diff --git a/pktqueue/pktqueue.go b/pktqueue/pktqueue.go
index 372c6b6..3145e7b 100644
--- a/pktqueue/pktqueue.go
+++ b/pktqueue/pktqueue.go
@@ -11,22 +11,33 @@ type timePacket struct {
 
 type stream struct {
 	pkts []timePacket
-	lastDuration float64
+	lastNormalDuration float64
+	isVideo bool
+}
+
+func (self *stream) isDurationNormal(v float64) bool {
+	return v > float64(0.0) && v < float64(1.0)
 }
 
 func (self *stream) Read(flush bool) (ok bool, pkt timePacket) {
 	if len(self.pkts) > 1 {
 		ok = true
-		pkt := self.pkts[0]
+		pkt = self.pkts[0]
 		pkt.Duration = self.pkts[1].time - self.pkts[0].time
-		self.lastDuration = pkt.Duration
 		self.pkts = self.pkts[1:]
 	} else if len(self.pkts) == 1 && flush {
 		ok = true
-		pkt := self.pkts[0]
-		pkt.Duration = self.lastDuration
+		pkt = self.pkts[0]
+		pkt.Duration = self.lastNormalDuration
 		self.pkts = self.pkts[1:]
 	}
+	if ok {
+		if !self.isDurationNormal(pkt.Duration) {
+			pkt.Duration = self.lastNormalDuration
+		} else {
+			self.lastNormalDuration = pkt.Duration
+		}
+	}
 	return
 }
 
@@ -41,12 +52,20 @@ func (self *Queue) CurrentTime() float64 {
 	return self.time
 }
 
-func (self *Queue) Alloc(n int) {
-	self.streams = make([]*stream, n)
+func (self *Queue) Alloc(streams []av.CodecData) {
+	self.streams = make([]*stream, len(streams))
+	for i := 0; i < len(self.streams); i++ {
+		self.streams[i] = &stream{
+			isVideo: streams[i].IsVideo(),
+		}
+	}
 }
 
 func (self *Queue) Clear() {
-	self.Alloc(len(self.streams))
+	for _, stream := range self.streams {
+		stream.pkts = []timePacket{}
+		stream.lastNormalDuration = float64(0.0)
+	}
 	self.time = 0.0
 }