# Audio engine requirements

## Real-time callback rules

The callback must not allocate/free memory, lock blocking mutexes, perform
filesystem/network/console I/O, log, load plugins or samples, call GUI APIs,
or wait for another thread.

Use preallocated buffers and bounded work. Publish parameter and graph changes
through a documented real-time-safe mechanism. Verify atomics are lock-free
where required on the target platform.

## Processing model

Process a bounded number of frames per block. Do not assume a fixed block size
unless the backend guarantees it. Define maximum frame and event counts and
safe behavior when those limits are reached.

The initial milestone is offline processing, then a test oscillator -> gain ->
meter/output graph, then a hardware backend.

## Clock and transport

Audio sample position is the authoritative playback clock. Use integer or
rational timeline representations to avoid cumulative floating-point drift.
Define tempo-map conversion and behavior at tempo changes before implementing
tempo automation.