diff --git a/app/codec/decoder.cpp b/app/codec/decoder.cpp
index 9da151b7c..0eebf8055 100644
--- a/app/codec/decoder.cpp
+++ b/app/codec/decoder.cpp
@@ -335,7 +335,7 @@ void Decoder::UpdateLastAccessed()
 
 uint qHash(Decoder::CodecStream stream, uint seed)
 {
-  return qHash(stream.filename(), seed) ^ qHash(stream.stream(), seed);
+  return qHash(stream.filename(), seed) ^ qHash(stream.stream(), seed) ^ qHash(stream.block(), seed);
 }
 
 }
diff --git a/app/codec/decoder.h b/app/codec/decoder.h
index 061378be0..99fa74428 100644
--- a/app/codec/decoder.h
+++ b/app/codec/decoder.h
@@ -34,6 +34,7 @@ extern "C" {
 #include "codec/frame.h"
 #include "codec/samplebuffer.h"
 #include "common/rational.h"
+#include "node/block/block.h"
 #include "node/project/footage/footage.h"
 #include "node/project/footage/footagedescription.h"
 #include "task/task.h"
@@ -85,13 +86,15 @@ public:
   {
   public:
     CodecStream() :
-      stream_(-1)
+      stream_(-1),
+      block_(nullptr)
     {
     }
 
-    CodecStream(const QString& filename, int stream) :
+    CodecStream(const QString& filename, int stream, Block *block) :
       filename_(filename),
-      stream_(stream)
+      stream_(stream),
+      block_(block)
     {
     }
 
@@ -125,11 +128,18 @@ public:
       return stream_;
     }
 
+    Block *block() const
+    {
+      return block_;
+    }
+
   private:
     QString filename_;
 
     int stream_;
 
+    Block *block_;
+
   };
 
   /**
diff --git a/app/codec/ffmpeg/ffmpegdecoder.cpp b/app/codec/ffmpeg/ffmpegdecoder.cpp
index 96d69df9b..b963306ff 100644
--- a/app/codec/ffmpeg/ffmpegdecoder.cpp
+++ b/app/codec/ffmpeg/ffmpegdecoder.cpp
@@ -62,7 +62,6 @@ FFmpegDecoder::FFmpegDecoder() :
   native_output_pix_fmt_(VideoParams::kFormatInvalid),
   working_frame_(nullptr),
   working_packet_(nullptr),
-  is_working_(false),
   cache_at_zero_(false),
   cache_at_eof_(false)
 {
@@ -749,7 +748,7 @@ AVFramePtr FFmpegDecoder::RetrieveFrame(const rational& time, const QAtomicInt *
   int64_t target_ts = GetTimeInTimebaseUnits(time, instance_.avstream()->time_base, instance_.avstream()->start_time);
 
   const int64_t min_seek = -instance_.avstream()->start_time;
-  int64_t seek_ts = target_ts;
+  int64_t seek_ts = std::max(min_seek, target_ts - MaximumQueueSize());
   bool still_seeking = false;
 
   if (time != kAnyTimecode) {
@@ -838,7 +837,7 @@ AVFramePtr FFmpegDecoder::RetrieveFrame(const rational& time, const QAtomicInt *
     } else {
 
       // Cut down to thread count - 1 before we acquire a new frame
-      if (cached_frames_.size() == size_t(QThread::idealThreadCount())) {
+      if (cached_frames_.size() == size_t(MaximumQueueSize())) {
         RemoveFirstFrame();
       }
 
@@ -1039,6 +1038,11 @@ void FFmpegDecoder::RemoveFirstFrame()
   cache_at_zero_ = false;
 }
 
+int FFmpegDecoder::MaximumQueueSize()
+{
+  return QThread::idealThreadCount();
+}
+
 FFmpegDecoder::Instance::Instance() :
   fmt_ctx_(nullptr),
   codec_ctx_(nullptr),
diff --git a/app/codec/ffmpeg/ffmpegdecoder.h b/app/codec/ffmpeg/ffmpegdecoder.h
index 80c46fb1f..4e51f496f 100644
--- a/app/codec/ffmpeg/ffmpegdecoder.h
+++ b/app/codec/ffmpeg/ffmpegdecoder.h
@@ -155,6 +155,8 @@ private:
 
   void RemoveFirstFrame();
 
+  static int MaximumQueueSize();
+
   RetrieveVideoParams filter_params_;
   AVFilterGraph* filter_graph_;
   AVFilterContext* buffersrc_ctx_;
@@ -171,9 +173,6 @@ private:
 
   std::list<AVFramePtr> cached_frames_;
 
