audio_stream_player 1.0.2

Low-latency PCM audio streaming player. Feed raw audio chunks from TTS or realtime voice APIs and hear them as they arrive, with buffer introspection and underrun events.

audio_stream_player

A low-latency raw PCM streaming player for Flutter. Feed audio byte chunks from a TTS or realtime voice API and hear them as they arrive — no files, no URLs, no waiting for the full response.

final player = await AudioStreamPlayer.create(sampleRate: 24000);
await player.play();

await for (final chunk in ttsApi.streamAudio(text)) {
  await player.feed(chunk); // Uint8List of s16le PCM
}

await player.endOfStream(); // completes when the last sample has played

Why this package

General-purpose players (just_audio, audioplayers) are built around URLs and files; wiring a live byte stream into them is awkward. flutter_pcm_sound and flutter_sound can play PCM streams — the former through a feed-me callback (s16 only, one global player), the latter as part of a full recorder/player suite. This package does one thing: gapless playback of PCM chunks as they arrive, with the lifecycle hooks a streaming voice app actually needs:

• Any stream rate — feed 22.05/24/44.1 kHz mono straight from the API; resampling to the hardware rate is native.
• Chunk-boundary safe — chunks can split a sample frame anywhere; the remainder is carried automatically.
• endOfStream() future — know exactly when the utterance finished playing (for "speaking" indicators, turn-taking, barge-in).
• Underrun events + buffered duration — show buffering UI, tune your chunk delivery, or implement backpressure.
• Pause / resume / stop-and-flush — interrupt an utterance cleanly.
• Multiple concurrent players — TTS voice and sound effects side by side.

Platform	Backend	Minimum
Android	AudioTrack (low-latency mode)	API 21
iOS	AVAudioEngine	13.0
macOS	AVAudioEngine	10.15

Usage

Create a player

final player = await AudioStreamPlayer.create(
  sampleRate: 24000,          // rate of the bytes you feed
  channels: 1,                // 1 or 2, interleaved
  format: PcmFormat.s16le,    // or PcmFormat.f32le
);

On iOS the audio session is configured for playback automatically. If you manage the session yourself (e.g. with audio_session), pass configureAudioSession: false.

Stream an utterance

await player.play();                  // safe before any data arrives
await for (final chunk in source) {
  await player.feed(chunk);
}
await player.endOfStream();           // resolves after the last sample plays

After the drain the player returns to PlayerState.idle and can be fed the next utterance.

Observe playback

player.onStateChanged.listen((s) => ...);   // idle / playing / paused
player.onUnderrun.listen((_) => ...);       // buffer starved mid-stream
final buffered = await player.bufferedDuration();

An underrun is not an error — playback resumes by itself when the next chunk arrives. Use it to decide whether to delay play() until you have some audio buffered.

Interrupt

await player.pause();  // keeps buffered audio, resume with play()
await player.stop();   // discards buffered audio, back to idle

stop() is the barge-in primitive: call it when the user starts talking over the assistant.

Clean up

await player.dispose();

Notes

• Buffering is unbounded: if your source can outrun playback for minutes, poll bufferedDuration() and throttle your reads.
• Bytes are interleaved little-endian PCM, the wire format of essentially every TTS API. PcmFormat.s16le matches OpenAI, ElevenLabs, Cartesia, Google, and Amazon defaults.
• The example app simulates a jittery TTS byte stream end-to-end, including underrun recovery — cd example && flutter run.