How to improve midi timing?

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Moderndayblue
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How to improve midi timing?

Post by Moderndayblue » Wed Jun 19, 2019 3:43 am

How do you improve the midi timing over Bluetooth?

I've tried the record adjust to no avail.
I've configured my iPad to connect to my iPhone via Bluetooth to use it as an external sound source.
Midi notes hang quite often and note dropouts do occur even via my usb midi interface.

Any suggestions?

Thank you in advance.

Corey W
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Re: How to improve midi timing?

Post by Corey W » Wed Jun 19, 2019 6:52 am

I use a Korg nanoKey and there is generally no 'noticeable' latency when recording MIDI over Bluetooth.
What interface are you using?
Have you tried an external device other than your iPhone?

Moderndayblue
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Re: How to improve midi timing?

Post by Moderndayblue » Wed Jun 19, 2019 7:29 am

As mentioned previously I'm using both the iPhone as an external midi module
running various synths and triggering some of my external instruments
through a usb midi interface via an external midi hub then recording
them back into Auria Pro as audio.

I had thought that the usb hub added to the latency
but through further testing I found that it didn't.

The problem is not the sound making apps themselves.
The problem is that the midi communication isn't working as it should,
or should I say as expected.
It's no where near sample accurate and the latency is abysmal.

I had found an app called midipace and after reading up on it
discovered that it's good for removing MTC jitter but naught else.

What does Auria Pro sync it's midi signals too?
Does it sync the midi to the sample rate or does it freewheel?

The apps that I have tried are midimittr and web Midi for accessing Bluetooth.
I had found on another forum that both midimittr and Apollo midi use the same protocols.

I tried running two instances of midimittr,
one on the iPad and one on the iphone

I also tried Auria Pro's bluetooth midi to the iPhone midimittr and web Midi
which produced the same results.

If it can't be done without the latency exhibited then I'll be able to stop testing the
midi side of things or I will try another app and check for further improvements that way.

Thank you for replying.

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Rodolfo
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Re: How to improve midi timing?

Post by Rodolfo » Wed Jun 19, 2019 2:30 pm

I don’t know the exact latency value you are measuring, but as a general rule Bluetooth MIDI has some inherent latency that can or cannot be suitable for different configurations depending on the intended use.
I can use MIDI bluetooth for triggering some pad/strings sounds with no “noticeable” latency as Cory mentioned, but I find it not appropriate for percussion sounds or for playing piano where the touch is critical for a pleasant performance. I can tolerate the latency of a buffer size of 128 at 44.1KHz (about 2.9ms + the system overhead latency), but I find it unpleasant to try to play piano with a buffer of 256 (5.8ms + system overhead) and totally unacceptable with a buffer of 512 (11.6ms + system overhead).

MIDI over Bluetooth latency has typical values of more than 20ms depending on several factors, so as mentioned, it can be fine for some specific use but totally unacceptable for other certain situations.

I have also used Midimittr in some occasions with several hosts, but the latency experienced is something not specific of Auria Pro in my opinion, it’s just the inherent latency of a bluetooth connection.

I can’t comment on the dropouts you mention using a USB hub, I haven’t experienced such an issue with my controllers and keyboards with Auria Pro using an USB hub.

Moderndayblue
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Re: How to improve midi timing?

Post by Moderndayblue » Thu Jun 20, 2019 1:14 pm

Okay, you've answered my question in regards to the Bluetooth midi.
It still is the best way to connect two iOS devices so that one can use
an iPad as a main audio and midi recorder and off loading
some of the synths and modules onto a spare iPhone.
Once the audio from the iPhone is recorded back into Auria I can
use the audio quantise function to tighten up the grooves.

Yes, Bluetooth midi has noticeable latency in either direction
but I was hoping there was a midi latency adjust so that at the
very least it starts off on the beat rather than almost a 32nd after,
which is my way of saying approximately 1419 samples late which is the record adjust
value that I use now for both external and internal midi with IAAP.

All of the Bluetooth connection apps that I've used so far all exhibit
the same latency so I can rule that out now, thank you for confirming that.

I've been getting quite a few hung notes both on Bluetooth and via the direct usb midi interface.

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