Merge pull request #689 from cph-cachet/audiostreamer-dev

Audiostreamer dev: custom sample rate

Author: hoffmatteo

packages/audio_streamer/CHANGELOG.md

@@ -1,41 +1,59 @@
+## 2.3.0
+
+- implemented custom sample rate functionality
+- [PR#521](https://github.com/cph-cachet/flutter-plugins/pull/521)
+- [PR#522](https://github.com/cph-cachet/flutter-plugins/pull/522)
+
 ## 2.2.0+1
+
 - updated example app podfile to correctly include permission for iOS
 - updated README to include podfile permission
 
 ## 2.2.0
+
 - upgrade of `permission_handler: ^10.0.0`
 - Upgraded to Dart 2.17 and Flutter 3.0
 
 ## 2.1.0
+
 - upgrade of `permission_handler: ^9.2.0`
 - [PR#503](https://github.com/cph-cachet/flutter-plugins/pull/503)
 - [PR#504](https://github.com/cph-cachet/flutter-plugins/pull/504)
 
 ## 2.0.3
+
 - [PR#371](https://github.com/cph-cachet/flutter-plugins/pull/371)
 
 ## 2.0.2
+
 - [PR#364](https://github.com/cph-cachet/flutter-plugins/pull/364)
 - upgrade to `permission_handler: ^8.1.0`
- 
+
 ## 2.0.0
+
 - Null safety migration
 
 ## 1.3.0
+
 - Fixed an issue where using another media player/recorder would cause the plugin to go into an error state on iOS (see https://github.com/cph-cachet/flutter-plugins/issues/86)
 
 ## 1.2.0
+
 - Fixed an issue where the AVAudioRecorder would crash on iOS (see https://github.com/cph-cachet/flutter-plugins/issues/91)
 
 ## 1.1.6
+
 - Upgrade to `permission_handler` v. 5.
 
 ## 1.1.5
+
 - Added a getter for the sample rate field.
 
 ## 1.1.0
+
 - Able to stream audio data on Android as well
 - The plugin will now record as soon as the permission dialog ends.
 
 ## 1.0.0
+
 - Able to stream audio data on iOS.

packages/audio_streamer/README.md

@@ -1,8 +1,9 @@
 # Audio Streamer
 
-Streaming of PCM audio from Android and iOS with a sample rate of 44,100 Hz
+Streaming of PCM audio from Android and iOS with a customizable sample rate.
 
 ## Permissions
+
 On **Android** add the audio recording permission to `AndroidManifest.xml`:
 
 ```xml
@@ -11,8 +12,8 @@ On **Android** add the audio recording permission to `AndroidManifest.xml`:
 
 On **iOS** enable the following:
 
-* Capabilities > Background Modes > _Audio, AirPlay and Picture in Picture_
-* In the Runner Xcode project edit the `Info.plist` file. Add an entry for _'Privacy - Microphone Usage Description'_
+- Capabilities > Background Modes > _Audio, AirPlay and Picture in Picture_
+- In the Runner Xcode project edit the `Info.plist` file. Add an entry for _'Privacy - Microphone Usage Description'_
 
 When editing the `Info.plist` file manually, the entries needed are:
 
@@ -25,7 +26,7 @@ When editing the `Info.plist` file manually, the entries needed are:
 </array>
 ```
 
-* Edit the `Podfile` to include the permission for the microphone:
+- Edit the `Podfile` to include the permission for the microphone:
 
 ```ruby
 post_install do |installer|
@@ -43,13 +44,15 @@ end
 ```
 
