Flutter Recorder Recording

flutter_recorder file recording

flutter_recorder can record captured microphone audio directly into WAV (uncompressed PCM) or Ogg Opus (compressed, high quality, low bitrate) audio files. Recording supports live pause and resume without breaking or splitting the output file.

Minimal example

import 'dart:io';
import 'package:flutter/foundation.dart';
import 'package:flutter_recorder/flutter_recorder.dart';
import 'package:path_provider/path_provider.dart';

Future<void> recordAudio() async {
  final recorder = Recorder.instance;

  // 1. Initialize and start the capture engine
  await recorder.init(
    format: PCMFormat.f32le,
    sampleRate: 44100,
    channels: RecorderChannels.mono,
  );
  recorder.start();

  // 2. Determine target path (Desktop/Mobile vs Web)
  String filePath = '';
  if (!kIsWeb) {
    final dir = await getApplicationDocumentsDirectory();
    filePath = '${dir.path}/my_recording.wav';
  }

  // 3. Start recording to file (WAV default)
  recorder.startRecording(
    completeFilePath: filePath,
    format: RecordingFormat.wav,
  );

  // 4. Optional: Pause and resume recording
  recorder.setPauseRecording(pause: true);
  // ... silence or user paused ...
  recorder.setPauseRecording(pause: false);

  // 5. Stop recording and finalize file header
  recorder.stopRecording();

  // 6. Stop and deinit capture
  recorder.stop();
  recorder.deinit();
}

Formats: WAV vs Ogg Opus

Select the output format via the format parameter in startRecording:

// Uncompressed WAV
recorder.startRecording(
  completeFilePath: '/path/to/recording.wav',
  format: RecordingFormat.wav,
);

// High-efficiency Ogg Opus
recorder.startRecording(
  completeFilePath: '/path/to/recording.opus',
  format: RecordingFormat.opusOgg,
);

The API Shape

All recording methods are called on Recorder.instance:

• void startRecording({String completeFilePath = '', RecordingFormat format = RecordingFormat.wav}): Starts writing captured audio into the specified file.
  • On non-web platforms, completeFilePath is mandatory.
  • On Web, completeFilePath is ignored; audio is held in memory and downloaded upon stopping.
  • Throws RecorderNotInitializedException if init() was not called.
  • Throws RecorderCaptureNotStartededException if start() was not called.
  • Throws RecorderInvalidFileNameException if the destination path is invalid.
• void setPauseRecording({required bool pause}): Pauses (pause: true) or unpauses (pause: false) writing into the recording file without interrupting the microphone capture stream.
• void stopRecording(): Finalizes the audio file, writes header metadata (such as WAV riff size and sample counts), closes the file descriptor, and flushes to disk.

Cross-Platform File Paths

Use package:path_provider to ensure safe, writable directories:

import 'dart:io';
import 'package:flutter/foundation.dart';
import 'package:path_provider/path_provider.dart';

Future<String> getRecordingPath({String fileName = 'recording.wav'}) async {
  if (kIsWeb) return ''; // Ignored on Web

  final Directory saveDir;
  if (defaultTargetPlatform == TargetPlatform.iOS ||
      defaultTargetPlatform == TargetPlatform.android) {
    // Mobile: Sandboxed documents directory
    saveDir = await getApplicationDocumentsDirectory();
  } else {
    // Desktop (macOS, Windows, Linux): Downloads or Application Documents
    final downloads = await getDownloadsDirectory();
    saveDir = downloads ?? await getApplicationDocumentsDirectory();
  }

  if (!saveDir.existsSync()) {
    saveDir.createSync(recursive: true);
  }
  return '${saveDir.path}/$fileName';
}

Silence Detection Pre-Roll Buffering

When recording with silence detection enabled, you can write audio that occurred immediately before voice triggered recording, ensuring words are never clipped at the start of a sentence:

// Retain 0.5 seconds of audio prior to speech detection
Recorder.instance.setSecondsOfAudioToWriteBefore(0.5);

Traps & Gotchas

• start() must be called before startRecording(): Calling startRecording() when isStarted is false throws RecorderCaptureNotStartededException.
• completeFilePath is required on mobile and desktop: Omitting or passing an empty string on non-web platforms causes an assertion failure or RecorderInvalidFileNameException.
• Always call stopRecording() before stop() / deinit(): Stopping the engine without stopping the recording may leave the file header incomplete or corrupt.
• On Web, stopRecording() triggers a browser download: No local file system path is used on the web.
• File Overwrites: If completeFilePath points to an existing file, the recorder will overwrite it. Clean up existing files if you want to verify new creation.

Keeping this skill current

This skill ships inside the flutter_recorder package. To check for updates, run:

dart run flutter_recorder:skills --check