Developer Preview 3

This is a relatively small but important update over Developer Preview 2.x. For those who were blocked in the previous release due to bugs caused by the scheduler, this release will unblock you and allow you to continue development.

If you have a previous preview installed, please uninstall it.

Key notes

• Outbound message scheduling is temporarily disabled. It was causing a number of issues in the previous preview. Once it is solid, we'll release another preview with it enabled. The API is still the same, it's just that the timestamps are ignored and all messages are sent immediately.
• Still plenty of debug code (primarily OutputDebugString and similar) in the builds. If you run dbgview64, or attach to the service process (or app process) from Visual Studio, you can see the output.
• No updates to the USB driver due to the holidays. Please use the version from Developer Preview 2.
• Defender sometimes flags the setup package, or part of it, as a threat. This is a false positive. We'll look into code signing Github releases for the future. See screen shot below for VirusTotal and Kaspersky submission results

Please see the issues list for other known issues

Bug Fixes

This preview fixes or works around a few bugs:

• Fixed: #188 Incoming KS device timestamps are 0
• Worked Around #183 as this is related to outbound message scheduling crashing in the service
• Worked Around #182 also related to message scheduling

The last two are not yet marked as fixed because they are simply worked around in this preview release. However, it's key to work around those right now for you all to be able to test the release.

New features

Service metadata parsing

• The service now parses in-protocol endpoint data and function blocks as long as there is at least one client listening to an endpoint. Right now, this information persists across service restarts. In the future, we'll be clearing this information from the cache when the device goes away. There must be an active client connection at the time of message arrival for the data to be cached. This is by design.

MIDI Console

• The MIDI console can easily request endpoint metadata and function blocks through the new midi endpoint request command. If you don't have a long-running connection open in another application, the recommended way to use this is to open one console monitoring the UMP device, and another for sending the request. Note that the console doesn't keep an active connection after sending messages, unless you schedule messages out into the future. Otherwise, only when you are monitoring an endpoint is the connection maintained.
• Function blocks are displayed in the endpoint properties
• Endpoint Device Watcher updated to display more information about what has changed

Enumeration API

• The Enumeration API has been updated to provide more information about which properties have changed in the Watcher Updated event.
• There have been additional properties added to the MidiEndpointDeviceInformation class, as well as an update to the Function Blocks vector to change it to a map, indexed by block #

Installation

Uninstall any older version of Windows MIDI Services from your apps -> installed apps in settings. You do not need to uninstall the USB driver.

Unzip the Windows.MIDI.Services... zip file somewhere and run the contained exe installer. This will install the API, Windows Service, and MIDI console. Keep the installer around so you know which version you last installed. This is needed for bug reports.

If you want to communicate with USB devices, install the attestation-signed USB driver from Developer Preview 2. Requirements for the driver are documented there. Primarily, you need to be running an Insider Canary build of Windows 11.

As always, discussions on Discord are welcome, as are bug reports here.