Also put the this._sync assignment inside setImmediate

src/media/BaseMediaStream.ts

@@ -29,28 +29,29 @@ export class BaseMediaStream extends Writable {
         return this._sync;
     }
     set sync(val: boolean) {
-        this._sync = val;
-        if (val)
-        {
-            // Reset timestamp stats when enabling sync
-            /**
-             * Since _waitForOtherStream() is an async function, it can only
-             * return at the end of the event loop, while Node.js is processing
-             * the microtask queue. If this is run synchronously, it can set
-             * _startTime to undefined before _waitForOtherStream() returns,
-             * which will cause the timeout calculation below to return NaN.
-             * Use setImmediate to put this on the macrotask queue, which is
-             * processed after the microtask queue.
-             */
-            setImmediate(() => {
+        /**
+          * Since _waitForOtherStream() is an async function, it can only
+          * return at the end of the event loop, while Node.js is processing
+          * the microtask queue. If this is run synchronously, it can interfere
+          * with the operation of _waitForOtherStream().
+          * Use setImmediate to put this on the macrotask queue, which is
+          * processed after the microtask queue. This comes with the side effect
+          * of the value being incorrect until the next turn of the event loop,
+          * but it avoids all data race issues
+          */
+        setImmediate(() => {
+            this._sync = val;
+            if (val)
+            {
+                // Reset timestamp stats when enabling sync
                 this._startPts = this._startTime = undefined;
                 this._loggerSync.debug("Sync enabled");
-            });
-        }
-        else
-        {
-            this._loggerSync.debug("Sync disabled");
-        }
+            }
+            else
+            {
+                this._loggerSync.debug("Sync disabled");
+            }
+        });
     }
     get noSleep(): boolean {
         return this._noSleep;