Initial steps towards microphone HAL

Audio format needs some investigation - MediaRecorder might not be the
right approach.

src/board/audio/index.ts

@@ -66,46 +66,6 @@ export class BoardAudio {
     );
   }
 
-  async record() {
-      let mediaRecorder: MediaRecorder | undefined;
-      if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
-        try {
-          const stream = await navigator.mediaDevices.getUserMedia({ video: false, audio: true });
-          mediaRecorder = new MediaRecorder(stream);
-          mediaRecorder.start();
-
-          setTimeout(() => {
-            if (mediaRecorder) {
-              mediaRecorder.stop();
-            }
-          }, 5000)
-
-          const chunks:Blob[] = []
-          mediaRecorder.ondataavailable = (e: BlobEvent) => {
-            chunks.push(e.data);
-          }
-
-          mediaRecorder.onstop = async () => {
-            if (chunks.length > 0) {
-                const recordingType = 'audio/wav; codecs=MS_PCM' 
-                const blob = new Blob(chunks, { type: recordingType });
-                const audioURL = window.URL.createObjectURL(blob);
-                const recording = new Audio(audioURL);
-                await recording.play()
-            }
-          }
-
-        } catch (error) {
-            console.log("An error occurred, could not get microphone access");
-            if (mediaRecorder) {
-                mediaRecorder.stop();
-            }
-        }
-    } else {
-        console.log("getUserMedia not supported on your browser!");
-    }
-  }
-
   async createAudioContextFromUserInteraction(): Promise<void> {
     this.context =
       this.context ??

src/board/index.ts

@@ -513,10 +513,6 @@ export class Board {
     return this.runningPromise;
   }
 
-  async record(): Promise<void> {
-    await this.audio.record()
-  }
-
   /**
    * An external reset.
    */
@@ -786,10 +782,6 @@ export const createMessageListener = (board: Board) => (e: MessageEvent) => {
         board.stop();
         break;
       }
-      case "record": {
-        board.record();
-        break;
-      }
       case "reset": {
         board.reset();
         break;

src/board/microphone.ts

@@ -17,6 +17,7 @@ export class Microphone {
     150
   );
   private soundLevelCallback: SoundLevelCallback | undefined;
+  private _isRecording: boolean = false;
 
   constructor(
     private element: SVGElement,
@@ -66,4 +67,54 @@ export class Microphone {
   boardStopped() {
     this.microphoneOff();
   }
+
+  isRecording() {
+    return this._isRecording;
+  }
+
+  stopRecording() {
+    // TODO
+  }
+
+  async startRecording(onChunk: (chunk: ArrayBuffer) => void) {
+    if (!navigator?.mediaDevices?.getUserMedia) {
+      return;
+    }
+    if (this.isRecording()) {
+      this.stopRecording();
+      // Wait for it if needed
+    }
+    this._isRecording = true;
+
+    // This might not be the right recording approach as we want 8 bit PCM for AudioFrame
+    // and we're getting a fancy codec.
+    let mediaRecorder: MediaRecorder | undefined;
+    try {
+      const stream = await navigator.mediaDevices.getUserMedia({
+        video: false,
+        audio: true,
+      });
+      mediaRecorder = new MediaRecorder(stream);
+      mediaRecorder.start();
+
+      setTimeout(() => {
+        if (mediaRecorder) {
+          mediaRecorder.stop();
+        }
+      }, 5000);
+
+      mediaRecorder.ondataavailable = async (e: BlobEvent) => {
+        const buffer = await e.data.arrayBuffer();
+        onChunk(buffer);
+      };
+      mediaRecorder.onstop = async () => {
+        this._isRecording = false;
+      };
+    } catch (error) {
+      if (mediaRecorder) {
+        mediaRecorder.stop();
+      }
+      this._isRecording = false;
+    }
+  }
 }

src/demo.html

@@ -115,7 +115,6 @@ <h1>MicroPython-micro:bit simulator example embedding</h1>
             <div class="actions">
               <button id="stop">Stop</button>
               <button id="reset">Reset</button>
-              <button id="record">Record</button>
               <button id="mute">Mute</button>
               <button id="unmute">Unmute</button>
             </div>
@@ -242,15 +241,6 @@ <h1>MicroPython-micro:bit simulator example embedding</h1>
         );
       });
 
-      document.querySelector("#record").addEventListener("click", async () => {
-        simulator.postMessage(
-          {
-            kind: "record",
-          },
-          "*"
-        );
-      });
-
       document.querySelector("#reset").addEventListener("click", async () => {
         simulator.postMessage(
           {

src/jshal.h

@@ -85,6 +85,9 @@ bool mp_js_hal_audio_is_expression_active(void);
 void mp_js_hal_microphone_init(void);
 void mp_js_hal_microphone_set_threshold(int kind, int value);
 int mp_js_hal_microphone_get_level(void);
+void mp_js_hal_microphone_start_recording(uint8_t *buf, size_t max_len, size_t *cur_len, int rate);
+bool mp_js_hal_microphone_is_recording(void);
+void mp_js_hal_microphone_stop_recording(void);
 
 void mp_js_radio_enable(uint8_t group, uint8_t max_payload, uint8_t queue);
 void mp_js_radio_disable(void);

src/jshal.js

@@ -287,6 +287,25 @@ mergeInto(LibraryManager.library, {
     );
   },
 
+  mp_js_hal_microphone_start_recording: function (
+    /** @type {number} */ buf,
+    /** @type {number} */ max_len,
+    /** @type {number} */ cur_len,
+    /** @type {number} */ rate
+  ) {
+    Module.board.microphone.startRecording(function (
+      chunk
+    ) /** @type {ArrayBuffer} */
+    {
+      console.log("Chunk", chunk);
+    });
+  },
+  mp_js_hal_microphone_is_recording: function () {
+    return Module.board.microphone.isRecording();
+  },
+  mp_js_hal_microphone_stop_recording: function () {
+    Module.board.microphone.stopRecording();
+  },
   mp_js_hal_microphone_get_level: function () {
     return Module.board.microphone.soundLevel.value;
   },

src/microbithal_js.c

@@ -514,11 +514,13 @@ int microbit_hal_microphone_get_level(void) {
 }
 
 void microbit_hal_microphone_start_recording(uint8_t *buf, size_t max_len, size_t *cur_len, int rate) {
+    mp_js_hal_microphone_start_recording(buf, max_len, cur_len, rate);
 }
 
 bool microbit_hal_microphone_is_recording(void) {
-    return false;
+    return mp_js_hal_microphone_is_recording();
 }
 
 void microbit_hal_microphone_stop_recording(void) {
+    mp_js_hal_microphone_stop_recording();
 }