diff --git a/app/demo/modflvfile/modflvfile.go b/app/demo/modflvfile/modflvfile.go
index 70c92f7..16af23e 100644
--- a/app/demo/modflvfile/modflvfile.go
+++ b/app/demo/modflvfile/modflvfile.go
@@ -77,7 +77,7 @@ func main() {
 
 func parseFlag() (string, string) {
 	i := flag.String("i", "", "specify input flv file")
-	o := flag.String("o", "", "specify ouput flv file")
+	o := flag.String("o", "", "specify output flv file")
 	flag.Parse()
 	if *i == "" || *o == "" {
 		flag.Usage()
diff --git a/app/demo/pullrtmp/pullrtmp.go b/app/demo/pullrtmp/pullrtmp.go
index 227e44f..90f9c7e 100644
--- a/app/demo/pullrtmp/pullrtmp.go
+++ b/app/demo/pullrtmp/pullrtmp.go
@@ -39,7 +39,7 @@ import (
 //   -n int
 //     	num of pull connection (default 1)
 //   -o string
-//     	specify ouput flv file
+//     	specify output flv file
 // Example:
 //   ./bin/pullrtmp -i rtmp://127.0.0.1:1935/live/test -o out.flv
 //   ./bin/pullrtmp -i rtmp://127.0.0.1:1935/live/test -n 1000
@@ -133,7 +133,7 @@ func collect(urlTmpl string, fileNameTmpl string, num int) (urls []string, filen
 
 func parseFlag() (urlTmpl string, fileNameTmpl string, num int) {
 	i := flag.String("i", "", "specify pull rtmp url")
-	o := flag.String("o", "", "specify ouput flv file")
+	o := flag.String("o", "", "specify output flv file")
 	n := flag.Int("n", 1, "specify num of pull connection")
 	flag.Parse()
 	if *i == "" {
diff --git a/app/demo/pullrtmp2hls/pullrtmp2hls.go b/app/demo/pullrtmp2hls/pullrtmp2hls.go
index cfd7045..45ff419 100644
--- a/app/demo/pullrtmp2hls/pullrtmp2hls.go
+++ b/app/demo/pullrtmp2hls/pullrtmp2hls.go
@@ -62,7 +62,7 @@ func main() {
 
 func parseFlag() (url string, hlsOutPath string, fragmentDurationMs int, fragmentNum int) {
 	i := flag.String("i", "", "specify pull rtmp url")
-	o := flag.String("o", "", "specify ouput hls file")
+	o := flag.String("o", "", "specify output hls file")
 	d := flag.Int("d", 3000, "specify duration of each ts file in millisecond")
 	n := flag.Int("n", 6, "specify num of ts file in live m3u8 list")
 	flag.Parse()
diff --git a/app/demo/pullrtsp/pullrtsp.go b/app/demo/pullrtsp/pullrtsp.go
index 81b96c8..9269005 100644
--- a/app/demo/pullrtsp/pullrtsp.go
+++ b/app/demo/pullrtsp/pullrtsp.go
@@ -69,7 +69,7 @@ func main() {
 
 func parseFlag() (inUrl string, outFilename string, overTcp int) {
 	i := flag.String("i", "", "specify pull rtsp url")
-	o := flag.String("o", "", "specify ouput flv file")
+	o := flag.String("o", "", "specify output flv file")
 	t := flag.Int("t", 0, "specify interleaved mode(rtp/rtcp over tcp)")
 	flag.Parse()
 	if *i == "" || *o == "" {