Bluetooth MIDI? What about latency?
Many people (including engineers) who did not try Bluetooth MIDI assume a lot of things about latency with MIDI over Bluetooth. MIDI is a serial based protocol that has been developed in the early 80s. It is not amazingly fast to begin with.
Bluetooth has been rapidly developing over the last decade. It handles a few megabits per seconds easily. That is why it is easy to say that MIDI over Bluetooth is capable of offering a professional low latency solution for musicians and producers. Both on stage and in the studio.
It is even more easy to say this as a manufacturer. Feel welcome to watch this 2 minute video by Roger Linn. Mr. Linn, the legendary designer behind the LM-1, MPC and LinnDrum, talks about WIDI Master and his MPE-based Linnstrument by Roger Linn Design.
Please note, this is not a paid endorsement. Neither did any member of the CME team asked Roger to create this video. He just bought it. Liked it. And shared it.
Wireless MIDI: Basics
Before we go into details and more sophisticated matters, let's address some main ideas about BLE MIDI (Bluetooth MIDI).
- Bluetooth MIDI is not Bluetooth Audio and does not experience the same latency issues. They are two completely different technologies.
- Latency is normal. It occurs in the human hearing and in the communication between an audio interface, computers, midi controllers, monitor speakers, and so on. Everything has latency.
- Conversion time is negligible. The latency between two WIDI devices is as low as 3ms. This is absolutely inaudible to the human hearing. It is even lower compared to the internal latency of many MIDI devices, software and apps.
- MIDI transmits data at a standard speed 31.25 kbit per second via cable. WIDI devices using Bluetooth 5 go up to 400 kb/sec.
- When talking about latency, you have to take your entire setup in account. Consider that the entire (or round latency) of your setup consists of many devices and your Bluetooth MIDI connection is just one of them. The round latency of a MIDI setup can easily be 15ms in total.
A tiny word on MIDI terminology
As you might know, the history of MIDI technology incorporates widely used terms as master and slave. Although the term master is not causing any real issue, the word slave can trigger undesired feelings and emotions to a large group of people.
Following requests from the Community of MIDI Enthusiasts, it is intended to change the terminology to a more modern form of communication.
That is why, with Bluetooth MIDI, we rather speak about central and peripherals when discussing Bluetooth connections. And with USB MIDI, we rather talk about hosts and devices.
As the previously used MIDI terminology trivialise something quite horrendous associated with institutional racism and colonisation, the purpose is to no longer use the term slave. Although this might be a bit confusing to you in the beginning, it only takes a short while to adjust. Read this article for a better understanding.
Let’s return to the fun part. Let’s talk about BLE MIDI and of course…..latency!
Latency is just a number…
There are a lot of claims being made about latency and especially the ability of being able to really notice it as a human. Let alone link it to a specific part of your system. There are musicians who play their instruments based upon the limitations of that device. Latency can be just one of them. Therewith it becomes part of the deal.
Of course, latency is an important metric when it comes to music production and performance. Latency for Bluetooth MIDI does not stand upon itself. It depends on the environment and the connected devices.
As with Roger Linn, one of the other early adopters of WIDI was the amazing Jean-Michelle Jarre. Again, there has been no request from CME towards JMJ. Nor did we pay him to say a few nice words. He simply bought it. Liked it and reached out to us to congratulate the CME company and its engineers....
Smart Connectivity Algorithms
To proceed with the previous paragraph about latency, it is important for a complete understanding to look at the bigger picture.
When you look at your entire system, it is complex for you as a musician or producer to pin-point latency to a specific part of the system. How are you able to say the latency you experience from your monitor speakers are caused by either MIDI communications or audio conversions? Or delays in translation by your operating system?
That is why it is best to keep this simple and not get stuck in one single metric. With Bluetooth MIDI, the latency metric is not a given in every situation. It is not one solid number. The performance depends on multiple factors. That is why, you should be careful with reading a metric from a page and assuming it says it all.
Try it yourself!
That is why it is recommended to try it yourself. Experience the performance with different setups in different environments. Following you can make your own decision based on real life experiences.
Another important factor is jitter. It is more or less the variation in latency. In the end, a proper musician can play with a stable latency. That is why jitter is also a very important metric. Especially when it comes to real time MIDI clock and sync purposes.
