Tidy up and increase exception handling in compare_videos

Bug: webrtc:9642
Change-Id: I5c8b252de3b285f81a5437af99d789b5a28ce646
Reviewed-on: https://webrtc-review.googlesource.com/102880
Commit-Queue: Paulina Hensman <phensman@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24909}
diff --git a/rtc_tools/frame_analyzer/frame_analyzer.cc b/rtc_tools/frame_analyzer/frame_analyzer.cc
index 56dc1f4..78c1929 100644
--- a/rtc_tools/frame_analyzer/frame_analyzer.cc
+++ b/rtc_tools/frame_analyzer/frame_analyzer.cc
@@ -21,6 +21,7 @@
 #include "rtc_tools/simple_command_line_parser.h"
 #include "rtc_tools/video_file_reader.h"
 #include "rtc_tools/video_file_writer.h"
+#include "test/testsupport/fileutils.h"
 #include "test/testsupport/perf_test.h"
 
 /*
@@ -147,10 +148,12 @@
   }
   std::string yuv_directory = parser.GetFlag("yuv_directory");
   if (!yuv_directory.empty()) {
-    webrtc::test::WriteVideoToFile(reordered_video, yuv_directory + "ref.yuv",
-                                   /*fps=*/30);
-    webrtc::test::WriteVideoToFile(test_video, yuv_directory + "test.yuv",
-                                   /*fps=*/30);
+    webrtc::test::WriteVideoToFile(
+        reordered_video, webrtc::test::JoinFilename(yuv_directory, "ref.yuv"),
+        /*fps=*/30);
+    webrtc::test::WriteVideoToFile(
+        test_video, webrtc::test::JoinFilename(yuv_directory, "test.yuv"),
+        /*fps=*/30);
   }
 
   return 0;