diff --git a/app/render/audioplaybackcache.cpp b/app/render/audioplaybackcache.cpp
index dc69b88c3..3a1d69611 100644
--- a/app/render/audioplaybackcache.cpp
+++ b/app/render/audioplaybackcache.cpp
@@ -39,6 +39,8 @@ AudioPlaybackCache::AudioPlaybackCache()
 
 void AudioPlaybackCache::SetParameters(const AudioRenderingParams &params)
 {
+  QMutexLocker locker(lock());
+
   if (params_ == params) {
     return;
   }
@@ -52,13 +54,19 @@ void AudioPlaybackCache::SetParameters(const AudioRenderingParams &params)
   }
 
   // Our current audio cache is unusable, so we truncate it automatically
-  InvalidateAll();
+  TimeRange invalidate_range(0, NoLockGetLength());
+  NoLockInvalidate(invalidate_range);
+
+  locker.unlock();
 
   emit ParametersChanged();
+  emit Invalidated(invalidate_range);
 }
 
 void AudioPlaybackCache::WritePCM(const TimeRange &range, SampleBufferPtr samples)
 {
+  QMutexLocker locker(lock());
+
   QFile f(filename_);
   if (f.open(QFile::ReadWrite)) {
     qint64 start_offset = params_.time_to_bytes(range.in());
@@ -82,7 +90,11 @@ void AudioPlaybackCache::WritePCM(const TimeRange &range, SampleBufferPtr sample
 
     f.close();
 
-    Validate(range);
+    NoLockValidate(range);
+
+    locker.unlock();
+
+    emit Validated(range);
   } else {
     qWarning() << "Failed to write PCM data to" << filename_;
   }
@@ -90,6 +102,8 @@ void AudioPlaybackCache::WritePCM(const TimeRange &range, SampleBufferPtr sample
 
 void AudioPlaybackCache::WriteSilence(const TimeRange &range)
 {
+  QMutexLocker locker(lock());
+
   QFile f(filename_);
   if (f.open(QFile::ReadWrite)) {
     qint64 start_offset = params_.time_to_bytes(range.in());
diff --git a/app/render/audioplaybackcache.h b/app/render/audioplaybackcache.h
index 1f7a97217..e3c01d5ec 100644
--- a/app/render/audioplaybackcache.h
+++ b/app/render/audioplaybackcache.h
@@ -33,7 +33,8 @@ class AudioPlaybackCache : public PlaybackCache
 public:
   AudioPlaybackCache();
 
-  const AudioRenderingParams& GetParameters() const {
+  AudioRenderingParams GetParameters() {
+    QMutexLocker locker(lock());
     return params_;
   }
 
diff --git a/app/render/framehashcache.cpp b/app/render/framehashcache.cpp
index c49378736..52b86bb26 100644
--- a/app/render/framehashcache.cpp
+++ b/app/render/framehashcache.cpp
@@ -34,25 +34,39 @@
 
 OLIVE_NAMESPACE_ENTER
 
-QByteArray FrameHashCache::GetHash(const rational &time) const
+QByteArray FrameHashCache::GetHash(const rational &time)
 {
+  QMutexLocker locker(lock());
+
   return time_hash_map_.value(time);
 }
 
 void FrameHashCache::SetHash(const rational &time, const QByteArray &hash)
 {
+  QMutexLocker locker(lock());
+
   time_hash_map_.insert(time, hash);
 
-  Validate(TimeRange(time, time + timebase_));
+  TimeRange validated_range(time, time + timebase_);
+
+  NoLockValidate(validated_range);
+
+  locker.unlock();
+
+  emit Validated(validated_range);
 }
 
 void FrameHashCache::SetTimebase(const rational &tb)
 {
+  QMutexLocker locker(lock());
+
   timebase_ = tb;
 }
 
-QList<rational> FrameHashCache::GetFramesWithHash(const QByteArray &hash) const
+QList<rational> FrameHashCache::GetFramesWithHash(const QByteArray &hash)
 {
+  QMutexLocker locker(lock());
+
   QList<rational> times;
 
   QMap<rational, QByteArray>::const_iterator iterator;
@@ -68,6 +82,8 @@ QList<rational> FrameHashCache::GetFramesWithHash(const QByteArray &hash) const
 
 QList<rational> FrameHashCache::TakeFramesWithHash(const QByteArray &hash)
 {
+  QMutexLocker locker(lock());
+
   QList<rational> times;
 
   QMap<rational, QByteArray>::iterator iterator = time_hash_map_.begin();
@@ -82,11 +98,23 @@ QList<rational> FrameHashCache::TakeFramesWithHash(const QByteArray &hash)
     }
   }
 
+  foreach (const rational& r, times) {
+    NoLockInvalidate(TimeRange(r, r + timebase_));
+  }
+
+  locker.unlock();
+
+  foreach (const rational& r, times) {
+    emit Invalidated(TimeRange(r, r + timebase_));
+  }
+
   return times;
 }
 
