优化代码，新增文件判断

job/job.go

@@ -111,7 +111,7 @@ func transcoder(svcCtx *svc.ServiceContext, req *types.CallbackRequest) (resp *t
 	var isAudio bool
 	mtype, _ := mimetype.DetectReader(silkFile)
 	if mtype.Is("application/octet-stream") {
-		var buf = make([]byte, 5)
+		var buf = make([]byte, 10)
 		if _, err = silkFile.Read(buf); err == nil {
 			if bytes.Equal(buf, []byte{2, 35, 33, 83, 73, 76, 75, 95, 86, 51}) {
 				isAudio = true