Fix async race condition bug

dev/convert.html

@@ -21,7 +21,7 @@
 			chunked: true,
 			chunkSize: 2**20
 		});
-		const outputFormat = new Metamuxer.OggOutputFormat();
+		const outputFormat = new Metamuxer.WavOutputFormat();
 
 		const button = document.createElement('button');
 		button.textContent = 'Cancel';
@@ -77,10 +77,10 @@
 				//width: 200,
 				//height: 100,
 			},
-			trim: {
-				start: 0,
-				end: 30
-			},
+			//trim: {
+			//	start: 0,
+			//	end: 30
+			//},
 			computeProgress: true
 		});
 		console.log(conversion);
@@ -108,7 +108,7 @@
 		document.body.append(video);
 		video.play();
 
-		//download(new Blob([target.buffer]), 'converted' + outputFormat.fileExtension);
+		download(new Blob([target.buffer]), 'converted' + outputFormat.fileExtension);
 
 		function download(blob, filename) {
 			const url = URL.createObjectURL(blob);

dev/mux.html

@@ -43,6 +43,7 @@
 	format = new Metamuxer.OggOutputFormat();
 	format = new Metamuxer.Mp4OutputFormat({ fastStart: 'fragmented', minimumFragmentDuration: 2 });
 	format = new Metamuxer.MkvOutputFormat({ minimumClusterDuration: 2 });
+	format = new Metamuxer.WavOutputFormat();
 	let target = new Metamuxer.BufferTarget();
 
 	/*
@@ -57,6 +58,30 @@
 
 	let output = new Metamuxer.Output({ format, target });
 
+	let sourcy = new Metamuxer.AudioBufferSource({
+		codec: 'pcm-s16',
+		bitrate: Metamuxer.QUALITY_HIGH
+	});
+	output.addAudioTrack(sourcy);
+
+	await output.start();
+
+	for (let i = 0; i < 1000; i++) {
+		let buf = new AudioBuffer({
+			length: 1024,
+			sampleRate: 48000,
+			numberOfChannels: 2
+		});
+		sourcy.add(buf);
+	}
+
+	console.log("Done")
+
+	
+	await output.finalize();
+
+	await new Promise(() => {});
+
 	/*
 	let videoSource = new Metamuxer.EncodedVideoChunkSource('avc');
 	output.addTrack(videoSource);

src/media-source.ts

@@ -278,10 +278,16 @@ class VideoEncoderWrapper {
 		}
 
 		if (!this.encoderInitialized) {
-			if (this.ensureEncoderPromise) {
+			if (!this.ensureEncoderPromise) {
+				void this.ensureEncoder(videoSample);
+			}
+
+			// No, this "if" statement is not useless. Sometimes, the above call to `ensureEncoder` might have
+			// synchronously completed and the encoder is already initialized. In this case, we don't need to await the
+			// promise anymore. This also fixes nasty async race condition bugs when multiple code paths are calling
+			// this method: It's important that the call that initialized the encoder go through this code first.
+			if (!this.encoderInitialized) {
 				await this.ensureEncoderPromise;
-			} else {
-				await this.ensureEncoder(videoSample);
 			}
 		}
 		assert(this.encoderInitialized);
@@ -763,10 +769,16 @@ class AudioEncoderWrapper {
 		}
 
 		if (!this.encoderInitialized) {
-			if (this.ensureEncoderPromise) {
+			if (!this.ensureEncoderPromise) {
+				void this.ensureEncoder(audioSample);
+			}
+
+			// No, this "if" statement is not useless. Sometimes, the above call to `ensureEncoder` might have
+			// synchronously completed and the encoder is already initialized. In this case, we don't need to await the
+			// promise anymore. This also fixes nasty async race condition bugs when multiple code paths are calling
+			// this method: It's important that the call that initialized the encoder go through this code first.
+			if (!this.encoderInitialized) {
 				await this.ensureEncoderPromise;
-			} else {
-				await this.ensureEncoder(audioSample);
 			}
 		}
 		assert(this.encoderInitialized);