Realtime Engine

Where StreamAnalyzer listens, the RealtimeEngine plays.

It is the transport-and-playback side of libsonare's realtime surface. It handles tempo, clip scheduling, a metronome, automation, and metering telemetry.

Use it when you are building a playback engine rather than just a live analyzer. For the API, see Realtime and Streaming.

Transport: the playhead and tempo

Transport is the playback clock — play/stop/seek, the current position, loop points, and the tempo that everything else is timed against. A clip scheduled "at bar 5" or an automation point "two beats in" only has meaning relative to the transport, so the transport is the shared timeline the whole engine reads from.

Clips and scheduling

The engine plays clips — buffers of audio placed on the timeline at scheduled positions. Scheduling means deciding when a clip starts and stops relative to the transport, so playback can be assembled from many pieces rather than one continuous stream. This is how an arrangement, a backing track, or a rhythm-game chart is driven.

ENGINE · LANE MIXERIDLE

The engine lane mixer — faders and mutes inside the playback engine

Three MIDI clips loop through the realtime engine: each track occupies a lane with its own channel strip. The faders call the strip setters and the mutes call setSoloMute — every band below is the engine’s actual per-lane output, re-rendered through renderOffline as you move the controls.

Lead fader

0 dB

Bass fader

0 dB

Drums fader

0 dB

Mute lead

Mute bass

Mute drums

Metronome

A metronome generates click events locked to the transport's tempo and meter — useful for monitoring, recording, and lining up performance. Because it is derived from the same transport clock, it stays in sync with clips and automation automatically.

Telemetry: watching a realtime graph

You cannot inspect a realtime audio callback with a debugger without breaking timing. Instead the engine emits telemetry — periodic snapshots of meters and state — that your UI reads on a normal (non-audio) thread. This keeps the audio path untouched while still letting you draw level meters, a goniometer, or transport state.

How libsonare models the engine

RealtimeEngine (driven by EngineController) owns the transport, schedules clips through ClipPlayer/ClipSchedule over ClipAudioBuffer storage, generates clicks with Metronome (MetronomeConfig → MetronomeEvent), and plays automation back on the mixer graph. Metering is surfaced through a MeterTelemetryTap producing MeterTelemetryRecords and a general Telemetry channel (TelemetryType/TelemetryErrorCode) that a UI reads off the audio thread. The whole engine is real-time-safe and runs the same offline (bounce) and inside an AudioWorklet, including freeze and capture paths.

Related: Realtime and Streaming, Streaming Analysis, Realtime Safety, Automation and Metering