 ## Example
+
 See the file `example/lib/main.dart` for a fully fledged example app using the plugin.
+Note that on iOS the sample rate will not necessarily change, as there is only the option to set a preferred one.
 
 ```dart
   AudioStreamer _streamer = AudioStreamer();
   bool _isRecording = false;
   List<double> _audio = [];
-  
+
   void onAudio(List<double> buffer) {
     _audio.addAll(buffer);
     double secondsRecorded = _audio.length.toDouble() / _streamer.sampleRate.toDouble();
@@ -58,7 +61,8 @@ See the file `example/lib/main.dart` for a fully fledged example app using the p
 
   void start() async {
     try {
-      _streamer.start(onAudio);
+      //_streamer.start(onAudio, handleError, sampleRate: 16000); //uses custom sample rate
+      _streamer.start(onAudio, handleError); //uses default sample rate of 44100 Hz
       setState(() {
         _isRecording = true;
       });

packages/audio_streamer/android/src/main/kotlin/plugins/cachet/audio_streamer/AudioStreamerPlugin.kt

@@ -15,29 +15,45 @@ import io.flutter.embedding.engine.plugins.activity.ActivityAware
 import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding
 import io.flutter.plugin.common.EventChannel
 import io.flutter.plugin.common.EventChannel.EventSink
+import io.flutter.plugin.common.MethodChannel
 import io.flutter.plugin.common.PluginRegistry.RequestPermissionsResultListener
 import java.util.*
 
 /** AudioStreamerPlugin */
 class AudioStreamerPlugin : FlutterPlugin, RequestPermissionsResultListener, EventChannel.StreamHandler, ActivityAware {
 
-    /// Constants
+    // / Constants
     private val eventChannelName = "audio_streamer.eventChannel"
-    private val sampleRate = 44100
-    private var bufferSize = 6400 * 2; /// Magical number!
+
+    // / Method channel for returning the sample rate.
+    private val methodChannelName = "audio_streamer.methodChannel"
+    private var sampleRate = 44100 // standard value to initialize
+    private var bufferSize = 6400 * 2; // / Magical number!
     private val maxAmplitude = 32767 // same as 2^15
     private val logTag = "AudioStreamerPlugin"
 
-    /// Variables (i.e. will change value)
+    // / Variables (i.e. will change value)
     private var eventSink: EventSink? = null
     private var recording = false
 
     private var currentActivity: Activity? = null
 
+    private lateinit var audioRecord: AudioRecord;
+
     override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
         val messenger = flutterPluginBinding.binaryMessenger
         val eventChannel = EventChannel(messenger, eventChannelName)
         eventChannel.setStreamHandler(this)
+        val methodChannel = MethodChannel(messenger, methodChannelName)
+        methodChannel.setMethodCallHandler {
+                call, result ->
+            if (call.method == "getSampleRate") {
+                // Sample rate never changes, so return the given sample rate.
+                result.success(audioRecord?.getSampleRate())
+            } else {
+                result.notImplemented()
+            }
+        }
     }
 
     override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) {
@@ -63,11 +79,16 @@ class AudioStreamerPlugin : FlutterPlugin, RequestPermissionsResultListener, Eve
     }
 
     /**
-     * Called from Flutter, starts the stream.
+     * Called from Flutter, starts the stream and updates the sample rate using the argument.
      */
     override fun onListen(arguments: Any?, events: EventSink?) {
         this.eventSink = events
         recording = true
+        sampleRate = (arguments as Map<*, *>)["sampleRate"] as Int
+        if (sampleRate < 4000 || sampleRate > 48000) {
+            events!!.error("SampleRateError", "A sample rate of " + sampleRate + "Hz is not supported by Android.", null)
+            return
+        }
         streamMicData()
     }
 
@@ -92,42 +113,45 @@ class AudioStreamerPlugin : FlutterPlugin, RequestPermissionsResultListener, Eve
     /**
      * Starts recording and streaming audio data from the mic.
      * Uses a buffer array of size 512. Whenever buffer is full, the content is sent to Flutter.
-     *
+     * Sets the sample rate as defined by [sampleRate].
      *
      * Source:
      * https://www.newventuresoftware.com/blog/record-play-and-visualize-raw-audio-data-in-android
      */
     private fun streamMicData() {
-        Thread(Runnable {
-            Process.setThreadPriority(Process.THREAD_PRIORITY_AUDIO)
-            val audioBuffer = ShortArray(bufferSize / 2)
-            val record = AudioRecord(
+        Thread(
+            Runnable {
+                Process.setThreadPriority(Process.THREAD_PRIORITY_AUDIO)
+                val audioBuffer = ShortArray(bufferSize / 2)
+                audioRecord = AudioRecord(
                     MediaRecorder.AudioSource.DEFAULT,
                     sampleRate,
                     AudioFormat.CHANNEL_IN_MONO,
                     AudioFormat.ENCODING_PCM_16BIT,
-                    bufferSize)
-            if (record.state != AudioRecord.STATE_INITIALIZED) {
-                Log.e(logTag, "Audio Record can't initialize!")
-                return@Runnable
-            }
-            /** Start recording loop  */
-            record.startRecording()
-            while (recording) {
-                /** Read data into buffer  */
-                record.read(audioBuffer, 0, audioBuffer.size)
-                Handler(Looper.getMainLooper()).post {
-                    /// Convert to list in order to send via EventChannel.
-                    val audioBufferList = ArrayList<Double>()
-                    for (impulse in audioBuffer) {
-                        val normalizedImpulse = impulse.toDouble() / maxAmplitude.toDouble()
-                        audioBufferList.add(normalizedImpulse)
+                    bufferSize,
+                )
+                if (audioRecord.state != AudioRecord.STATE_INITIALIZED) {
+                    Log.e(logTag, "Audio Record can't initialize!")
+                    return@Runnable
+                }
+                /** Start recording loop  */
+                audioRecord.startRecording()
+                while (recording) {
+                    /** Read data into buffer  */
+                    audioRecord.read(audioBuffer, 0, audioBuffer.size)
+                    Handler(Looper.getMainLooper()).post {
+                        // / Convert to list in order to send via EventChannel.
+                        val audioBufferList = ArrayList<Double>()
+                        for (impulse in audioBuffer) {
+                            val normalizedImpulse = impulse.toDouble() / maxAmplitude.toDouble()
+                            audioBufferList.add(normalizedImpulse)
+                        }
+                        eventSink!!.success(audioBufferList)
                     }
-                    eventSink!!.success(audioBufferList)
                 }
-            }
-            record.stop()
-            record.release()
-        }).start()
+                audioRecord.stop()
+                audioRecord.release()
+            },
+        ).start()
     }
 }

packages/audio_streamer/example/ios/Flutter/.last_build_id

@@ -23,10 +23,10 @@ class _MyAppState extends State<MyApp> {
     super.initState();
   }
 
-  void onAudio(List<double> buffer) {
+  void onAudio(List<double> buffer) async {
     _audio.addAll(buffer);
-    double secondsRecorded =
-        _audio.length.toDouble() / AudioStreamer.sampleRate.toDouble();
+    var sampleRate = await AudioStreamer.currSampleRate;
+    double secondsRecorded = _audio.length.toDouble() / sampleRate;
     print('Max amp: ${buffer.reduce(max)}');
     print('Min amp: ${buffer.reduce(min)}');
     print('$secondsRecorded seconds recorded.');
@@ -43,7 +43,9 @@ class _MyAppState extends State<MyApp> {
 
   void start() async {
     try {
-      _streamer.start(onAudio, handleError);
+      //_streamer.start(onAudio, handleError, sampleRate: 16000); //uses custom sample rate
+      _streamer.start(
+          onAudio, handleError); //uses default sample rate of 44100 Hz
       setState(() {
         _isRecording = true;
       });