feat: AutoGain filter

[alnitak]

Description

New autoGain filter for #7

• The loopback.dart example uses flutter_soloud to play audio back to the device from the microphone data stream. Please try it with a headset to prevent audio feedback.
• I do not have much experience in testing filter efficiency. To start please read the filter doc to know parameters meanings.
• No web support yet. Web supported.
• The Echo Cancellation feat: Echo Cancellation #5 code is not yet ready and I don't know if it will be!

Breaking change:

• the init method is now async
• FilterType renamed to RecorderFilterType
• an additional script must be added for the web platform. Now it looks like:

  <script src="assets/packages/flutter_recorder/web/libflutter_recorder_plugin.js" defer></script>
  <script src="assets/packages/flutter_recorder/web/init_recorder_module.dart.js" defer></script>
  

Closes #14

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

[CillianMyles]

@alnitak thanks for the web support, I'm looking into it. I have added you plugin to internal builds and I hope to have some feedback for you next week! 👍

[CillianMyles]

I got an exception on web checking if a device was initialised:

TypeError: Cannot read properties of undefined (reading '_isInited')
packages/flutter_recorder/src/bindings/recorder_web.dart 178:38                              isDeviceInitialized
packages/flutter_recorder/src/flutter_recorder.dart 239:38                                   isDeviceInitialized

These checks work fine on IO platforms. Here is the code for ref:

  void _initRecordingDevice() {
    if (!_flutterRecorder.isDeviceInitialized()) {
      _flutterRecorder.init(
        format: PCMFormat.s16le,
        sampleRate: 16000,
        channels: RecorderChannels.mono,
      );
    }
    _startRecordingDevice();
  }

  void _startRecordingDevice() {
    if (!_flutterRecorder.isDeviceStarted()) {
      _flutterRecorder.start();
    }
    if (!_flutterRecorder.filters.autoGainFilter.isActive) {
      _flutterRecorder.filters.autoGainFilter.activate();
    }
  }

  void _stopRecordingDevice() {
    if (_flutterRecorder.filters.autoGainFilter.isActive) {
      _flutterRecorder.filters.autoGainFilter.deactivate();
    }
    if (_flutterRecorder.isDeviceStarted()) {
      _flutterRecorder.stop();
    }
  }

  void _disposeRecordingDevice() {
    _stopRecordingDevice();
    if (_flutterRecorder.isDeviceInitialized()) {
      _flutterRecorder.deinit();
    }
  }

[alnitak]

Thanks @CillianMyles, I forgot some checks!

FYI now the init doesn't throw when already initialized. It just displays a log message. Ie the if (!_flutterRecorder.isDeviceStarted()) is no more needed.

Also, the logs are managed by package:logging, so you can initialize it like this:

import 'dart:developer' as dev;
import 'package:logging/logging.dart';

void main() async {
  // The `flutter_recorder` package logs everything
  // (from severe warnings to fine debug messages)
  // using the standard `package:logging`.
  // You can listen to the logs as shown below.
  Logger.root.level = kDebugMode ? Level.FINE : Level.INFO;
  Logger.root.onRecord.listen((record) {
    dev.log(
      record.message,
      time: record.time,
      level: record.level.value,
      name: record.loggerName,
      zone: record.zone,
      error: record.error,
      stackTrace: record.stackTrace,
    );
  });

  runApp(MyApp());
}

[CillianMyles]

Great news about the logging 🎉

---

I am now running into a number of other errors:

TypeError: Cannot read properties of undefined (reading '_isFilterActive')
packages/flutter_recorder/src/bindings/recorder_web.dart 290:12                              isFilterActive
packages/flutter_recorder/src/flutter_recorder.dart 429:28                                   isFilterActive

NoSuchMethodError: tried to call a non-function, such as null: 'dart.global.RecorderModule'
packages/flutter_recorder/src/bindings/js_extension.dart 21:21

TypeError: Cannot read properties of undefined (reading '_malloc')
packages/flutter_recorder/src/bindings/recorder_web.dart 113:22                 listCaptureDevices
packages/flutter_recorder/src/flutter_recorder.dart 188:33                      listCaptureDevices

[alnitak]

I am now running into a number of other errors:

I see. After changing the WASM module it must be initialized asynchronously somewhere. I chose to initialize it in the init method, so some other method calls don't work if the init has not yet been called.

I have to think about moving that initialization somewhere else! I'll update you

[alnitak]

The only safe way I found to initialize the WASM module is to do it in a JS script! So it should be added in the index.html alongside the recorder JS:

<script src="assets/packages/flutter_recorder/web/libflutter_recorder_plugin.js" defer></script>
<script src="assets/packages/flutter_recorder/web/init_recorder_module.dart.js" defer></script>

Two little breaking changes have been added also:

• the init method is now async
• FilterType renamed to RecorderFilterType

Hope it's all fine now and you can try the autogain also on the web and thanks for your patience!

[CillianMyles]

Thanks for the continued fixes 🙏

Latest:

TypeError: Cannot read properties of undefined (reading '_createWorkerInWasm')
packages/flutter_recorder/src/bindings/recorder_web.dart 41:5

Which is happening during init()

[alnitak]

Ouch! That should not happen after adding init_recorder_module.dart.js in the index.html. That .js should expose all the methods, _createWorkerInWasm included!

With Firefox and Chrome, it doesn't happen to me. Maybe moving those <script> in the <head> instead of the <body> tag?

[CillianMyles]

Hey @alnitak 👋

Happy new year 🎉

Apologies for the delay in getting back to you here.

The automatic gain seems to be working well. I will come back to you if I find any issues.

Thanks you for the great work 🙏

[alnitak]

I'm glad it worked, thanks for letting me know and happy new year to you too!