-const QMap<rational, QByteArray> &FrameHashCache::time_hash_map() const
+QMap<rational, QByteArray> FrameHashCache::time_hash_map()
 {
+  QMutexLocker locker(lock());
+
   return time_hash_map_;
 }
 
@@ -130,14 +158,18 @@ QList<rational> FrameHashCache::GetFrameListFromTimeRange(TimeRangeList range_li
   return times;
 }
 
-QList<rational> FrameHashCache::GetFrameListFromTimeRange(const TimeRangeList &range) const
+QList<rational> FrameHashCache::GetFrameListFromTimeRange(const TimeRangeList &range)
 {
+  QMutexLocker locker(lock());
+
   return GetFrameListFromTimeRange(range, timebase_);
 }
 
-QList<rational> FrameHashCache::GetInvalidatedFrames() const
+QList<rational> FrameHashCache::GetInvalidatedFrames()
 {
-  return GetFrameListFromTimeRange(GetInvalidatedRanges());
+  QMutexLocker locker(lock());
+
+  return GetFrameListFromTimeRange(NoLockGetInvalidatedRanges());
 }
 
 void FrameHashCache::SaveCacheFrame(const QByteArray& hash,
diff --git a/app/render/framehashcache.h b/app/render/framehashcache.h
index e87db2304..927437623 100644
--- a/app/render/framehashcache.h
+++ b/app/render/framehashcache.h
@@ -37,7 +37,7 @@ class FrameHashCache : public PlaybackCache
 public:
   FrameHashCache() = default;
 
-  QByteArray GetHash(const rational& time) const;
+  QByteArray GetHash(const rational& time);
 
   void SetHash(const rational& time, const QByteArray& hash);
 
@@ -46,14 +46,14 @@ public:
   /**
    * @brief Returns a list of frames that use a particular hash
    */
-  QList<rational> GetFramesWithHash(const QByteArray& hash) const;
+  QList<rational> GetFramesWithHash(const QByteArray& hash);
 
   /**
    * @brief Same as FramesWithHash() but also removes these frames from the map
    */
   QList<rational> TakeFramesWithHash(const QByteArray& hash);
 
-  const QMap<rational, QByteArray>& time_hash_map() const;
+  QMap<rational, QByteArray> time_hash_map();
 
   /**
    * @brief Return the path of the cached image at this time
@@ -67,8 +67,8 @@ public:
   static QString GetFormatExtension(const PixelFormat::Format& f);
 
   static QList<rational> GetFrameListFromTimeRange(TimeRangeList range_list, const rational& timebase);
-  QList<rational> GetFrameListFromTimeRange(const TimeRangeList &range) const;
-  QList<rational> GetInvalidatedFrames() const;
+  QList<rational> GetFrameListFromTimeRange(const TimeRangeList &range);
+  QList<rational> GetInvalidatedFrames();
 
 protected:
   virtual void LengthChangedEvent(const rational& old, const rational& newlen) override;
diff --git a/app/render/playbackcache.cpp b/app/render/playbackcache.cpp
index 2ef2b1e87..0a826fc54 100644
--- a/app/render/playbackcache.cpp
+++ b/app/render/playbackcache.cpp
@@ -22,21 +22,93 @@
 
 OLIVE_NAMESPACE_ENTER
 
-PlaybackCache::PlaybackCache()
-{
-
-}
-
 void PlaybackCache::Invalidate(const TimeRange &r)
 {
-  invalidated_.InsertTimeRange(r);
+  QMutexLocker locker(&lock_);
 
-  InvalidateEvent(r);
+  NoLockInvalidate(r);
+
+  locker.unlock();
 
   emit Invalidated(r);
 }
 
+void PlaybackCache::InvalidateAll()
+{
+  QMutexLocker locker(&lock_);
+
+  TimeRange invalidate_range(0, length_);
+
+  NoLockInvalidate(invalidate_range);
+
+  locker.unlock();
+
+  emit Invalidated(invalidate_range);
+}
+
 void PlaybackCache::SetLength(const rational &r)
+{
+  QMutexLocker locker(&lock_);
+
+  NoLockSetLength(r);
+}
+
+void PlaybackCache::Shift(const rational &from, const rational &to)
+{
+  QMutexLocker locker(&lock_);
+
+  // An region between `from` and `to` will be inserted or spliced out
+  TimeRangeList ranges_to_shift = invalidated_.Intersects(TimeRange(from, RATIONAL_MAX));
+
+  // Remove everything from the minimum point
+  invalidated_.RemoveTimeRange(TimeRange(qMin(from, to), RATIONAL_MAX));
+
+  // Shift everything in our ranges to shift list
+  //
+  // `diff` is POSITIVE when moving forward -> and NEGATIVE when moving backward <-
+  rational diff = to - from;
+  foreach (const TimeRange& r, ranges_to_shift) {
+    invalidated_.InsertTimeRange(r + diff);
+  }
+
+  ShiftEvent(from, to);
+
+  if (diff > rational()) {
+    // If shifting forward, add this section to the invalidated region
+    TimeRange invalidate_range(from, to);
+
+    NoLockInvalidate(invalidate_range);
+
+    locker.unlock();
+
+    emit Invalidated(invalidate_range);
+  }
+}
+
+void PlaybackCache::Validate(const TimeRange &r)
+{
+  QMutexLocker locker(&lock_);
+
+  NoLockValidate(r);
+
+  locker.unlock();
+
+  emit Validated(r);
+}
+
+void PlaybackCache::NoLockInvalidate(const TimeRange &r)
+{
+  invalidated_.InsertTimeRange(r);
+
+  InvalidateEvent(r);
+}
+
+void PlaybackCache::NoLockValidate(const TimeRange &r)
+{
+  invalidated_.RemoveTimeRange(r);
+}
+
+void PlaybackCache::NoLockSetLength(const rational &r)
 {
   if (length_ == r) {
     // Same length - do nothing
@@ -56,47 +128,6 @@ void PlaybackCache::SetLength(const rational &r)
   length_ = r;
 }
 
