Audio Streaming

flutter_soloud supports streaming audio data while receiving it in real-time. The supported audio data formats are raw PCM, MP3, WAV, or compressed through the Opus, Vorbis, and FLAC codecs with Ogg container libraries from Xiph.org. This is particularly useful when:

• Streaming audio from network sources like icecast radio
• Working with OpenAI or other streaming APIs
• Generating audio data on-the-fly
• Processing audio in chunks
• Automatically pause when buffering is needed and resume playback when enough data is available

The Opus and Ogg libraries are embedded by default in flutter_soloud. However, if you don't need streaming capabilities, please read the No Xiph libs section for how to exclude these libraries from your app.

The package provides two groups of streaming APIs:

• Push buffers — the classic setBufferStream API described on this page. You push audio data with addAudioDataStream and the engine manages playback.
• Pull buffers — the newer setPullBufferStream API described in Pull Buffer Streaming. The engine asks for data on demand via a callback, which is especially useful for large files, network streaming, and encrypted sources.

Push buffers use setBufferStream and support two buffering modes:

• BufferingType.preserved — keeps all audio data in memory, supports seeking and looping, but uses more RAM.
• BufferingType.released — frees played audio data, lower memory usage, single playback instance only, and getPosition always returns 0.

Initialize an audio stream:

final stream = SoLoud.instance.setBufferStream(
  maxBufferSizeBytes: 1024 * 1024 * 10,   // 10MB of max buffer (not allocated)
  bufferingType: BufferingType.preserved, // Keep all data in memory
  bufferingTimeNeeds: 2.0,                // 2 seconds to buffer before unpausing
  sampleRate: 44100,                      // 44100 Hz
  channels: Channels.stereo,              // 2 channels
  format: BufferType.auto,                // Autodetect format (not valid for raw PCM)
  onBuffering: (isBuffering, handle, time) {
    // Handle buffering
  },
  onMetadata: (metadata) {
    // Handle metadata
  },
);

Parameters:

final stream = await SoLoud.instance.setBufferStream(
  bufferingType: BufferingType.preserved,
  // ...other parameters
);

• Keeps all audio data in memory
• Allows multiple playback instances
• Supports seeking and looping
• Higher memory usage

final stream = await SoLoud.instance.setBufferStream(
  bufferingType: BufferingType.released,
  // ...other parameters
);

• Frees played audio data
• The position of the stream is always 0
• The seek method is not supported
• Single playback instance only
• Lower memory usage
• Must be manually disposed

WARNING: as you can see, the position of the stream in released mode is always at start. This means that getPosition always returns 0. To get the already played time, you should use the getStreamTimeConsumed method instead (basically it is the current position). Also, seek is not supported in released mode.

Please, look at the example/lib/buffer_stream/simple_noise_stream.dart example for a simple implementation to understand how audio stream works.

For raw PCM data, the following formats are supported:

• s8 - Signed 8-bit PCM
• s16le - Signed 16-bit PCM (little endian)
• s32le - Signed 32-bit PCM (little endian)
• f32le - 32-bit float PCM (little endian)

You should also need to specify the sample rate and the number of channels.

• auto - Automatically detect the format

Supported formats are:

• mp3 - Mp3 format
• wav - Wav format
• flac - FLAC format
• opus - Ogg container with Opus codec
• ogg - Ogg container with Vorbis codec
• flac - Ogg container with FLAC codec These compressed formats support metadata (using the onMetadata callback).

// Add audio data to the stream
SoLoud.instance.addAudioDataStream(
  stream,
  audioChunk,  // Uint8List of audio data
);

// Mark the stream as complete
SoLoud.instance.setDataIsEnded(stream);

// Get current buffer size in bytes
final size = SoLoud.instance.getBufferSize(stream);

// Reset the buffer
SoLoud.instance.resetBufferStream(stream);

// Create a WebSocket connection
final socket =
    await WebSocket.connect('wss://audio-stream.example.com');

// Set up the audio stream
final stream = SoLoud.instance.setBufferStream(
  bufferingType: BufferingType.released,
  format: BufferType.opus,
  onBuffering: (isBuffering, handle, time) {
    // When isBuffering==true, the stream is set to paused automatically till
    // it reaches bufferingTimeNeeds of audio data or until setDataIsEnded is called
    // or maxBufferSizeBytes is reached. When isBuffering==false, the playback stream
    // is resumed.
    print('Buffering: $isBuffering, Time: $time');
  },
  onMetadata: (metadata) {
    debugPrint(metadata.toString());
  },
  }
);

// Start the the playback whenever enough data is buffered (defined by `bufferingTimeNeeds` seconds) whenever enough data is buffered (defined by `bufferingTimeNeeds` seconds)
final handle = await SoLoud.instance.play(stream);

// Eventually listen for the handle to finish playing.
// `SoLoud.setDataIsEnded` must be called before this listener
// could be emitted.
stream.soundEvents.listen((event) {
  if (event.event == SoundEventType.handleIsNoMoreValid &&
      event.handle == handle) {
    print('sound has finished playing');
  }
});

// Listen for audio data
socket.listen(
  (data) {
    if (data is List<int>) {
      SoLoud.instance.addAudioDataStream(
        stream,
        Uint8List.fromList(data),
      );
    }
  },
  onDone: () {
    // Mark the stream as completed.
    // You can then listen to the `stream.soundEvents` events
    SoLoud.instance.setDataIsEnded(stream);
  },
);

Please, look at the example/lib/buffer_stream/web_radio.dart example for a simple implementation to connect to an online icecast web radio or at example/lib/buffer_stream/websocket.dart example to connect to a WebSocket server (please read the note at the beginning).

@pragma('vm:entry-point')
Future<AudioSource> generatePCM() async {
  final pcmStream = SoLoud.instance.setBufferStream(
    maxBufferSizeBytes: 1024 * 1024,
    format: BufferType.s16le,
    channels: Channels.mono,
    sampleRate: 44100,
  );
  
  // Generate some PCM data
  final buffer = Int16List(44100);
  for (var i = 0; i &lt; buffer.length; i++) {
    buffer[i] = (sin(2 * pi * 440 * i / 44100) * 32767).toInt();
  }
  
  // Add to stream
  SoLoud.instance.addAudioDataStream(
    pcmStream,
    buffer.buffer.asUint8List(),
  );
  
  SoLoud.instance.setDataIsEnded(pcmStream);
  return pcmStream;
}

• Choose BufferingType.released for long streams and continuous network feeds.
• Use BufferingType.preserved when you need seeking, looping, or multiple playback instances of the same stream.
• For very large files (many GB) where you cannot hold the whole stream in memory, consider using the pull buffer API described in Pull Buffer Streaming. It decodes a fixed-size circular window on demand and does not require the full audio data to be available in memory or pushed ahead of time.
• Consider memory usage when streaming large files.
• Handle network errors and buffering states.
• Clean up streams when no longer needed.

For scenarios where the audio source is too large to hold in memory, is delivered on demand, or requires custom fetching logic, flutter_soloud also offers a pull buffer streaming API. With pull buffers:

• The engine requests encoded data via onMoreDataIsNeeded whenever the decoded circular buffer drops below a configurable threshold.
• You supply the data from any source: local files, network ranges, decryption layers, or custom protocols.
• The plugin maintains only a fixed decoded circular buffer, so memory usage is bounded regardless of the total audio size.

This is ideal for long podcasts, music libraries, or remote files where you want to stream incrementally without loading everything into RAM. The trade-off is that pull buffers require the total audio size (audioSizeBytes) in advance for accurate duration calculation and tail handling, and the source must be fetchable by byte offset.