Our engineers are constantly working to improve WIDI's firmware and especially the jitter performance. WIDI uses a collection of smart algorithms to select the best performing frequency at a given distance between devices. This is what is called Adaptive Frequency Hopping. In short, WIDI is able to switch frequencies to keep delivering the best performance.
The entire collection of algorithms used is called SCA. Or Smart Connectivity Algorithms. With SCA, WIDI performance is optimised in any given situation. SCA stands for Dual Role Automation, Automatic Pairing Mode, Smart Hub Functionality, Latency Reduction Optimisation and Range Performance Optimisation!
The difference between a MIDI cable and BLE MIDI
First of all, with Bluetooth MIDI latency is always a bit higher compared to a regular MIDI cable.
That said, you can question yourself if you would be able to distinguish WIDI Master from a standard MIDI cable in a double blind test. We have noticed that this will always lead to the same discussion about latency.
This discussion is quite similar to the one we have had in the start of streaming and the download days involving MP3s and WAV files. Or that one of the supreme quality of vinyl over anything else….it is ongoing, never ending and also very much part of the process of developing innovating technologies.
Bluetooth MIDI and latency on iOS & Mac
When talking about latency of the WIDI technology you’d have to keep in mind we measure latency by using an oscilloscope. It is measured between two WIDI Masters. The lowest outcome is 3ms. The highest is 10ms. We measure an average on 5ms to 6ms.
The latency on iOS and macOS came from the limitation of the Bluetooth connection interval. This is a rule set by Apple. On iOS it is 11.25ms minimum. On macOS it is 7.5ms minimum.
Please note that these are “intervals” and not “latency” metrics. These intervals can cause latency and jitter due to the limitation of that buffer.
Bypass Limitations of macOS and iOS
The main reason for this limitation is because Apple has no intention to place Bluetooth MIDI at a high priority compared to other more common services. Thus if you connect any Bluetooth MIDI device with iOS or macOS, you cannot get the connection interval lower than above mentioned limitations.
If we break away from the iOS and macOS Bluetooth connection interval, two WIDI Master can set itself with shortest interval that Bluetooth 5 supported. In this way, we can reduce the latency significantly.
Also, in the design of macOS it is integrated to "kill" any unused BLE MIDI connection. It is designed this way, because macOS does not prioritise Bluetooth MIDI. It prioritises Bluetooth for audio and other data. Bluetooth MIDI is simply not that important for Apple...
To bypass limitations of iOS and macOS an interesting option is WIDI Uhost or WIDI Bud Pro. It will also allow you to pair automatically, instead of manually setting your BLE MIDI connection every time..
Bluetooth MIDI Groups
After releasing the basic Bluetooth firmware for all WIDI devices, the community started asking for more advanced solutions. This resulted in the provision of WIDI groups via the WIDI app and Bluetooth MIDI groups via the group auto-learn mode.
Basically, if you use only WIDI devices in a group setting, you can set your WIDI group up manually via the WIDI App. If you want to add other Bluetooth MIDI devices, you can do this via the group auto-learn mode.
Group connection is a relatively new feature that the community has been asking for. You can add up to 5 Bluetooth MIDI devices (including WIDI) and create 1-to-4 MIDI split and 4-to-1 MIDI merge setups.
It is a suitable solution if you want to control multiple peripherals easily from one device. Of course there are some limitations....
Syncing multiple MIDI devices wirelessly
In group mode, you can send any kind of MIDI message, including MIDI clock. This allows you to synchronize multiple MIDI devices in a sequencer-like arrangement. That said, in the wired MIDI world, syncing MIDI devices can already cause jitter, it's no different in a wireless MIDI situation.
When working with a direct connection between two WIDI devices, the transfer of the MIDI clock is rock solid. No issues have been reported at this stage. When switching to group mode, we received a limited number of reports of jitter issues when syncing multiple devices wirelessly via MIDI clock.
The problem is, we can't reproduce this exact problem. That doesn't mean the problem doesn't exist. WIDI groups have higher jitter compared to a direct WIDI-to-WIDI connection with two WIDI devices.