-bool PlaybackCache::IsFullyValidated() const
-{
-  return invalidated_.isEmpty();
-}
-
-void PlaybackCache::Shift(const rational &from, const rational &to)
-{
-  // An region between `from` and `to` will be inserted or spliced out
-  TimeRangeList ranges_to_shift = invalidated_.Intersects(TimeRange(from, RATIONAL_MAX));
-
-  // Remove everything from the minimum point
-  invalidated_.RemoveTimeRange(TimeRange(qMin(from, to), RATIONAL_MAX));
-
-  // Shift everything in our ranges to shift list
-  //
-  // `diff` is POSITIVE when moving forward -> and NEGATIVE when moving backward <-
-  rational diff = to - from;
-  foreach (const TimeRange& r, ranges_to_shift) {
-    invalidated_.InsertTimeRange(r + diff);
-  }
-
-  ShiftEvent(from, to);
-
-  if (diff > rational()) {
-    // If shifting forward, add this section to the invalidated region
-    Invalidate(TimeRange(from, to));
-  }
-}
-
-void PlaybackCache::Validate(const TimeRange &r)
-{
-  invalidated_.RemoveTimeRange(r);
-
-  emit Validated(r);
-}
-
-void PlaybackCache::InvalidateAll()
-{
-  Invalidate(TimeRange(0, length_));
-}
-
 void PlaybackCache::LengthChangedEvent(const rational &, const rational &)
 {
 }
diff --git a/app/render/playbackcache.h b/app/render/playbackcache.h
index 7e48d4283..566f5d6a6 100644
--- a/app/render/playbackcache.h
+++ b/app/render/playbackcache.h
@@ -21,6 +21,7 @@
 #ifndef PLAYBACKCACHE_H
 #define PLAYBACKCACHE_H
 
+#include <QMutex>
 #include <QObject>
 
 #include "common/timerange.h"
@@ -31,30 +32,41 @@ class PlaybackCache : public QObject
 {
   Q_OBJECT
 public:
-  PlaybackCache();
+  PlaybackCache() = default;
 
   void Invalidate(const TimeRange& r);
 
   void InvalidateAll();
 
-  const rational& GetLength() const
+  const rational& GetLength()
   {
-    return length_;
+    QMutexLocker locker(lock());
+
+    return NoLockGetLength();
   }
 
   void SetLength(const rational& r);
 
-  bool IsFullyValidated() const;
+  bool IsFullyValidated()
+  {
+    QMutexLocker locker(lock());
+
+    return invalidated_.isEmpty();
+  }
 
   void Shift(const rational& from, const rational& to);
 
-  const TimeRangeList& GetInvalidatedRanges() const
+  const TimeRangeList& GetInvalidatedRanges()
   {
-    return invalidated_;
+    QMutexLocker locker(lock());
+
+    return NoLockGetInvalidatedRanges();
   }
 
-  bool HasInvalidatedRanges() const
+  bool HasInvalidatedRanges()
   {
+    QMutexLocker locker(lock());
+
     return !invalidated_.isEmpty();
   }
 
@@ -68,13 +80,36 @@ signals:
 protected:
   void Validate(const TimeRange& r);
 
+  void NoLockInvalidate(const TimeRange& r);
+
+  void NoLockValidate(const TimeRange& r);
+
+  void NoLockSetLength(const rational& r);
+
+  const rational& NoLockGetLength() const
+  {
+    return length_;
+  }
+
+  const TimeRangeList& NoLockGetInvalidatedRanges()
+  {
+    return invalidated_;
+  }
+
   virtual void LengthChangedEvent(const rational& old, const rational& newlen);
 
   virtual void InvalidateEvent(const TimeRange& range);
 
   virtual void ShiftEvent(const rational& from, const rational& to);
 
+  QMutex* lock()
+  {
+    return &lock_;
+  }
+
 private:
+  QMutex lock_;
+
   TimeRangeList invalidated_;
 
   rational length_;