Устранение гонки запуска live-камеры

apps/control-station/src/components/MseFmp4WebSocketPlayer.tsx

@@ -470,8 +470,6 @@ export function MseFmp4WebSocketPlayer({
       : "Подключение к локальному видеопотоку");
     const mediaSource = new MediaSource();
     objectUrl = URL.createObjectURL(mediaSource);
-    video.src = objectUrl;
-    startupWatchdog?.armFirstMedia();
 
     const onSourceOpen = () => {
       if (!transportIsCurrent() || failed) return;
@@ -562,7 +560,12 @@ export function MseFmp4WebSocketPlayer({
       });
     };
 
+    // Register before assigning the object URL. `video.src` is the action that
+    // lets the browser open this MediaSource; a fast sequential MSE lease must
+    // not fire `sourceopen` in the gap before its only listener exists.
     mediaSource.addEventListener("sourceopen", onSourceOpen, { once: true });
+    startupWatchdog?.armFirstMedia();
+    video.src = objectUrl;
 
     const disposeTransport = () => {
       if (disposed) return;