From 32093634709e5407251d8cd25ab025ec086d8fce Mon Sep 17 00:00:00 2001
From: Fredrik Johansson <fjon@tobii.com>
Date: Thu, 29 Jan 2026 09:31:51 +0100
Subject: [PATCH 1/2] Add UrlSourceOptions.parallelism

---
 src/source.ts | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/source.ts b/src/source.ts
index f7aa0df..eab2696 100644
--- a/src/source.ts
+++ b/src/source.ts
@@ -343,6 +343,9 @@ export type UrlSourceOptions = {
 	/** The maximum number of bytes the cache is allowed to hold in memory. Defaults to 64 MiB. */
 	maxCacheSize?: number;
 
+	/** The maximum number of parallel workers to use for fetching. Defaults to 2. */
+	parallelism?: number;
+
 	/**
 	 * A WHATWG-compatible fetch function. You can use this field to polyfill the `fetch` function, add missing
 	 * features, or use a custom implementation.
@@ -403,6 +406,9 @@ export class UrlSource extends Source {
 		) {
 			throw new TypeError('options.maxCacheSize, when provided, must be a non-negative number.');
 		}
+		if (options.parallelism !== undefined && (!isNumber(options.parallelism) || options.parallelism < 1)) {
+			throw new TypeError('options.parallelism, when provided, must be a positive number.');
+		}
 		if (options.fetchFn !== undefined && typeof options.fetchFn !== 'function') {
 			throw new TypeError('options.fetchFn, when provided, must be a function.');
 			// Won't bother validating this function beyond this
@@ -418,7 +424,7 @@ export class UrlSource extends Source {
 			maxCacheSize: options.maxCacheSize ?? (64 * 2 ** 20 /* 64 MiB */),
 			// Most files in the real-world have a single sequential access pattern, but having two in parallel can
 			// also happen
-			maxWorkerCount: 2,
+			maxWorkerCount: options.parallelism ?? 2,
 			runWorker: this._runWorker.bind(this),
 			prefetchProfile: PREFETCH_PROFILES.network,
 		});

From cab92c55ec9a0503b1d6d58af15d38116839e3ea Mon Sep 17 00:00:00 2001
From: Vanilagy <1696106+Vanilagy@users.noreply.github.com>
Date: Tue, 3 Feb 2026 16:01:46 +0100
Subject: [PATCH 2/2] Fix a few things

---
 docs/guide/reading-media-files.md |  3 +++
 src/source.ts                     | 12 +++++++-----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/docs/guide/reading-media-files.md b/docs/guide/reading-media-files.md
index 6e3faab..e83e2dd 100644
--- a/docs/guide/reading-media-files.md
+++ b/docs/guide/reading-media-files.md
@@ -506,6 +506,9 @@ type UrlSourceOptions = {
 	// in memory. Defaults to 8 MiB.
 	maxCacheSize?: number;
 
+	// The maximum number of parallel requests to use for fetching. Defaults to 2.
+	parallelism?: number;
+
 	// Used to provide a custom fetch function
 	fetchFn?: typeof fetch;
 };
diff --git a/src/source.ts b/src/source.ts
index eab2696..9a0c187 100644
--- a/src/source.ts
+++ b/src/source.ts
@@ -343,7 +343,7 @@ export type UrlSourceOptions = {
 	/** The maximum number of bytes the cache is allowed to hold in memory. Defaults to 64 MiB. */
 	maxCacheSize?: number;
 
-	/** The maximum number of parallel workers to use for fetching. Defaults to 2. */
+	/** The maximum number of parallel requests to use for fetching. Defaults to 2. */
 	parallelism?: number;
 
 	/**
@@ -406,7 +406,7 @@ export class UrlSource extends Source {
 		) {
 			throw new TypeError('options.maxCacheSize, when provided, must be a non-negative number.');
 		}
-		if (options.parallelism !== undefined && (!isNumber(options.parallelism) || options.parallelism < 1)) {
+		if (options.parallelism !== undefined && (!Number.isInteger(options.parallelism) || options.parallelism < 1)) {
 			throw new TypeError('options.parallelism, when provided, must be a positive number.');
 		}
 		if (options.fetchFn !== undefined && typeof options.fetchFn !== 'function') {
@@ -420,11 +420,13 @@ export class UrlSource extends Source {
 		this._options = options;
 		this._getRetryDelay = options.getRetryDelay ?? DEFAULT_RETRY_DELAY;
 
+		// Most files in the real-world have a single sequential access pattern, but having two in parallel can
+		// also happen
+		const DEFAULT_PARALLELISM = 2;
+
 		this._orchestrator = new ReadOrchestrator({
 			maxCacheSize: options.maxCacheSize ?? (64 * 2 ** 20 /* 64 MiB */),
-			// Most files in the real-world have a single sequential access pattern, but having two in parallel can
-			// also happen
-			maxWorkerCount: options.parallelism ?? 2,
+			maxWorkerCount: options.parallelism ?? DEFAULT_PARALLELISM,
 			runWorker: this._runWorker.bind(this),
 			prefetchProfile: PREFETCH_PROFILES.network,
 		});