diff --git a/pkg/core/codec.go b/pkg/core/codec.go
index 50fc58ea..5f346739 100644
--- a/pkg/core/codec.go
+++ b/pkg/core/codec.go
@@ -68,7 +68,7 @@ func (c *Codec) Match(remote *Codec) bool {
 }
 
 func UnmarshalCodec(md *sdp.MediaDescription, payloadType string) *Codec {
-	c := &Codec{PayloadType: byte(atoi(payloadType))}
+	c := &Codec{PayloadType: byte(Atoi(payloadType))}
 
 	for _, attr := range md.Attributes {
 		switch {
@@ -78,7 +78,7 @@ func UnmarshalCodec(md *sdp.MediaDescription, payloadType string) *Codec {
 
 			c.Name = strings.ToUpper(ss[0])
 			// fix tailing space: `a=rtpmap:96 H264/90000 `
-			c.ClockRate = uint32(atoi(strings.TrimRightFunc(ss[1], unicode.IsSpace)))
+			c.ClockRate = uint32(Atoi(strings.TrimRightFunc(ss[1], unicode.IsSpace)))
 
 			if len(ss) == 3 && ss[2] == "2" {
 				c.Channels = 2
@@ -120,11 +120,6 @@ func UnmarshalCodec(md *sdp.MediaDescription, payloadType string) *Codec {
 	return c
 }
 
-func atoi(s string) (i int) {
-	i, _ = strconv.Atoi(s)
-	return
-}
-
 func DecodeH264(fmtp string) string {
 	if ps := Between(fmtp, "sprop-parameter-sets=", ","); ps != "" {
 		if sps, _ := base64.StdEncoding.DecodeString(ps); len(sps) >= 4 {
diff --git a/pkg/core/helpers.go b/pkg/core/helpers.go
index 060894df..44d24953 100644
--- a/pkg/core/helpers.go
+++ b/pkg/core/helpers.go
@@ -41,6 +41,11 @@ func Between(s, sub1, sub2 string) string {
 	return s
 }
 
+func Atoi(s string) (i int) {
+	i, _ = strconv.Atoi(s)
+	return
+}
+
 func Assert(ok bool) {
 	if !ok {
 		_, file, line, _ := runtime.Caller(1)