Audio and DSP

Flow has a real audio stack: typed sample rates, frames, buffers, oscillators, filters, envelopes, delay lines, a graph scheduler, and real-time safety checks.

Requires FLOW_HOST=python.

Run it

FLOW_HOST=python flow audio program.flow           # compile and run with the audio backend
FLOW_HOST=python flow compile-audio program.flow   # compile only

The modules

ls lib/stdlib/audio/
cat lib/stdlib/audio/README.md

Units are typed on purpose. Build a sample rate with sample_rate_48000() rather than passing a bare number, and convert with ms_to_samples, samples_to_seconds, and seconds_to_samples. That is the whole point of those wrappers.

Shape of a voice

import "stdlib/audio.flow"
import "stdlib/audio/oscillators.flow"
import "stdlib/audio/envelopes.flow"
import "stdlib/audio/filters.flow"

Read a complete one before writing your own:

cat examples/audio/fm_voice.flow
cat examples/audio/karplus_strong.flow
cat examples/audio/drum_machine.flow
cat examples/audio/adsr_vs_click.flow      # why envelopes exist

Real-time rules

Inside an audio callback: no allocation, no locks, no file or console I/O, no unbounded loops. Allocate buffers up front and hand them in.

audio/safety.flow and docs/language/ cover the real-time profile. Use the delay feedback guard pattern from examples/audio/delay_feedback_guard.flow for any feedback path, because an unguarded feedback gain above one produces a signal that grows until it clips or becomes NaN.

Verify by measuring, not by listening

Render to a file and check the numbers.

ls examples/audio/*probe* examples/audio/*verify*
grep -rn --include='*.flow' "function verify_" lib/stdlib/audio/verify.flow | head

Useful assertions:

• peak and RMS fall inside an expected range;
• no sample is NaN or infinite;
• no sample exceeds full scale, unless clipping is the point;
• a sine at a stated frequency has its energy in the right bin;
• an envelope with a proper attack has no discontinuity at note start, which is what adsr_vs_click.flow demonstrates.

Return a distinct non-zero code from main per failed check.

Reporting

State the sample rate, the block size, the duration rendered, the peak and RMS, and the exact command. If you produced a WAV, give its path. Never say a sound "sounds right"; you did not hear it.