I noticed a Midi Clock Jitter Bug with a repetative pattern.
Create empty project.
Add midi track.
Transport/Project Synchronisation Setup :
Set Midi CLock Destination to a Midi-Port
Uncheck MidiClock Follows project.
Uncheck Always Send Start Message
Uncheck Send MIDI Clock in Stop Mode
Set Tempo to 100 BPM
Get an Arduino Micro and build a programme that reports the time between midi clock pulses, start Serial Plotter in the arduino software, and the you get these graphs.
(there are other ways to analyze midi clock data, but I’m building an analog BB-delay with midi sync, the Arduino is doing the syncing and clock generation for the BB-chip, that’s the reason for the Arduino)
[Cubase MIDI Clock Graph]
And see, there is very clear repetative jitter pattern (starting from clock pulse 26 in the graph), always in a cycle of 6 clock pulses. The blue line is a counter resetting every 6 clockpulses, for reference.
The first 26 pulses in the graph show how stable Cubas Midi Clock can be, unfortunately this short period of nearly a Bar only takes place when hitting Play and then about every 6 Bars.
@100BPM, the average time between 2 pulses should be 25000 micro seconds (uS)
in the graph we have:
x-axis : the clock pulse count, every gray line represents a clock pulse
y-axis (for red line): the time since the previous pulse, in micro seconds.
clock-pulse 1 = ~25000 uS : ok
clock-pulse 2 = ~26000 uS : 1000uS too long
clock-pulse 3 = ~24000 uS : 1000uS too short (compensation?)
clock-pulse 4 = ~25000 uS : ok
clock-pulse 5 = ~25000 uS : ok
clock-pulse 6 = ~25000 uS : ok
So what we see here is a huge variation in Midi tempo within the time of a beat.
1000/25000 = 0,04 = 4% jitter up an down thats 8% speed difference!
This explains why my Arturia DrumBrute’s BPM display is always jumping up and down when synced to Cubase Pro 9.5. I also checked Cubase Pro 8.5, and it shows the same problem.
For reference I also checked the Midi Clock jitter of my DrumBrute, and as the thightness of the machine does suspect, it hardly shows any jitter.
This is the amount of jitter I expected Cubase to have, and it seems Cubase is able to do this, but for now only maintains this tightness for 3 beats every 6 Bars…
[DrumBrute MIDI Clock Graph]
As you can see in the DrumBrute graph:
Max 25050uS and Min 24950uS that means 50/25000 = 0.002 = 0,2% jitter.
That’s 20x tighter then Cubase!
Both my RME and MOTU gave the same timing results, so that would probably exclude driver issues.
The clock starts Jittering when the MIDI clock is synced to audio or sequencer…
If you change the setting:
- check Send MIDI Clock in Stop Mode
You can see MIDI clock is much more constant when Cubase is stopped, instead of playing and the distinct pattern in the Clock Jitter also disappears when Cubase is stopped.
Because of the steady repetition of this timing deviation, I think there must be a calculation error in the code or something like that.
Counting from 0 or counting from 1…Mayby be a rounding problem, or some other stupig mistake.
I don’t know, what I do know is that MIDI-sync has not been working properly for a while, and this is is the reason.
Please check this, shouldn’t be too hard to fix.
Tight MIDI would make a lot of people happy, it actually is the basics of a sequencer.
Cubase Pro 9,5,20