diff --git a/rtmp.go b/rtmp.go
index cbd3b6b..c1a2d79 100644
--- a/rtmp.go
+++ b/rtmp.go
@@ -708,7 +708,11 @@ func (self *Conn) ReadPacket() (pkt av.Packet, err error) {
 		switch tag := _tag.(type) {
 		case *flvio.Videodata:
 			pkt.CompositionTime = tsToTime(uint32(tag.CompositionTime))
-			pkt.Data = tag.Data
+			if typ := h264parser.CheckNALUsType(tag.Data); typ != h264parser.NALU_AVCC {
+				err = fmt.Errorf("rtmp: input h264 nalu format=%d invalid", typ)
+				return
+			}
+			pkt.Data = tag.Data[4:]
 			pkt.IsKeyFrame = tag.FrameType == flvio.FRAME_KEY
 			pkt.Idx = int8(self.videostreamidx)
 			break poll
@@ -809,7 +813,14 @@ func (self *Conn) WritePacket(pkt av.Packet) (err error) {
 		}
 
 	case av.H264:
-		videodata := self.makeH264Videodata(flvio.AVC_NALU, pkt.IsKeyFrame, pkt.Data)
+		if typ := h264parser.CheckNALUsType(pkt.Data); typ != h264parser.NALU_RAW {
+			err = fmt.Errorf("rtmp: h264 nalu format=%d invalid", typ)
+			return
+		}
+		var b [4]byte
+		pio.PutU32BE(b[:], uint32(len(pkt.Data)))
+		videodata := self.makeH264Videodata(flvio.AVC_NALU, pkt.IsKeyFrame, []byte{})
+		videodata.Datav = [][]byte{b[:], pkt.Data}
 		videodata.CompositionTime = int32(timeToTs(pkt.CompositionTime))
 		w := self.writeVideoDataStart()
 		videodata.Marshal(w)