flutter-soloud-synthesis

name	flutter_soloud-synthesis
version	1
description	Teaches how to generate audio without assets in flutter_soloud using loadWaveform() with the 9 WaveForm oscillators, runtime setWaveform*() tweaks, speechText() (built-in robotic TTS that creates and plays a source), and SoLoudTools.createNotes(). Use when the user asks for a tone generator, beeps/alerts, a keyboard/instrument, synthesized sound effects, or text-to-speech without audio files.

Synthesis: waveforms and speech without assets

flutter_soloud can synthesize audio with zero files. SoLoud.instance.loadWaveform() creates an AudioSource from an oscillator (not a stream to "set" — there is no setSource/setUrl like audioplayers; you create a source, then play() it). The returned AudioSource is reused and disposed exactly like one loaded from an asset. Runtime tweaks (setWaveform*) act on the source, so they affect every playing instance of it.

Minimal example

import 'package:flutter_soloud/flutter_soloud.dart';

Future<void> beep() async {
  if (!SoLoud.instance.isInitialized) {
    await SoLoud.instance.init();
  }

  final tone = await SoLoud.instance.loadWaveform(
    WaveForm.sin, // oscillator type
    false,        // superWave
    1.0,          // scale
    0.0,          // detune
  );
  SoLoud.instance.setWaveformFreq(tone, 440); // Hz

  final handle = SoLoud.instance.play(tone); // sync, returns SoundHandle

  // ... later
  await SoLoud.instance.stop(handle);
  await SoLoud.instance.disposeSource(tone); // required: it's an AudioSource
}

The API shape

Loading

Future<AudioSource> loadWaveform(
  WaveForm waveform,
  bool superWave,
  double scale,
  double detune,
)

Positional args, all required. superWave combines several detuned oscillators for a fatter sound; scale and detune only matter when superWave is true. Throws SoLoudNotInitializedException before init().

WaveForm enum (exact names, lib/src/enums.dart)

square, saw, sin, triangle, bounce (abs(sin)), jaws (quarter sine, rest quiet), humps (half sine, rest quiet), fSquare ("Fourier" square, less noisy), fSaw ("Fourier" saw, less noisy).

Note the casing: fSquare / fSaw — not fsquare/fsaw (the upstream docs page lists them lowercase; the code is authoritative).

Runtime tweaks (all void, all take the AudioSource, not the handle)

Method	Effect
setWaveform(AudioSource sound, WaveForm newWaveform)	switch oscillator type
setWaveformFreq(AudioSource sound, double newFrequency)	frequency in Hz
setWaveformSuperWave(AudioSource sound, bool superwave)	toggle super wave
setWaveformScale(AudioSource sound, double newScale)	super-wave scale
setWaveformDetune(AudioSource sound, double newDetune)	super-wave detune

These change live playback — call them on slider changes; no need to reload or stop.

Speech

AudioSource speechText(String textToSpeech)

Synchronous, and it creates AND immediately plays the source — don't call play() on it. The voice is SoLoud's own built-in formant synth: deliberately retro/robotic, not the platform's system TTS (no flutter_tts-style voice/rate/pitch controls, no per-platform quality differences).

Note bank helper

static Future<List<AudioSource>> SoLoudTools.createNotes({
  int octave = 3,               // asserted 0..4
  WaveForm waveForm = WaveForm.sin,
  bool superwave = true,
})

Returns 12 AudioSources (the chromatic notes starting at 55 Hz * 2^octave) ready to play(). Each is a separate source — dispose all 12 when done. Typical keyboard pattern:

final notes = await SoLoudTools.createNotes(octave: 2);
SoLoud.instance.play(notes[4]);                       // key pressed
await SoLoud.instance.stop(notes[4].handles.first);   // key released

Recipe: tone generator / instrument

Model on example/lib/waveform/waveform.dart:

1. await SoLoud.instance.init() once; SoLoud.instance.deinit() in the owning widget's dispose().
2. Create the source with loadWaveform, then play() it and keep both AudioSource and SoundHandle in state.
3. Wire UI controls straight to setWaveform* on the source while it plays.
4. On stop: await SoLoud.instance.stop(handle), and dispose the source when it's no longer needed (await SoLoud.instance.disposeSource(source)).

Traps

• play() is synchronous and returns SoundHandle — no await, and unlike just_audio there is no setUrl/AudioPlayer object; the SoLoud singleton is the whole player.
• Every synthesis call requires init() first and throws SoLoudNotInitializedException otherwise. init() is async; isInitialized lets you check synchronously.
• Waveform/speech sources are AudioSources like file-based ones. They are NOT auto-freed when playback ends: call disposeSource(source) (or disposeAllSources()), or let deinit() clean everything up. Creating a new loadWaveform per beep without disposing leaks.
• speechText() plays immediately. Calling play() on its returned source is wrong. Dispose it like any other source when finished (see example/tests/tests/speech_text.dart).
• setWaveformScale/setWaveformDetune are no-ops in practice unless super wave is on (loadWaveform(..., superWave: true, ...) or setWaveformSuperWave(sound, true)). The docs' own demo disables those sliders when super wave is off.
• setWaveform* targets the source, not a handle — it retunes all currently playing instances of that source. For per-note pitch, create one source per note (SoLoudTools.createNotes) instead of retuning one shared source.
• createNotes asserts octave in 0..4 and each call creates 12 sources — dispose them all, and don't call it repeatedly per key press; build the bank once.
• No envelopes/ADSR built in. Raw oscillators drone until stopped. Fade or stop handles yourself (stop(handle), or fadeVolume(handle, 0, duration) then stop) to avoid clicks and endless tones.
• Square/saw are loud and harsh — consider lowering play(..., volume: ...) or using the fSquare/fSaw filtered variants for smoother output.

More depth

• Demo: example/lib/waveform/waveform.dart — full tone generator UI (superWave/scale/detune sliders, all 9 WaveForm buttons).
• Tests with idiomatic usage: example/tests/tests/create_notes.dart, example/tests/tests/speech_text.dart, example/tests/tests/waveform_controls.dart.
• Real signatures: loadWaveform/setWaveform*/speechText at lib/src/soloud.dart:2076-2195; WaveForm at lib/src/enums.dart:290-317; SoLoudTools.createNotes in lib/src/tools/soloud_tools.dart.

Keeping this skill current

This skill ships inside the flutter_soloud package, so upgrading flutter_soloud can carry a newer revision of it than the copy installed in the project. To check, run:

dart run flutter_soloud:skills --check

It reports the installed and bundled skill versions and exits non-zero when an update is available. Offer to update with dart run flutter_soloud:skills (which touches only the skills, never pubspec or build files).