When group mode is enabled, the connection interval is extended to allow scanning while already exchanging with connected device(s). A larger connection interval results in a higher jitter.
Therefore, WIDI groups are limited to a maximum of 4 peripherals. At this number, the latency and jitter are still acceptable.
Besides this, it is necessary that you connect all members of the group. Otherwise your central device will continue to scan for the missing group member(s), adding unwanted jitter.
If you are experience issues in group mode, please do reach out to us. We would like to understand better where this comes from and maybe find a way to solve it.
The test results of syncing via Bluetooth MIDI
As mentioned, in our test environment we are able to add multiple devices via WIDI groups and send MIDI clock messages and synchronize multiple devices wirelessly with acceptable jitter.
In the table below you will find the BPM variation in groups versus direct. As you can see, the variation (jitter) increases as the BPM increases. This is similar to a wired situation.
Also, the jitter (in BPM) is higher in group mode compared to the direct WIDI-to-WIDI connection. This is also acceptable from our side.
Reproducing your setup and environment...
It seems that jitter issues are related to a combination of specific sequencers and BLE MIDI. This means that in some cases it occurs, but in many cases it does not. It could be in the way the sequencer structures its timestamp when using MIDI clock.
Since it's impossible to recreate every setup and environment, it's really hard to say. That's why you get full transparency from our side.
Again, this is a fairly new technology. It's just not perfect for all use cases. Once a new feature is released, it has pros and cons based on the limitation of the technology. It really depends on your unique application.
That is why we also accept returns. Hassle-free. If WIDI is not good enough for your application, you will get a refund without any problem. If that is the case with you, please contact us via support page.
Video test results
As mentioned, Bluetooth MIDI groups provide a great solution for many, but not everyone. As you may know, syncing multiple devices via MIDI can already be a challenge in the wired world. That said, in our test setup it is certainly possible to synchronise multiple MIDI devices via MIDI clock.
In this setup, three (3x) WIDI Masters were lined up in a WIDI group. The MIDI clock was sent from the Yamaha QY100 via the WIDI central unit. Two WIDI peripherals receive the clock as shown in the screens through two different music software programs.
Of course, our engineers are constantly improving the Bluetooth MIDI standard and the WIDI firmware. That said, at this point we think we've reached the limits of what is possible with Bluetooth 5.
That is why we are always researching new angles and technologies.
Make decisions based on real life experience..
You are perfectly capable of making your own decision. If latency is the only metric you make your decision on, and cables work for you, you just stick to your cables. Or at least wait until you and your musician friends can test our Bluetooth MIDI solution in real life at your local dealer. That is fair enough, right?
In the other hand, if you are interested in getting rid of those cables, advanced midi connectivity, app based cable management and wider range plus freedom of movement with midi (like on stage), then Bluetooth MIDI solutions might be of interest for you.
Take a look at this great video by the amazing Shook and partner Juliet. This time, the videos made by Shook all are advertisements. This means, Shook got paid to create them. And it was worth every single penny!
Facts about Bluetooth MIDI
With the current BLE MIDI solution as developed with CME’s WIDI it is possible to reduce latency between two WIDI devices using BLE 5 to 3ms. When looking at a stable jitter it is considered that a 4–6ms latency is more accurate.
If you want to find out more about WIDI Master and latency: go read this!
Bluetooth MIDI is the standard as developed by Apple and approved by the MIDI Association already 5 years ago. Many industry icons including engineers from Moog, David Smith, Yamaha, Roland, Korg, Apple, Google, Microsoft etc. worked together to verify this standard.
Learn more via the MIDI Association!
There are many professional keyboards and synthesizers already equipped with Bluetooth MIDI features. Tens of thousands professional musicians use it on the stage or in the studio for over several years. If you search on Google, you can find many examples.
CME implemented this Bluetooth specific central role MIDI technology in the renowned Xkey Air (2015) and WIDI BUD (2016).
Up until this day CME rarely receives complaints by professional musicians about instability of connections and latency. Mainly issues are caused by settings, obstacles and also limitations of MIDI devices and the architecture of operating systems.
That is why, as a fact, MIDI over Bluetooth has already been approved over the time and proven to work by over 4 years of usage.
Let's do another Shook celebration!