diff --git a/src/audiosource.cpp b/src/audiosource.cpp
index 5792929..e560322 100644
--- a/src/audiosource.cpp
+++ b/src/audiosource.cpp
@@ -384,7 +384,8 @@ BestAudioSource::BestAudioSource(const std::string &SourceFile, int Track, int A
 
     Decoder->GetAudioProperties(AP);
     AudioTrack = Decoder->GetTrack();
-    
+    FileSize = Decoder->GetSourceSize();
+
     if (!ReadAudioTrackIndex(CachePath.empty() ? SourceFile : CachePath)) {
         if (!IndexTrack(Progress))
             throw BestSourceException("Indexing of '" + SourceFile + "' track #" + std::to_string(AudioTrack) + " failed");
@@ -1115,7 +1116,7 @@ bool BestAudioSource::ReadAudioTrackIndex(const std::string &CachePath) {
         return false;
     if (!ReadBSHeader(F, false))
         return false;
-    if (!ReadCompareInt64(F, GetFileSize(Source)))
+    if (!ReadCompareInt64(F, FileSize))
         return false;
     if (!ReadCompareInt(F, AudioTrack))
         return false;
diff --git a/src/audiosource.h b/src/audiosource.h
index 08bcbf4..2f2dff0 100644
--- a/src/audiosource.h
+++ b/src/audiosource.h
@@ -158,6 +158,7 @@ class BestAudioSource {
     std::unique_ptr<LWAudioDecoder> Decoders[MaxVideoSources];
     int64_t PreRoll = 40;
     int64_t SampleDelay = 0;
+    int64_t FileSize = -1;
     static constexpr size_t RetrySeekAttempts = 10;
     std::set<int64_t> BadSeekLocations;
     void SetLinearMode();
diff --git a/src/bsshared.cpp b/src/bsshared.cpp
index 1052036..00747e5 100644
--- a/src/bsshared.cpp
+++ b/src/bsshared.cpp
@@ -82,19 +82,6 @@ file_ptr_t OpenFile(const std::string &Filename, bool Write) {
     return F;
 }
 
-int64_t GetFileSize(const std::string &Filename) {
-    file_ptr_t F = OpenFile(Filename, false);
-#ifdef _WIN32
-    if (fseek(F.get(), 0, SEEK_END) != 0)
-        return -1;
-    return _ftelli64(F.get());
-#else
-    if (fseeko(F.get(), 0, SEEK_END) != 0)
-        return -1;
-    return ftello(F.get());
-#endif
-}
-
 file_ptr_t OpenCacheFile(const std::string &CachePath, int Track, bool Write) {
     return OpenFile(CachePath + "." + std::to_string(Track) + ".bsindex", Write);
 }
diff --git a/src/bsshared.h b/src/bsshared.h
index 4077dd8..85244b1 100644
--- a/src/bsshared.h
+++ b/src/bsshared.h
@@ -62,7 +62,6 @@ void SetBSDebugOutput(bool DebugOutput);
 void BSDebugPrint(const std::string_view Message, int64_t RequestedN = -1, int64_t CurrentN = -1);
 
 file_ptr_t OpenFile(const std::string &Filename, bool Write);
-int64_t GetFileSize(const std::string &Filename);
 file_ptr_t OpenCacheFile(const std::string &CachePath, int Track, bool Write);
 void WriteByte(file_ptr_t &F, uint8_t Value);
 void WriteInt(file_ptr_t &F, int Value);
diff --git a/src/version.h b/src/version.h
index 5a5957d..a7e61b5 100644
--- a/src/version.h
+++ b/src/version.h
@@ -22,6 +22,6 @@
 #define VERSION_H
 
 #define BEST_SOURCE_VERSION_MAJOR 2
-#define BEST_SOURCE_VERSION_MINOR 97
+#define BEST_SOURCE_VERSION_MINOR -21
 
 #endif
\ No newline at end of file
diff --git a/src/videosource.cpp b/src/videosource.cpp
index 4c6af5c..f0fe0d4 100644
--- a/src/videosource.cpp
+++ b/src/videosource.cpp
@@ -787,6 +787,7 @@ BestVideoSource::BestVideoSource(const std::string &SourceFile, const std::strin
 
     Decoder->GetVideoProperties(VP);
     VideoTrack = Decoder->GetTrack();
+    FileSize = Decoder->GetSourceSize();
     
     if (!ReadVideoTrackIndex(CachePath.empty() ? SourceFile : CachePath)) {
         if (!IndexTrack(Progress))
@@ -1306,7 +1307,7 @@ bool BestVideoSource::WriteVideoTrackIndex(const std::string &CachePath) {
     if (!F)
         return false;
     WriteBSHeader(F, true);
-    WriteInt64(F, GetFileSize(Source));
+    WriteInt64(F, FileSize);
     WriteInt(F, VideoTrack);
     WriteInt(F, VariableFormat);
     WriteString(F, HWDevice);
@@ -1383,7 +1384,7 @@ bool BestVideoSource::ReadVideoTrackIndex(const std::string &CachePath) {
         return false;
     if (!ReadBSHeader(F, true))
         return false;
-    if (!ReadCompareInt64(F, GetFileSize(Source)))
+    if (!ReadCompareInt64(F, FileSize))
         return false;
     if (!ReadCompareInt(F, VideoTrack))
         return false;
diff --git a/src/videosource.h b/src/videosource.h
index 57f4ca4..a1883b1 100644
--- a/src/videosource.h
+++ b/src/videosource.h
@@ -240,6 +240,7 @@ class BestVideoSource {
     uint64_t DecoderLastUse[MaxVideoSources] = {};
     std::unique_ptr<LWVideoDecoder> Decoders[MaxVideoSources];
     int64_t PreRoll = 20;
+    int64_t FileSize = -1;
     static constexpr size_t RetrySeekAttempts = 10;
     std::set<int64_t> BadSeekLocations;
     void SetLinearMode();