diff --git a/ffprobe/extensions.go b/ffprobe/extensions.go
index 0c8ecd1..560b031 100644
--- a/ffprobe/extensions.go
+++ b/ffprobe/extensions.go
@@ -39,13 +39,13 @@ func (p *Probe) GetResolution() (width int, height int) {
 }
 
 func (p *Probe) GetStreamDuration(codecType ...string) (float64, error) {
-	selected := 'video'
-	if len(codecTypes) > 0{
-		selected = codecType[0]
+	selectedCodec := "video"
+	if len(codecType) > 0 {
+		selectedCodec = codecType[0]
 	}
 	var selected Stream
 	for _, stream := range p.Streams {
-		if stream.CodecType == codecType {
+		if stream.CodecType == selectedCodec {
 			selected = stream
 			break
 		}