-  bool is_working_;
-  QMutex is_working_mutex_;
-
   bool cache_at_zero_;
   bool cache_at_eof_;
 
diff --git a/app/node/traverser.cpp b/app/node/traverser.cpp
index da04f5e99..ca4267d52 100644
--- a/app/node/traverser.cpp
+++ b/app/node/traverser.cpp
@@ -350,7 +350,9 @@ NodeValueTable NodeTraverser::GenerateBlockTable(const Track *track, const TimeR
   NodeValueTable table;
 
   if (active_block) {
+    block_stack_.push_back(active_block);
     table = GenerateTable(active_block, Track::TransformRangeForBlock(active_block, range), track);
+    block_stack_.pop_back();
   }
 
   return table;
diff --git a/app/node/traverser.h b/app/node/traverser.h
index fca5083f3..105955450 100644
--- a/app/node/traverser.h
+++ b/app/node/traverser.h
@@ -146,6 +146,11 @@ protected:
 
   void ResolveJobs(NodeValue &value, const TimeRange &range);
 
+  Block *GetCurrentBlock() const
+  {
+    return block_stack_.empty() ? nullptr : block_stack_.back();
+  }
+
 private:
   void PreProcessRow(const TimeRange &range, NodeValueRow &row);
 
@@ -162,6 +167,8 @@ private:
   const Node *transform_now_;
   QTransform *transform_;
 
+  std::list<Block*> block_stack_;
+
 };
 
 }
diff --git a/app/render/rendercache.h b/app/render/rendercache.h
index 114244fb8..77a56780d 100644
--- a/app/render/rendercache.h
+++ b/app/render/rendercache.h
@@ -39,15 +39,10 @@ private:
 
 };
 
-struct DecoderPair {
-  DecoderPair()
-  {
-    decoder = nullptr;
-    last_modified = 0;
-  }
-
-  DecoderPtr decoder;
-  qint64 last_modified;
+struct DecoderPair
+{
+  DecoderPtr decoder = nullptr;
+  qint64 last_modified = 0;
 };
 
 using DecoderCache = RenderCache<Decoder::CodecStream, DecoderPair>;
diff --git a/app/render/renderer.cpp b/app/render/renderer.cpp
index 80683c285..b66fd6ca8 100644
--- a/app/render/renderer.cpp
+++ b/app/render/renderer.cpp
@@ -72,8 +72,21 @@ TexturePtr Renderer::InterlaceTexture(TexturePtr top, TexturePtr bottom, const V
   return output;
 }
 
+QVariant Renderer::GetDefaultShader()
+{
+  if (default_shader_.isNull()) {
+    default_shader_ = CreateNativeShader(ShaderCode(QString(), QString()));
+  }
+
+  return default_shader_;
+}
+
 void Renderer::Destroy()
 {
+  if (!default_shader_.isNull()) {
+    DestroyNativeShader(default_shader_);
+  }
+
   color_cache_.clear();
 
   if (!interlace_texture_.isNull()) {
diff --git a/app/render/renderer.h b/app/render/renderer.h
index 749d777cf..839be32cf 100644
--- a/app/render/renderer.h
+++ b/app/render/renderer.h
@@ -76,6 +76,8 @@ public:
 
   TexturePtr InterlaceTexture(TexturePtr top, TexturePtr bottom, const VideoParams &params);
 
+  QVariant GetDefaultShader();
+
   void Destroy();
 
   virtual void PostDestroy() = 0;
@@ -134,6 +136,8 @@ private:
 
   QMutex color_cache_mutex_;
 
+  QVariant default_shader_;
+
   QVariant interlace_texture_;
 
 };
diff --git a/app/render/rendermanager.cpp b/app/render/rendermanager.cpp
index b86cc64ea..56ea08345 100644
--- a/app/render/rendermanager.cpp
+++ b/app/render/rendermanager.cpp
@@ -54,7 +54,6 @@ RenderManager::RenderManager(QObject *parent) :
 
     decoder_cache_ = new DecoderCache();
     shader_cache_ = new ShaderCache();
-    default_shader_ = context_->CreateNativeShader(ShaderCode(QString(), QString()));
   } else {
     qCritical() << "Tried to initialize unknown graphics backend";
     context_ = nullptr;
@@ -65,8 +64,6 @@ RenderManager::RenderManager(QObject *parent) :
 RenderManager::~RenderManager()
 {
   if (context_) {
-    context_->DestroyNativeShader(default_shader_);
-
     delete shader_cache_;
     delete decoder_cache_;
 
@@ -130,7 +127,7 @@ void RenderManager::RunTicket(RenderTicketPtr ticket) const
     return;
   }
 
-  RenderProcessor::Process(ticket, context_, decoder_cache_, shader_cache_, default_shader_);
+  RenderProcessor::Process(ticket, context_, decoder_cache_, shader_cache_);
 }
 
 }
diff --git a/app/render/rendermanager.h b/app/render/rendermanager.h
index 6bbe3ba17..1059ecd9e 100644
--- a/app/render/rendermanager.h
+++ b/app/render/rendermanager.h
@@ -183,8 +183,6 @@ private:
 
