As computers have become central components in many MIDI systems, USB has become the most widely used protocol for transporting MIDI data. With the introduction of MIDI 2.0, the USB Implementers Forum’s USB MIDI 2.0 working group, headed by members of the MIDI Manufacturers Association (MMA) and the Association of Musical Electronics Industry (AMEI), have updated the USB Class Definition for MIDI Devices. This spec defines how USB transports MIDI data.
The key to the updated spec is use of the new Universal MIDI Packet to support MIDI 2.0’s new functionality, while retaining backward compatibility with MIDI 1.0.
Highlights of operation over USB include:
·Better support for deterministic, high-speed throughput (up to hundreds of times MIDI’s original speed)
·Old and new devices work with any operating system that supports the updated USB Class Definition for MIDI Devices
·As with the previous version, no drivers needed for compliant devices
·Supports up to 256 MIDI Channels in 16 Groups of the new Universal MIDI Packet
·Can provide more accurate timing for dense MIDI streams
·Devices can run multiple Endpoints to use more than 256 Channels
·Over time, simpler to implement than USB MIDI 1.0
·Enhances the use of MIDI 2.0 mechanisms including MIDI Capability Inquiry (MIDI-CI)
·Supports both MIDI 1.0 Protocol and MIDI 2.0 Protocol Data
·Devices can declare UMP Group IN/Out pairs for use by MIDI-CI
·Devices can declare that more than one UMP Group is used for a shared or related function.
·Added Bandwidth descriptors for more predictable use of higher speeds.
·Added support for Interrupt transactions as well as Bulk (USB MIDI 1.0 uses Bulk only) for more deterministic control over jitter and throughput.
According to Mike Kent of the USB-IF Audio Working Group and MMA Technical Standards Board, “The new spec provides operating system manufacturers, like Apple, Microsoft, Google, Linux, and others, a clearly defined path for moving forward with MIDI 2.0.”
As with MIDI itself, the new USB Class Definition has been a collaborative effort, involving multiple companies from around the world. In conjunction with its members, the MMA and AMEI will continue enhancing the MIDI 2.0 specification, and assist manufacturers with incorporating MIDI 2.0’s features into the next generation of music gear.
Details on the USB Class Definition for MIDI Devices specification are available from the link below.
We encourage all MIDI developers to download the specification and we will adding articles to MIDI.org with more details on the USB-MIDI 2.0 specification soon.