diff --git a/av/pubsub/queue.go b/av/pubsub/queue.go
index 473e823..2d5a832 100644
--- a/av/pubsub/queue.go
+++ b/av/pubsub/queue.go
@@ -32,19 +32,13 @@ type Queue struct {
 	closed bool
 }
 
-func NewQueue(streams []av.CodecData) *Queue {
+func NewQueue() *Queue {
 	q := &Queue{}
 	q.buf = pktque.NewBuf()
-	q.streams = streams
 	q.maxdur = time.Second*10
 	q.lock = &sync.RWMutex{}
 	q.cond = sync.NewCond(q.lock.RLocker())
 	q.videoidx = -1
-	for i, stream := range streams {
-		if stream.Type().IsVideo() {
-			q.videoidx = i
-		}
-	}
 	return q
 }
 
@@ -55,6 +49,20 @@ func (self *Queue) SetMaxSize(size int) {
 	return
 }
 
+func (self *Queue) WriteHeader(streams []av.CodecData) {
+	self.lock.Lock()
+
+	self.streams = streams
+	for i, stream := range streams {
+		if stream.Type().IsVideo() {
+			self.videoidx = i
+		}
+	}
+	self.cond.Broadcast()
+
+	self.lock.Unlock()
+}
+
 // After Close() called, all QueueCursor's ReadPacket will return io.EOF.
 func (self *Queue) Close() (err error) {
 	self.lock.Lock()
@@ -146,9 +154,16 @@ func (self *Queue) DelayedGopCount(n int) *QueueCursor {
 }
 
 func (self *QueueCursor) Streams() (streams []av.CodecData, err error) {
-	self.que.lock.RLock()
-	streams = self.que.streams
-	self.que.lock.RUnlock()
+	self.que.cond.L.Lock()
+	for self.que.streams == nil && !self.que.closed {
+		self.que.cond.Wait()
+	}
+	if self.que.streams != nil {
+		streams = self.que.streams
+	} else {
+		err = io.EOF
+	}
+	self.que.cond.L.Unlock()
 	return
 }