同步上游 0921 版 zip（新增 emby 播放等 20 处变更）

internal/app/ui_playback.go

@@ -15,7 +15,6 @@ import (
 )
 
 const playbackIdleTimeout = 10 * time.Minute
-const playbackSessionLimit = 4
 const playbackMIME = `video/mp4; codecs="avc1.42C01F, mp4a.40.2"`
 
 type playbackSession struct {
@@ -41,6 +40,9 @@ type playbackSession struct {
 	mediaReady      chan struct{}
 	mediaError      error
 	mediaWaiters    int
+	emby            bool
+	embyLegacy      bool
+	embyProcessing  string
 	quality         int
 	streamVersion   uint64
 	openedAt        time.Time
@@ -252,7 +254,7 @@ func (app *UIApp) handlePlaybackOpen(writer http.ResponseWriter, request *http.R
 		return
 	}
 	app.playbackMu.Lock()
-	if len(app.playbacks) >= app.mediaResources().snapshot().MaxSessions {
+	if app.activePlaybackSessionsLocked() >= app.mediaResources().snapshot().MaxSessions {
 		app.playbackMu.Unlock()
 		writeJSON(writer, http.StatusTooManyRequests, map[string]string{"error": "同时播放数量已达上限，请稍后再试"})
 		return