diff --git a/av/pktque/buf.go b/av/pktque/buf.go
index 70b890f..6624f55 100644
--- a/av/pktque/buf.go
+++ b/av/pktque/buf.go
@@ -5,33 +5,31 @@ import (
 )
 
 type Buf struct {
-	Head, Tail    BufPos
-	pkts          []av.Packet
-	size, maxsize int
-	count         int
+	Head, Tail BufPos
+	pkts       []av.Packet
+	Size       int
+	Count      int
 }
 
 func NewBuf() *Buf {
 	return &Buf{
-		pkts:    make([]av.Packet, 64),
-		maxsize: 1024 * 512,
+		pkts: make([]av.Packet, 64),
 	}
 }
 
-func (self *Buf) SetMaxSize(size int) {
-	self.maxsize = size
-	self.shrink()
-}
-
-func (self *Buf) shrink() {
-	for self.size > self.maxsize && self.count > 1 {
-		i := int(self.Head) & (len(self.pkts) - 1)
-		pkt := self.pkts[i]
-		self.pkts[i] = av.Packet{}
-		self.size -= len(pkt.Data)
-		self.Head++
-		self.count--
+func (self *Buf) Pop() av.Packet {
+	if self.Count == 0 {
+		panic("pktque.Buf: Pop() when count == 0")
 	}
+
+	i := int(self.Head) & (len(self.pkts) - 1)
+	pkt := self.pkts[i]
+	self.pkts[i] = av.Packet{}
+	self.Size -= len(pkt.Data)
+	self.Head++
+	self.Count--
+
+	return pkt
 }
 
 func (self *Buf) grow() {
@@ -43,14 +41,13 @@ func (self *Buf) grow() {
 }
 
 func (self *Buf) Push(pkt av.Packet) {
-	if self.count == len(self.pkts) {
+	if self.Count == len(self.pkts) {
 		self.grow()
 	}
 	self.pkts[int(self.Tail)&(len(self.pkts)-1)] = pkt
 	self.Tail++
-	self.count++
-	self.size += len(pkt.Data)
-	self.shrink()
+	self.Count++
+	self.Size += len(pkt.Data)
 }
 
 func (self *Buf) Get(pos BufPos) av.Packet {
diff --git a/av/pubsub/queue.go b/av/pubsub/queue.go
index 2d5a832..9c5c32c 100644
--- a/av/pubsub/queue.go
+++ b/av/pubsub/queue.go
@@ -1,4 +1,3 @@
-
 // Packege pubsub implements publisher-subscribers model used in multi-channel streaming.
 package pubsub
 
@@ -6,45 +5,45 @@ import (
 	"github.com/nareix/joy4/av"
 	"github.com/nareix/joy4/av/pktque"
 	"io"
-	"time"
 	"sync"
+	"time"
 )
 
 //        time
 // ----------------->
-// 
+//
 // V-A-V-V-A-V-V-A-V-V
 // |                 |
 // 0        5        10
 // head             tail
 // oldest          latest
-// 
+//
 
 // One publisher and multiple subscribers thread-safe packet buffer queue.
 type Queue struct {
-	buf *pktque.Buf
-	head, tail int
-	lock *sync.RWMutex
-	cond *sync.Cond
-	maxdur time.Duration
-	streams []av.CodecData
-	videoidx int
-	closed bool
+	buf                      *pktque.Buf
+	head, tail               int
+	lock                     *sync.RWMutex
+	cond                     *sync.Cond
+	curgopcount, maxgopcount int
+	streams                  []av.CodecData
+	videoidx                 int
+	closed                   bool
 }
 
 func NewQueue() *Queue {
 	q := &Queue{}
 	q.buf = pktque.NewBuf()
-	q.maxdur = time.Second*10
+	q.maxgopcount = 2
 	q.lock = &sync.RWMutex{}
 	q.cond = sync.NewCond(q.lock.RLocker())
 	q.videoidx = -1
 	return q
 }
 
-func (self *Queue) SetMaxSize(size int) {
+func (self *Queue) SetMaxGopCount(n int) {
 	self.lock.Lock()
-	self.buf.SetMaxSize(size)
+	self.maxgopcount = n
 	self.lock.Unlock()
 	return
 }
@@ -79,6 +78,21 @@ func (self *Queue) WritePacket(pkt av.Packet) (err error) {
 	self.lock.Lock()
 
 	self.buf.Push(pkt)
+	if pkt.Idx == int8(self.videoidx) && pkt.IsKeyFrame {
+		self.curgopcount++
+	}
+
+	for self.curgopcount >= self.maxgopcount && self.buf.Count > 1 {
+		pkt := self.buf.Pop()
+		if pkt.Idx == int8(self.videoidx) && pkt.IsKeyFrame {
+			self.curgopcount--
+		}
+		if self.curgopcount < self.maxgopcount {
+			break
+		}
+	}
+	//println("shrink", self.curgopcount, self.maxgopcount, self.buf.Head, self.buf.Tail, "count", self.buf.Count, "size", self.buf.Size)
+
 	self.cond.Broadcast()
 
 	self.lock.Unlock()
@@ -86,10 +100,10 @@ func (self *Queue) WritePacket(pkt av.Packet) (err error) {
 }
 
 type QueueCursor struct {
-	que *Queue
-	pos pktque.BufPos
+	que    *Queue
+	pos    pktque.BufPos
 	gotpos bool
-	init func(buf *pktque.Buf, videoidx int) pktque.BufPos
+	init   func(buf *pktque.Buf, videoidx int) pktque.BufPos
 }
 
 func (self *Queue) newCursor() *QueueCursor {
@@ -120,11 +134,11 @@ func (self *Queue) Oldest() *QueueCursor {
 func (self *Queue) DelayedTime(dur time.Duration) *QueueCursor {
 	cursor := self.newCursor()
 	cursor.init = func(buf *pktque.Buf, videoidx int) pktque.BufPos {
-		i := buf.Tail-1
+		i := buf.Tail - 1
 		if buf.IsValidPos(i) {
 			end := buf.Get(i)
 			for buf.IsValidPos(i) {
-				if end.Time - buf.Get(i).Time > dur {
+				if end.Time-buf.Get(i).Time > dur {
 					break
 				}
 				i--
@@ -139,7 +153,7 @@ func (self *Queue) DelayedTime(dur time.Duration) *QueueCursor {
 func (self *Queue) DelayedGopCount(n int) *QueueCursor {
 	cursor := self.newCursor()
 	cursor.init = func(buf *pktque.Buf, videoidx int) pktque.BufPos {
-		i := buf.Tail-1
+		i := buf.Tail - 1
 		if videoidx != -1 {
 			for gop := 0; buf.IsValidPos(i) && gop < n; i-- {
 				pkt := buf.Get(i)
@@ -195,4 +209,3 @@ func (self *QueueCursor) ReadPacket() (pkt av.Packet, err error) {
 	self.que.cond.L.Unlock()
 	return
 }
-