get safari-friendly audioContext instance (#213)

* get safari-friendly audioContext instance wherever AudioContext is created, add playResultAudio method to BaseAudioPlayer

* Pull getAudioContext into less public class, use getSampleAudio with test for webkit

src/common.browser/MicAudioSource.ts

@@ -302,17 +302,7 @@ export class MicAudioSource implements IAudioSource {
             return;
         }
 
-        // https://developer.mozilla.org/en-US/docs/Web/API/AudioContext
-        if (typeof (AudioContext) === "undefined") {
-            throw new Error("Browser does not support Web Audio API (AudioContext is not available).");
-        }
-
-        // Browsers without sampleRate constraint support can't connect nodes with different sample rates
-        if (navigator.mediaDevices.getSupportedConstraints().sampleRate) {
-            this.privContext = new AudioContext({ sampleRate: MicAudioSource.AUDIOFORMAT.samplesPerSec });
-        } else {
-            this.privContext = new AudioContext();
-        }
+        this.privContext = AudioStreamFormatImpl.getAudioContext(MicAudioSource.AUDIOFORMAT.samplesPerSec);
     }
 
     private async destroyAudioContext(): Promise<void> {

src/sdk/Audio/AudioStreamFormat.ts

@@ -108,6 +108,31 @@ export class AudioStreamFormatImpl extends AudioStreamFormat {
         return new AudioStreamFormatImpl();
     }
 
+    /**
+     * Creates an audio context appropriate to current browser
+     * @member AudioStreamFormatImpl.getAudioContext
+     * @function
+     * @public
+     * @returns {AudioContext} An audio context instance
+     */
+    public static getAudioContext(sampleRate?: number): AudioContext {
+        // Workaround for Speech SDK bug in Safari.
+        const AudioContext = (window as any).AudioContext // our preferred impl
+            || (window as any).webkitAudioContext // fallback, mostly when on Safari
+            || false; // could not find.
+
+        // https://developer.mozilla.org/en-US/docs/Web/API/AudioContext
+        if (!!AudioContext) {
+            if (sampleRate !== undefined && navigator.mediaDevices.getSupportedConstraints().sampleRate) {
+                return new AudioContext({ sampleRate });
+            } else {
+                return new AudioContext();
+            }
+        } else {
+            throw new Error("Browser does not support Web Audio API (AudioContext is not available).");
+        }
+    }
+
     /**
      * Closes the configuration object.
      * @member AudioStreamFormatImpl.prototype.close

src/sdk/Audio/BaseAudioPlayer.ts

@@ -23,8 +23,12 @@ export class BaseAudioPlayer {
     /**
      * Creates and initializes an instance of this class.
      * @constructor
+     * @param {AudioStreamFormat} audioFormat audio stream format recognized by the player.
      */
-    public constructor(audioFormat: AudioStreamFormat) {
+    public constructor(audioFormat?: AudioStreamFormat) {
+        if (audioFormat === undefined) {
+            audioFormat = AudioStreamFormat.getDefaultInputFormat();
+        }
         this.init(audioFormat);
     }
 
@@ -33,13 +37,18 @@ export class BaseAudioPlayer {
      * @param newAudioData audio data to be played.
      */
     public playAudioSample(newAudioData: ArrayBuffer): void {
-        this.ensureInitializedContext();
-        const audioData = this.formatAudioData(newAudioData);
-        const newSamplesData = new Float32Array(this.samples.length + audioData.length);
-        newSamplesData.set(this.samples, 0);
-        newSamplesData.set(audioData, this.samples.length);
-        this.samples = newSamplesData;
+        if (!!(window as any).webkitAudioContext) {
+            this.playAudio(newAudioData);
+        } else {
+            this.ensureInitializedContext();
+            const audioData = this.formatAudioData(newAudioData);
+            const newSamplesData = new Float32Array(this.samples.length + audioData.length);
+            newSamplesData.set(this.samples, 0);
+            newSamplesData.set(audioData, this.samples.length);
+            this.samples = newSamplesData;
+        }
     }
+
     /**
      * stops audio and clears the buffers
      */
@@ -77,7 +86,7 @@ export class BaseAudioPlayer {
 
     private createAudioContext(): void {
         // new ((window as any).AudioContext || (window as any).webkitAudioContext)();
-        this.audioContext = new AudioContext();
+        this.audioContext = AudioStreamFormatImpl.getAudioContext();
 
         // TODO: Various examples shows this gain node, it does not seem to be needed unless we plan
         // to control the volume, not likely
@@ -142,4 +151,17 @@ export class BaseAudioPlayer {
         // Clear the samples for the next pushed data.
         this.samples = new Float32Array();
     }
+
+    private playAudio(audioData: ArrayBuffer): void {
+        if (this.audioContext === null) {
+            this.createAudioContext();
+        }
+        const source: AudioBufferSourceNode = this.audioContext.createBufferSource();
+        const destination: AudioDestinationNode = this.audioContext.destination;
+        this.audioContext.decodeAudioData(audioData, (newBuffer: AudioBuffer): void => {
+            source.buffer = newBuffer;
+            source.connect(destination);
+            source.start(0);
+        });
+    }
 }