diff --git a/src/audiosource.cpp b/src/audiosource.cpp
index 819ce20..8032d98 100644
--- a/src/audiosource.cpp
+++ b/src/audiosource.cpp
@@ -980,6 +980,9 @@ bool BestAudioSource::FillInFramePlanar(const BestAudioFrame *Frame, int64_t Fra
 }
 
 void BestAudioSource::GetPackedAudio(uint8_t *Data, int64_t Start, int64_t Count) {
+    if (VariableFormat)
+        throw BestSourceException("GetPackedAudio() can only be used when variable format is disabled");
+
     Start -= SampleDelay;
 
     ZeroFillStartPacked(Data, Start, Count);
@@ -1005,6 +1008,9 @@ void BestAudioSource::GetPackedAudio(uint8_t *Data, int64_t Start, int64_t Count
 }
 
 void BestAudioSource::GetPlanarAudio(uint8_t *const *const Data, int64_t Start, int64_t Count) {
+    if (VariableFormat)
+        throw BestSourceException("GetPlanarAudio() can only be used when variable format is disabled");
+
     Start -= SampleDelay;
 
     std::vector<uint8_t *> DataV;
diff --git a/src/audiosource.h b/src/audiosource.h
index a96148a..6ef0316 100644
--- a/src/audiosource.h
+++ b/src/audiosource.h
@@ -167,7 +167,6 @@ class BestAudioSource {
     [[nodiscard]] BestAudioFrame *GetFrameInternal(int64_t N);
     [[nodiscard]] BestAudioFrame *GetFrameLinearInternal(int64_t N, int64_t SeekFrame = -1, size_t Depth = 0, bool ForceUnseeked = false);
     [[nodiscard]] bool IndexTrack(const ProgressFunction &Progress = nullptr);
-    bool InitializeRFF();
     void ZeroFillStartPacked(uint8_t *&Data, int64_t &Start, int64_t &Count);
     void ZeroFillEndPacked(uint8_t *Data, int64_t Start, int64_t &Count);
     bool FillInFramePacked(const BestAudioFrame *Frame, int64_t FrameStartSample, uint8_t *&Data, int64_t &Start, int64_t &Count);