diff --git a/format/rtmp/rtmp.go b/format/rtmp/rtmp.go
index 2dd5165..3450aaf 100644
--- a/format/rtmp/rtmp.go
+++ b/format/rtmp/rtmp.go
@@ -303,6 +303,7 @@ func NewConn(netconn net.Conn) *Conn {
 	conn.readcsmap = make(map[uint32]*chunkStream)
 	conn.readMaxChunkSize = 128
 	conn.writeMaxChunkSize = 128
+	conn.readAckSize = 1048576
 	conn.txrxcount = &txrxcount{ReadWriter: netconn}
 	conn.bufr = bufio.NewReaderSize(conn.txrxcount, pio.RecommendBufioSize)
 	conn.bufw = bufio.NewWriterSize(conn.txrxcount, pio.RecommendBufioSize)
@@ -319,6 +320,7 @@ type chunkStream struct {
 	gentimenow  bool
 	timedelta   uint32
 	hastimeext  bool
+	timeext     uint32
 	msgsid      uint32
 	msgtypeid   uint8
 	msgdatalen  uint32
@@ -791,7 +793,7 @@ func (conn *Conn) writeConnect(path string) (err error) {
 		} else {
 			if conn.msgtypeid == msgtypeidWindowAckSize {
 				if len(conn.msgdata) == 4 {
-					conn.readAckSize = pio.U32BE(conn.msgdata)
+					conn.readAckSize = pio.U32BE(conn.msgdata) >> 1
 				}
 				//if err = self.writeWindowAckSize(0xffffffff); err != nil {
 				//	return
@@ -1375,10 +1377,17 @@ func (conn *Conn) readChunk() (err error) {
 		csid = uint32(pio.U16BE(b)) + 64
 	}
 
+	newcs := false
 	cs := conn.readcsmap[csid]
 	if cs == nil {
 		cs = &chunkStream{}
 		conn.readcsmap[csid] = cs
+		newcs = true
+	}
+
+	if len(conn.readcsmap) > 16 {
+		err = fmt.Errorf("too many chunk stream ids")
+		return
 	}
 
 	var timestamp uint32
@@ -1419,6 +1428,7 @@ func (conn *Conn) readChunk() (err error) {
 			n += 4
 			timestamp = pio.U32BE(b)
 			cs.hastimeext = true
+			cs.timeext = timestamp
 		} else {
 			cs.hastimeext = false
 		}
@@ -1435,6 +1445,10 @@ func (conn *Conn) readChunk() (err error) {
 		// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 		//
 		//       Figure 10 Chunk Message Header – Type 1
+		if newcs {
+			err = fmt.Errorf("chunk message type 1 without previous chunk")
+			return
+		}
 		if cs.msgdataleft != 0 {
 			if !conn.skipInvalidMessages {
 				err = fmt.Errorf("chunk msgdataleft=%d invalid", cs.msgdataleft)
@@ -1457,6 +1471,7 @@ func (conn *Conn) readChunk() (err error) {
 			n += 4
 			timestamp = pio.U32BE(b)
 			cs.hastimeext = true
+			cs.timeext = timestamp
 		} else {
 			cs.hastimeext = false
 		}
@@ -1472,6 +1487,10 @@ func (conn *Conn) readChunk() (err error) {
 		// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 		//
 		//       Figure 11 Chunk Message Header – Type 2
+		if newcs {
+			err = fmt.Errorf("chunk message type 2 without previous chunk")
+			return
+		}
 		if cs.msgdataleft != 0 {
 			if !conn.skipInvalidMessages {
 				err = fmt.Errorf("chunk msgdataleft=%d invalid", cs.msgdataleft)
@@ -1492,6 +1511,7 @@ func (conn *Conn) readChunk() (err error) {
 			n += 4
 			timestamp = pio.U32BE(b)
 			cs.hastimeext = true
+			cs.timeext = timestamp
 		} else {
 			cs.hastimeext = false
 		}
@@ -1500,6 +1520,11 @@ func (conn *Conn) readChunk() (err error) {
 		cs.Start()
 
 	case 3:
+		if newcs {
+			err = fmt.Errorf("chunk message type 3 without previous chunk")
+			return
+		}
+
 		if cs.msgdataleft == 0 {
 			switch cs.msghdrtype {
 			case 0:
@@ -1510,6 +1535,7 @@ func (conn *Conn) readChunk() (err error) {
 					n += 4
 					timestamp = pio.U32BE(b)
 					cs.timenow = timestamp
+					cs.timeext = timestamp
 				}
 			case 1, 2:
 				if cs.hastimeext {
@@ -1524,6 +1550,18 @@ func (conn *Conn) readChunk() (err error) {
 				cs.timenow += timestamp
 			}
 			cs.Start()
+		} else {
+			if cs.hastimeext {
+				var b []byte
+				if b, err = conn.bufr.Peek(4); err != nil {
+					return
+				}
+				if pio.U32BE(b) == cs.timeext {
+					if _, err = io.ReadFull(conn.bufr, b[:4]); err != nil {
+						return
+					}
+				}
+			}
 		}
 
 	default:
@@ -1545,12 +1583,12 @@ func (conn *Conn) readChunk() (err error) {
 
 	if Debug {
 		fmt.Printf("rtmp: chunk msgsid=%d msgtypeid=%d msghdrtype=%d len=%d left=%d max=%d",
-			cs.msgsid, cs.msgtypeid, cs.msghdrtype, cs.msgdatalen, cs.msgdataleft, conn.readMaxChunkSize)
+			cs.msgsid, cs.msgtypeid, msghdrtype, cs.msgdatalen, cs.msgdataleft, conn.readMaxChunkSize)
 	}
 
 	if conn.debugChunks {
-		data := fmt.Sprintf("rtmp: chunk id=%d msgsid=%d msgtypeid=%d msghdrtype=%d timestamp=%d len=%d left=%d max=%d",
-			csid, cs.msgsid, cs.msgtypeid, cs.msghdrtype, cs.timenow, cs.msgdatalen, cs.msgdataleft, conn.readMaxChunkSize)
+		data := fmt.Sprintf("rtmp: chunk id=%d msgsid=%d msgtypeid=%d msghdrtype=%d timestamp=%d ext=%v len=%d left=%d max=%d",
+			csid, cs.msgsid, cs.msgtypeid, msghdrtype, cs.timenow, cs.hastimeext, cs.msgdatalen, cs.msgdataleft, conn.readMaxChunkSize)
 
 		if cs.msgtypeid != msgtypeidVideoMsg && cs.msgtypeid != msgtypeidAudioMsg {
 			if len(cs.msgdata) > 1024 {
@@ -1603,6 +1641,8 @@ func (conn *Conn) readChunk() (err error) {
 		if err = conn.handleMsg(timestamp, cs.msgsid, cs.msgtypeid, cs.msgdata); err != nil {
 			return fmt.Errorf("handleMsg: %w", err)
 		}
+
+		cs.msgdata = nil
 	}
 
 	conn.ackn += uint32(n)
@@ -1773,7 +1813,7 @@ func (conn *Conn) handleMsg(timestamp uint32, msgsid uint32, msgtypeid uint8, ms
 		if len(conn.msgdata) != 4 {
 			return fmt.Errorf("invalid packet of WindowAckSize")
 		}
-		conn.readAckSize = pio.U32BE(conn.msgdata)
+		conn.readAckSize = pio.U32BE(conn.msgdata) >> 1
 	default:
 		if Debug {
 			fmt.Printf("rtmp: unhandled msg: %d\n", msgtypeid)