diff --git a/av/avutil/avutil.go b/av/avutil/avutil.go
index 31b4b1c..78bd741 100644
--- a/av/avutil/avutil.go
+++ b/av/avutil/avutil.go
@@ -127,7 +127,7 @@ func (self *Handlers) NewAudioDecoder(codec av.AudioCodecData) (dec av.AudioDeco
 }
 
 func (self *Handlers) Open(uri string) (demuxer av.DemuxCloser, err error) {
-	util.PrintCallTrace(1)
+	util.PrintCallTrace(1, "Handlers.Open")
 
 	listen := false
 	if strings.HasPrefix(uri, "listen:") {
@@ -135,6 +135,8 @@ func (self *Handlers) Open(uri string) (demuxer av.DemuxCloser, err error) {
 		listen = true
 	}
 
+	util.PrintCallTrace(1, "Handlers.Open")
+
 	for _, handler := range self.handlers {
 		if listen {
 			if handler.ServerDemuxer != nil {
@@ -272,8 +274,7 @@ func (self *Handlers) FindCreate(uri string) (handler RegisterHandler, muxer av.
 var DefaultHandlers = &Handlers{}
 
 func Open(url string) (demuxer av.DemuxCloser, err error) {
-	fmt.Println("avutil Open!")
-	util.PrintCallTrace(1)
+	util.PrintCallTrace(1, "avutil Open!")
 	return DefaultHandlers.Open(url)
 }
 
diff --git a/util/util.go b/util/util.go
index ef7e19b..ea29c71 100644
--- a/util/util.go
+++ b/util/util.go
@@ -5,9 +5,9 @@ import (
 	"runtime"
 )
 
-func PrintCallTrace(depth int) {
+func PrintCallTrace(depth int, v interface{}) {
 	funcname, file, line, ok := runtime.Caller(depth)
 	if ok {
-		fmt.Printf("[%s:%d %s]\n", file, line, runtime.FuncForPC(funcname).Name())
+		fmt.Printf("[%s:%d %s] %v\n", file, line, runtime.FuncForPC(funcname).Name(), v)
 	}
 }