   ShaderCache* shader_cache_;
 
-  QVariant default_shader_;
-
 };
 
 }
diff --git a/app/render/renderprocessor.cpp b/app/render/renderprocessor.cpp
index 5a90b9e89..e89f3bbc6 100644
--- a/app/render/renderprocessor.cpp
+++ b/app/render/renderprocessor.cpp
@@ -35,12 +35,11 @@ namespace olive {
 
 #define super NodeTraverser
 
-RenderProcessor::RenderProcessor(RenderTicketPtr ticket, Renderer *render_ctx, DecoderCache* decoder_cache, ShaderCache *shader_cache, QVariant default_shader) :
+RenderProcessor::RenderProcessor(RenderTicketPtr ticket, Renderer *render_ctx, DecoderCache* decoder_cache, ShaderCache *shader_cache) :
   ticket_(ticket),
   render_ctx_(render_ctx),
   decoder_cache_(decoder_cache),
-  shader_cache_(shader_cache),
-  default_shader_(default_shader)
+  shader_cache_(shader_cache)
 {
 }
 
@@ -116,7 +115,7 @@ FramePtr RenderProcessor::GenerateFrame(TexturePtr texture, const rational& time
       job.Insert(QStringLiteral("ove_maintex"), NodeValue(NodeValue::kTexture, QVariant::fromValue(texture)));
       job.Insert(QStringLiteral("ove_mvpmat"), NodeValue(NodeValue::kMatrix, matrix));
 
-      render_ctx_->BlitToTexture(default_shader_, job, blit_tex.get());
+      render_ctx_->BlitToTexture(render_ctx_->GetDefaultShader(), job, blit_tex.get());
 
       // Replace texture that we're going to download in the next step
       texture = blit_tex;
@@ -258,10 +257,10 @@ DecoderPtr RenderProcessor::ResolveDecoderFromInput(const QString& decoder_id, c
     // No decoder
     decoder.decoder = Decoder::CreateFromID(decoder_id);
     decoder.last_modified = file_last_modified;
+    decoder_cache_->insert(stream, decoder);
+    locker.unlock();
 
-    if (decoder.decoder->Open(stream)) {
-      decoder_cache_->insert(stream, decoder);
-    } else {
+    if (!decoder.decoder->Open(stream)) {
       qWarning() << "Failed to open decoder for" << stream.filename()
                  << "::" << stream.stream();
       return nullptr;
@@ -271,9 +270,9 @@ DecoderPtr RenderProcessor::ResolveDecoderFromInput(const QString& decoder_id, c
   return decoder.decoder;
 }
 
-void RenderProcessor::Process(RenderTicketPtr ticket, Renderer *render_ctx, DecoderCache *decoder_cache, ShaderCache *shader_cache, QVariant default_shader)
+void RenderProcessor::Process(RenderTicketPtr ticket, Renderer *render_ctx, DecoderCache *decoder_cache, ShaderCache *shader_cache)
 {
-  RenderProcessor p(ticket, render_ctx, decoder_cache, shader_cache, default_shader);
+  RenderProcessor p(ticket, render_ctx, decoder_cache, shader_cache);
   p.Run();
 }
 
@@ -404,7 +403,7 @@ void RenderProcessor::ProcessVideoFootage(TexturePtr destination, const FootageJ
     qWarning() << "HAVEN'T GOTTEN DEFAULT INPUT COLORSPACE";
   }
 
-  Decoder::CodecStream default_codec_stream(stream.filename(), stream_data.stream_index());
+  Decoder::CodecStream default_codec_stream(stream.filename(), stream_data.stream_index(), GetCurrentBlock());
 
   QString decoder_id = stream.decoder();
 
@@ -426,7 +425,7 @@ void RenderProcessor::ProcessVideoFootage(TexturePtr destination, const FootageJ
     frame_filename = Decoder::TransformImageSequenceFileName(stream.filename(), frame_number);
 
     // Decoder will close automatically since it's a stream_ptr
-    decoder->Open(Decoder::CodecStream(frame_filename, stream_data.stream_index()));
+    decoder->Open(Decoder::CodecStream(frame_filename, stream_data.stream_index(), GetCurrentBlock()));
     break;
   }
   }
@@ -472,7 +471,7 @@ void RenderProcessor::ProcessVideoFootage(TexturePtr destination, const FootageJ
 
 void RenderProcessor::ProcessAudioFootage(SampleBuffer &destination, const FootageJob &stream, const TimeRange &input_time)
 {
-  DecoderPtr decoder = ResolveDecoderFromInput(stream.decoder(), Decoder::CodecStream(stream.filename(), stream.audio_params().stream_index()));
+  DecoderPtr decoder = ResolveDecoderFromInput(stream.decoder(), Decoder::CodecStream(stream.filename(), stream.audio_params().stream_index(), nullptr));
 
