws off the sync of what you send, it gets delayed something like an 8th note.

eb_liveDrums
I’ve tested this, and if everything is configured properly then yes, the metronomes are in sync when they are combined. Heres the thing though, if you check the box in audio config to monitor your input, it throws off the sync of what you send, it gets delayed something like an 8th note.

This… actually makes sense as far as the delay. Probably could be coded another way if that's the case, but I can see how the delay could happen.

As far as ‘combining metronomes’ - are you talking about Cap'n's post above about streaming a reliable drum machine into a session? If that works that would be a pretty good workaround.

julian_vickers
What time it? I'll tell the family to expect my absence of it's not one of those “non negotiable” times.

It was too nice out, went for a long bike ride instead.

eb_liveDrums
I’ve tested this, and if everything is configured properly then yes, the metronomes are in sync when they are combined. Heres the thing though, if you check the box in audio config to monitor your input, it throws off the sync of what you send, it gets delayed something like an 8th note.

Very interesting. I wonder how he's doing that. I was thinking of Network Time Protocol, and how it will periodically sync back to a clock source (time.windows.com, etc.) while also capturing drift rate to determine how often to check back… turns out there is a really interesting paper on that from 2016 (using GPS) for a “global metronome”, but I haven't seen any follow-up projects online.

Exhibit A: https://forum.jammr.net/post/2317/

"It is not necessary to play on jammr's metronome click as long as you
are playing at jammr's tempo (BPM). That means you can disable the
metronome if there is a drum pattern playing at jammr's BPM - and the
drum pattern doesn't need to start on jammr's metronome click."

I think this is because Jammr's using this to calculate delay compensation when streaming.