protocol/rtsp: doing RTSP and response length check in same if

protocol/rtsp/rtsp.go

@@ -41,7 +41,7 @@ import (
 )
 
 // Minimum response size to be considered valid in bytes.
-const minResponse = 2
+const minResponse = 12
 
 var errSmallResponse = errors.New("response too small")
 
@@ -132,12 +132,8 @@ func ReadResponse(r io.Reader) (*Response, error) {
 	}
 	s := scanner.Text()
 
-	if len(s) < minResponse {
-		return nil, errSmallResponse
-	}
-
-	if s[:5] != "RTSP/" {
-		return nil, errors.New("not a valid RTSP response")
+	if s[:5] != "RTSP/" || len(s) < minResponse {
+		return nil, errors.New("response not valid")
 	}
 	resp.Proto = "RTSP"