[HTML5] Refactor audio drivers. Implement AudioWorklet w/o threads.

Performances are not great in general, bad on Firefox, on Chrome, well,
it could be an improvement. Leave it as a fallback for now, but can be
forced via project settings if desired (or custom JavaScript logic via
the "args" option).

I'm actually surprised this works, it involves so many allocations, but
there's no way around it when SharedArrayBuffer is not available :(.

1 files changed, 37 insertions, 12 deletions

diff --git a/platform/javascript/js/libs/audio.worklet.js b/platform/javascript/js/libs/audio.worklet.js
index df475ba52d..52b3aedf8c 100644
--- a/platform/javascript/js/libs/audio.worklet.js
+++ b/platform/javascript/js/libs/audio.worklet.js
@@ -29,15 +29,16 @@
 /*************************************************************************/
 
 class RingBuffer {
-	constructor(p_buffer, p_state) {
+	constructor(p_buffer, p_state, p_threads) {
 		this.buffer = p_buffer;
 		this.avail = p_state;
+		this.threads = p_threads;
 		this.rpos = 0;
 		this.wpos = 0;
 	}
 
 	data_left() {
-		return Atomics.load(this.avail, 0);
+		return this.threads ? Atomics.load(this.avail, 0) : this.avail;
 	}
 
 	space_left() {
@@ -55,10 +56,16 @@ class RingBuffer {
 			to_write -= high;
 			this.rpos = 0;
 		}
-		output.set(this.buffer.subarray(this.rpos, this.rpos + to_write), from);
+		if (to_write) {
+			output.set(this.buffer.subarray(this.rpos, this.rpos + to_write), from);
+		}
 		this.rpos += to_write;
-		Atomics.add(this.avail, 0, -output.length);
-		Atomics.notify(this.avail, 0);
+		if (this.threads) {
+			Atomics.add(this.avail, 0, -output.length);
+			Atomics.notify(this.avail, 0);
+		} else {
+			this.avail -= output.length;
+		}
 	}
 
 	write(p_buffer) {
@@ -77,14 +84,19 @@ class RingBuffer {
 			this.buffer.set(low);
 			this.wpos = low.length;
 		}
-		Atomics.add(this.avail, 0, to_write);
-		Atomics.notify(this.avail, 0);
+		if (this.threads) {
+			Atomics.add(this.avail, 0, to_write);
+			Atomics.notify(this.avail, 0);
+		} else {
+			this.avail += to_write;
+		}
 	}
 }
 
 class GodotProcessor extends AudioWorkletProcessor {
 	constructor() {
 		super();
+		this.threads = false;
 		this.running = true;
 		this.lock = null;
 		this.notifier = null;
@@ -100,24 +112,31 @@ class GodotProcessor extends AudioWorkletProcessor {
 	}
 
 	process_notify() {
-		Atomics.add(this.notifier, 0, 1);
-		Atomics.notify(this.notifier, 0);
+		if (this.notifier) {
+			Atomics.add(this.notifier, 0, 1);
+			Atomics.notify(this.notifier, 0);
+		}
 	}
 
 	parse_message(p_cmd, p_data) {
 		if (p_cmd === 'start' && p_data) {
 			const state = p_data[0];
 			let idx = 0;
+			this.threads = true;
 			this.lock = state.subarray(idx, ++idx);
 			this.notifier = state.subarray(idx, ++idx);
 			const avail_in = state.subarray(idx, ++idx);
 			const avail_out = state.subarray(idx, ++idx);
-			this.input = new RingBuffer(p_data[1], avail_in);
-			this.output = new RingBuffer(p_data[2], avail_out);
+			this.input = new RingBuffer(p_data[1], avail_in, true);
+			this.output = new RingBuffer(p_data[2], avail_out, true);
 		} else if (p_cmd === 'stop') {
 			this.running = false;
 			this.output = null;
 			this.input = null;
+		} else if (p_cmd === 'start_nothreads') {
+			this.output = new RingBuffer(p_data[0], p_data[0].length, false);
+		} else if (p_cmd === 'chunk') {
+			this.output.write(p_data);
 		}
 	}
 
@@ -139,7 +158,10 @@ class GodotProcessor extends AudioWorkletProcessor {
 			if (this.input_buffer.length !== chunk) {
 				this.input_buffer = new Float32Array(chunk);
 			}
-			if (this.input.space_left() >= chunk) {
+			if (!this.threads) {
+				GodotProcessor.write_input(this.input_buffer, input);
+				this.port.postMessage({ 'cmd': 'input', 'data': this.input_buffer });
+			} else if (this.input.space_left() >= chunk) {
 				GodotProcessor.write_input(this.input_buffer, input);
 				this.input.write(this.input_buffer);
 			} else {
@@ -156,6 +178,9 @@ class GodotProcessor extends AudioWorkletProcessor {
 			if (this.output.data_left() >= chunk) {
 				this.output.read(this.output_buffer);
 				GodotProcessor.write_output(output, this.output_buffer);
+				if (!this.threads) {
+					this.port.postMessage({ 'cmd': 'read', 'data': chunk });
+				}
 			} else {
 				this.port.postMessage('Output buffer has not enough frames! Skipping output frame.');
 			}