Fix preserve mtimes for Opus files

Author: complexlogic

src/scan.cpp

@@ -213,6 +213,10 @@ bool ScanJob::Track::scan(const Config &config, std::mutex *m)
     SwrContext *swr = nullptr;
     AVFormatContext *format_ctx = nullptr;
     const AVStream *stream = nullptr;
+    if (config.preserve_mtimes) {
+        mtime = std::make_unique<std::filesystem::file_time_type>();
+        *mtime = std::filesystem::last_write_time(path);
+    }
 
     // For Opus files, FFmpeg always adjusts the decoded audio samples by the header output
     // gain with no way to disable. To get the actual loudness of the audio signal,

src/scan.hpp

@@ -53,6 +53,7 @@ class ScanJob {
 			std::filesystem::path path;
 			FileType type;
 			std::unique_ptr<ebur128_state, decltype(&free_ebur128)> ebur128;
+			std::unique_ptr<std::filesystem::file_time_type> mtime;
 			std::string container;
 			ScanResult result;
 			int codec_id;

src/tag.cpp

@@ -168,10 +168,6 @@ static_assert((size_t) R128Tag::MAX_VAL == R128_STRING.size());
 
 void tag_track(ScanJob::Track &track, const Config &config)
 {
-    std::filesystem::file_time_type mtime;
-    if (config.preserve_mtimes)
-        mtime = std::filesystem::last_write_time(track.path);
-
     switch (track.type) {
         case FileType::MP2:
         case FileType::MP3:
@@ -257,8 +253,8 @@ void tag_track(ScanJob::Track &track, const Config &config)
         default:
             break;
     }
-    if (config.preserve_mtimes)
-        std::filesystem::last_write_time(track.path, mtime);
+    if (track.mtime)
+        std::filesystem::last_write_time(track.path, *(track.mtime));
 }
 
 bool tag_exists(const ScanJob::Track &track)