Every release adds its own entry here, newest first: what changed, in the words of what it does. A release is tagged <major>.<minor> on main - 3.0, never 3.0.0f001 - and the builds between releases carry their deployment letter and build number instead (etc/tools.sh's short(), dx::version).

3.0

The first stable release since 2.5, and the release this documentation describes.

The Windows kernel driver

kernel/wdk grew the whole WDM audio path: a PortCls adapter publishing one WaveRT subdevice per audio pin and a DMus subdevice per MIDI pin (dxd::portcls), over a USB device of its own - raw URBs, isochronous pipes, the configuration walked by the same dx::usb::audio::configure user mode uses, a boot() hook for a product's firmware handshake. The tick runs on a high resolution EX_TIMER, aligned to the bus frame counter, and the device's rings are mapped into every proxy client, each with a cursor of its own. Surprise removal, the hardware released in conclude() ahead of the remove, and the license gating the published subdevices are part of it.

Streaming

The streams of one device that always stream together form a group with one realtime thread (dx::stream::group), and the group owns every session resource. Completions stopped being a data point: the tick submits, writes and reads by the frame counter alone, a lead ahead of and behind the wire. A ring is reset by its host at its session's start and by nobody else - a service client, a pod, a proxy client or a kernel client attaches to a running ring by seating a dx::stream::cursor. The sample converters are keyed by the whole format, resolution, endian and alignment included (dx::stream::sample), and a clock's lock delay is waited out on both platforms.

Values and their stores

A promoted with a server asks it first and is born with its value otherwise - a value that could be asked with neither no longer compiles (dx::promoted). The driver's log became a preference promoted on the store and serializes like a stream desc, through the member list sinks of dx_serialize.h, so the registry and the property list both hold it resolved rather than as one opaque word.

Licensing

dx::license is one class for user mode and the kernel on every platform: it reads the certificates' DER, verifies the signature against the product's embedded root with its own SHA-256 and RSA, and evaluates type and constraints. A license binds to the device's serial number, the machine's or an ethernet address; the platform supplies the store's candidates and those identities alone - keychain, CryptoAPI, and in the kernel the registry and WMI.

The Windows user mode side

The service hosts a device tree and serves its streams over shared memory and the dxd pipe; the ASIO driver runs as its client or straight on the kernel driver, and registers itself when a device arrives - never an installer's job. The WASAPI client, the Windows MIDI Services client and the match dictionaries of both came with it. The installer is WiX 6, a merge module and an .msi without DIFx, the driver packages installed by dx::install::parser as custom actions.

MIDI

dx::midi speaks the Universal MIDI Packet: the ring of packets, the encode and decode of the MIDI 1.0 byte stream, and the group inside the word. CoreMIDI carries UMP since macOS 11 and Windows MIDI Services from the start, so both buses hand whole packets at their own timestamps.

macOS

A class compliant USB audio device is held by Apple's usbaudiod, and only a root process may take it away: the doorman daemon does exactly that and nothing else, so the driver itself stays unprivileged (dx_usb_capture.h, dx_xpc.h, dx_daemon.h). The CoreAudio server publishes a data source control per pin.

Tooling and documentation

The test harness grew its nested command line, the streaming monitor with loopback, pattern-test and generator, unit test rows per bus and a driver level run with surprise removal. etc/release.sh performs a stable release end to end - stamp, build every platform, notarize, publish, merge, tag and bump - and rehearses it with --dryrun. The headers carry their own documentation, the Doxygen run is warning free, and this page exists.

2.5

2025-08-26. The promoted preference gained its type safety and its alignment against the current value; a stream's sync reference reached every bus; the CoreMIDI and CoreAudio clients followed the stream layer's start and halt; a USB transaction whose size differs from the ring's line is carried.

2.4

2025-08-07. The CoreAudio server plugin's property and locking corrections, ARM64 and ARM64EC projects, and a pass over the headers' includes and their documentation.

Before 2.4

The repository's log is the record: git log 2.4 and the tags of the branches it was released from.