feat(pcm-player): improve buffering (023492fb) · Commits · e / tools / webadb

libraries/pcm-player/worker/worker.ts

+44 −23

Original line number	Diff line number	Diff line
		const SAMPLE_RATE = 48000;

		abstract class SourceProcessor<T>
		extends AudioWorkletProcessor
		implements AudioWorkletProcessorImpl
		{
		#sources: T[] = [];
		#sourceSampleCount = 0;
		#chunks: T[] = [];
		#chunkSampleCounts: number[] = [];
		#totalSampleCount = 0;
		#speedUp = false;

		constructor() {
		super();
		this.port.onmessage = (event) => {
		// Throw away old chunks when buffer is exceeding 0.2s
		while (this.#totalSampleCount > SAMPLE_RATE * 0.2) {
		this.#chunks.shift();
		const count = this.#chunkSampleCounts.shift()!;
		this.#totalSampleCount -= count;
		}

		const data = event.data as ArrayBuffer[];
		const [source, length] = this.createSource(data);
		this.#sources.push(source);
		this.#sourceSampleCount += length;
		this.#chunks.push(source);
		this.#chunkSampleCounts.push(length);
		this.#totalSampleCount += length;

		// Speed up when buffer is exceeding 0.1s
		if (this.#totalSampleCount > SAMPLE_RATE * 0.1) {
		this.#speedUp = true;
		}
		};
		}

		@@ -23,16 +40,18 @@ abstract class SourceProcessor<T>
		const outputLength = outputLeft.length;
		let outputIndex = 0;

		// Resample source catch up with output
		// TODO: should we limit the minimum and maximum speed?
		// TODO: this simple resample method changes pitch
		const sourceIndexStep = this.#sourceSampleCount > 48000 ? 1.02 : 1;
		// Stop speeding up when buffer is below 0.05s
		if (this.#speedUp && this.#totalSampleCount < SAMPLE_RATE * 0.05) {
		this.#speedUp = false;
		}

		const sourceIndexStep = this.#speedUp ? 1.02 : 1;
		let sourceIndex = 0;

		while (this.#sources.length > 0 && outputIndex < outputLength) {
		while (this.#chunks.length > 0 && outputIndex < outputLength) {
		const beginSourceIndex = sourceIndex \| 0;

		let source: T \| undefined = this.#sources[0];
		let source: T \| undefined = this.#chunks[0];
		[source, sourceIndex, outputIndex] = this.copyChunk(
		sourceIndex,
		sourceIndexStep,
		@@ -40,27 +59,29 @@ abstract class SourceProcessor<T>
		outputLeft,
		outputRight,
		outputLength,
		outputIndex
		outputIndex,
		);

		const consumedSampleCount = (sourceIndex \| 0) - beginSourceIndex;
		this.#sourceSampleCount -= consumedSampleCount;
		this.#totalSampleCount -= consumedSampleCount;
		sourceIndex -= consumedSampleCount;

		if (source) {
		// Output full
		this.#sources[0] = source;
		this.#chunks[0] = source;
		this.#chunkSampleCounts[0]! -= consumedSampleCount;
		return true;
		}

		this.#sources.shift();
		this.#chunks.shift();
		this.#chunkSampleCounts.shift();
		}

		if (outputIndex < outputLength) {
		console.log(
		`[Audio] Buffer underflow, inserting silence: ${
		outputLength - outputIndex
		} samples`
		} samples`,
		);
		}

		@@ -74,7 +95,7 @@ abstract class SourceProcessor<T>
		outputLeft: Float32Array,
		outputRight: Float32Array,
		outputLength: number,
		outputIndex: number
		outputIndex: number,
		): [source: T \| undefined, sourceIndex: number, outputIndex: number];
		}

		@@ -94,7 +115,7 @@ class Int16SourceProcessor
		outputLeft: Float32Array,
		outputRight: Float32Array,
		outputLength: number,
		outputIndex: number
		outputIndex: number,
		): [
		source: Int16Array \| undefined,
		sourceIndex: number,
		@@ -128,7 +149,7 @@ class Int16SourceProcessor

		class Float32SourceProcessor extends SourceProcessor<Float32Array> {
		protected override createSource(
		data: ArrayBuffer[]
		data: ArrayBuffer[],
		): [Float32Array, number] {
		const source = new Float32Array(data[0]!);
		return [source, source.length / 2];
		@@ -141,7 +162,7 @@ class Float32SourceProcessor extends SourceProcessor<Float32Array> {
		outputLeft: Float32Array,
		outputRight: Float32Array,
		outputLength: number,
		outputIndex: number
		outputIndex: number,
		): [
		source: Float32Array \| undefined,
		sourceIndex: number,
		@@ -175,7 +196,7 @@ class Float32SourceProcessor extends SourceProcessor<Float32Array> {

		class Float32PlanerSourceProcessor extends SourceProcessor<Float32Array[]> {
		protected override createSource(
		data: ArrayBuffer[]
		data: ArrayBuffer[],
		): [Float32Array[], number] {
		const source = data.map((channel) => new Float32Array(channel));
		return [source, source[0]!.length];
		@@ -188,7 +209,7 @@ class Float32PlanerSourceProcessor extends SourceProcessor<Float32Array[]> {
		outputLeft: Float32Array,
		outputRight: Float32Array,
		outputLength: number,
		outputIndex: number
		outputIndex: number,
		): [
		source: Float32Array[] \| undefined,
		sourceIndex: number,
		@@ -211,7 +232,7 @@ class Float32PlanerSourceProcessor extends SourceProcessor<Float32Array[]> {
		return [
		sourceSampleIndex < sourceLength
		? source.map((channel) =>
		channel.subarray(sourceSampleIndex)
		channel.subarray(sourceSampleIndex),
		)
		: undefined,
		sourceIndex,
		@@ -228,5 +249,5 @@ registerProcessor("int16-source-processor", Int16SourceProcessor);
		registerProcessor("float32-source-processor", Float32SourceProcessor);
		registerProcessor(
		"float32-planer-source-processor",
		Float32PlanerSourceProcessor
		Float32PlanerSourceProcessor,
		);