Audio Pipeline¶

Audio capture, ring buffer, and processing.

Data Flow¶

Microphone (Oboe / AVAudioEngine)
  → Uint8List (PCM16 little-endian, 32 kHz mono)
  → pcm16ToFloat32 (normalized −1.0 … 1.0)
  → RingBuffer.write
  → downstream consumers (spectrogram, inference, recording)

Ring Buffer¶

RingBuffer is a fixed-size circular buffer of Float32List samples. Multiple consumers can read from it simultaneously:

Spectrogram: reads the latest fftSize samples each frame
Inference: reads windowDuration * sampleRate samples each cycle
Recording: periodically flushes new samples to a WAV file

Audio Capture Service¶

AudioCaptureService wraps the platform microphone and pushes PCM16 data to the ring buffer. It also provides an RMS level stream (~15 Hz) for UI metering.

Recording Service¶

RecordingService supports two modes:

Full: Continuously flush the ring buffer to an audio file (WAV or FLAC depending on user settings) at 1-second intervals via AudioFileWriter (implemented by WavWriter and FlacEncoder).
Detections Only: Save audio clips centered on detection timestamps (pre-context + inference window + post-context) in the chosen format (WAV or FLAC).

On iOS, voice memos automatically fall back to .wav (PCM16) format to prevent Apple CoreAudio AAC compression collisions while maintaining full file-sharing and packaging compatibility.