Audiobus: Use your music apps together.
What is Audiobus? — Audiobus is an award-winning music app for iPhone and iPad which lets you use your other music apps together. Chain effects on your favourite synth, run the output of apps or Audio Units into an app like GarageBand or Loopy, or select a different audio interface output for each app. Route MIDI between apps — drive a synth from a MIDI sequencer, or add an arpeggiator to your MIDI keyboard — or sync with your external MIDI gear. And control your entire setup from a MIDI controller.
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Does anyone have numbers for Bluetooth vs Midi IDAM latency?
It feels like Bluetooth has slightly more latency than IDAM. And that IDAM is not that fast compared to just pluging a regular USB Midi keyboard. Am I wrong?
I'm on a M1 Macbook Air with usually a 128 buffer size.
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As near as I can measure, there is about 2ms difference between IDAM and BLE MIDI. I tested by sending MIDI out from my MacBook Pro to AUM on my iPad Air 2, then back simultaneously to the MacBook over IDAM and BLE MIDI.
IDAM was delayed by 10ms and BLE MIDI delay was 12ms. We have to account for the outbound leg, so reduce each by 5ms. That's 5ms latency for IDAM and 7ms for Bluetooth.
Not a very scientific test, but I think it's fairly close. I couldn't think of any convenient way to measure direct USB MIDI input. That would probably vary by the MIDI interface somewhat anyway.
This is very cool! Thank you for sharing. So there isn't that much of a difference between the 2. Glad I could spot it anyway
That makes me think that I'll stick to bluetooth cause it's more convenient, like it auto-connects now with my new laptop, even if the laptop goes to sleep... IDAM needs reconnecting and fiddling around Audio Midi Setup almost every time I need it.
Thanks a lot!! Super helpful to confirm intuition.
I think it always depends on the gear you are using but I am no expert I just noticed that I have absolutely no latency that I could hear on my Bluetooth midikeyboard in comparison to just plugging a USB keyboard into a hub and connecting it with lightning
@amethystswitch yes totally, I forgot to mention that my gear is an iPad (air 2 like Wim). I heard that some Bluetooth devices are better than other at handling Midi.
So, I did a little better testing. I hooked a keyboard up to the MacBook via USB and used MIDIPipe to send that output to a DAW and in parallel out to the iPad via iDAM, then back in.
There was no way to measure the direct USB latency, but this time the round-trip for iDAM took only 1ms total. The iDAM notes from the iPad recorded only 1ms behind the direct USB. The BLE Midi from the iPad was 3ms behind the iDAM Midi.
So, pretty consistent with the previous results, but now we know that compared to USB direct:
These are just indicative. I imagine results could vary based on various conditions.
Wow thanks so much Wim, this is awesome!!
May I ask, do you find the Bluetooth latency manageable? Of course that's subjective as it depends what sort of Midi inputs and how much correction we're willing to apply, but maybe in therms of feeling and flow?
Personally I find it a bit too noticeable, but again I just use it more than IDAM because of how more convenient it is.
I wonder if there's such thing as a bluetooth USB dongle of sort, smth that would make the latency much better and keep everything connected. I think I saw some USB dongle for a Midi ring once, they claimed that the Bluetooth Midi was much better. Maybe even soundcards now offer the feature. I have to research this. Of course what makes Bluetooth nice is that it doesn't require additional cables and gear, but if a simple USB dongle improves Bluetooth latency that could be interesting.
@stelvio The reason why Bluetooth latency is quite low when transferring simple low-bandwidth serial data like MIDI is that it can be consumed immediately on the receiver side and the message frames are tiny.
But even that is limited. Too much MIDI data will draw too much power from the MIDI port if 5-pin MIDI is involved so it won't work for very high polyphony, too much controller data or sysex.
Audio needs compression for the lack of enough available Bluetooth RF bandwidth (and that's also a reason why BT can run on very little battery power) and to reduce that, changes would be necessary in the BT sender and receiver themselves.
I don't find Bluetooth latency noticeable, but that's probably because I'm not much of a keyboard player. I think I might notice 4ms added latency on top of what's already there playing guitar though since I have more skill at doing that.
I don't think there's a lot you can do to reduce Bluetooth latency. And even if you could cut it in half, that difference would be less than 2ms. But no harm in looking into it.
Thanks rd2000 and Wim
sorry for the slow reply! Really appreciate your input, that was very interesting!!
Bluetooth has profiles that do NOT buffer up large packets adding latency but Apple has decided on to support those Bluetooth Profiles (yet). Bluetooth MIDI fires off of a quick packet but audio is buffered up and sent in a large packet but making Bluetooth useless for live music interop. Go figure. The Bluetooth profile that I have spent money on is AptX. Apple ain't singing on so it requires dongles to convert and "gaming headphones".
Apple's investment is in Spacial Audio to position sound after 30-40 msecs on their AirPod devices. NOTE: Battery really matters when you go wireless and audio matters less.
Thanks a lot!! Super interesting.
Also never heardf of aptx so I'm digging now.