   if (decoder) {
     const AudioParams& audio_params = GetCacheAudioParams();
diff --git a/app/render/renderprocessor.h b/app/render/renderprocessor.h
index 9c0ad40cd..db147bd3e 100644
--- a/app/render/renderprocessor.h
+++ b/app/render/renderprocessor.h
@@ -32,7 +32,7 @@ namespace olive {
 class RenderProcessor : public NodeTraverser
 {
 public:
-  static void Process(RenderTicketPtr ticket, Renderer* render_ctx, DecoderCache* decoder_cache, ShaderCache* shader_cache, QVariant default_shader);
+  static void Process(RenderTicketPtr ticket, Renderer* render_ctx, DecoderCache* decoder_cache, ShaderCache* shader_cache);
 
   struct RenderedWaveform {
     const ClipBlock* block;
@@ -69,7 +69,7 @@ protected:
   virtual void ConvertToReferenceSpace(TexturePtr destination, TexturePtr source, const QString &input_cs) override;
 
 private:
-  RenderProcessor(RenderTicketPtr ticket, Renderer* render_ctx, DecoderCache* decoder_cache, ShaderCache* shader_cache, QVariant default_shader);
+  RenderProcessor(RenderTicketPtr ticket, Renderer* render_ctx, DecoderCache* decoder_cache, ShaderCache* shader_cache);
 
   TexturePtr GenerateTexture(const rational& time, const rational& frame_length);
 
@@ -87,8 +87,6 @@ private:
 
   ShaderCache* shader_cache_;
 
-  QVariant default_shader_;
-
 };
 
 }
diff --git a/app/threading/threadpool.cpp b/app/threading/threadpool.cpp
index b048f3519..8b33d72db 100644
--- a/app/threading/threadpool.cpp
+++ b/app/threading/threadpool.cpp
@@ -29,52 +29,67 @@ ThreadPool::ThreadPool(unsigned threads, QObject *parent) :
     threads = std::thread::hardware_concurrency();
   }
 
+  available_count_ = threads;
   for (unsigned i = 0; i < threads; i += 1) {
-    worker_threads_.emplace_back(std::bind(&ThreadPool::thread_exec, this));
+    worker_threads_.emplace_back(std::bind(&ThreadPool::thread_exec, this, &tasks_, &task_mutex_, &cond_));
   }
+
+  // Make single reserved thread for high priority tasks (usually audio) so they don't get stuck
+  // behind a lot of slow tasks
+  high_thread_ = std::thread(std::thread(std::bind(&ThreadPool::thread_exec, this, &high_tasks_, &high_mutex_, &high_cond_)));
 }
 
 void ThreadPool::AddTicket(RenderTicketPtr ticket, RenderTicketPriority priority)
 {
-  std::lock_guard<std::mutex> lock(task_mutex_);
-
   if (priority == RenderTicketPriority::kHigh) {
-    tasks_.emplace_front(std::move(ticket));
+    std::lock_guard<std::mutex> lock(high_mutex_);
+    high_tasks_.emplace_back(std::move(ticket));
+    high_cond_.notify_one();
   } else {
+    std::lock_guard<std::mutex> lock(task_mutex_);
     tasks_.emplace_back(std::move(ticket));
+    cond_.notify_one();
   }
-
-  cond_.notify_one();
 }
 
 bool ThreadPool::RemoveTicket(RenderTicketPtr ticket)
 {
-  std::lock_guard<std::mutex> lock(task_mutex_);
-
-  const auto it = std::find(tasks_.begin(), tasks_.end(), ticket);
-  if (it == tasks_.end()) {
-    return false;
+  {
+    std::lock_guard<std::mutex> lock(task_mutex_);
+    const auto it = std::find(tasks_.begin(), tasks_.end(), ticket);
+    if (it != tasks_.end()) {
+      tasks_.erase(it);
+      return true;
+    }
   }
 
-  tasks_.erase(it);
-  return true;
+  {
+    std::lock_guard<std::mutex> lock(high_mutex_);
+    const auto it = std::find(high_tasks_.begin(), high_tasks_.end(), ticket);
+    if (it != high_tasks_.end()) {
+      high_tasks_.erase(it);
+      return true;
+    }
+  }
+
+  return false;
 }
 
-void ThreadPool::thread_exec()
+void ThreadPool::thread_exec(std::deque<TaskType> *queue, std::mutex *mutex, std::condition_variable *cond)
 {
   while (true) {
     TaskType task;
 
     {
-      std::unique_lock<std::mutex> lock(task_mutex_);
-      cond_.wait(lock, [this]{ return this->end_threadp_ || !this->tasks_.empty(); });
+      std::unique_lock<std::mutex> lock(*mutex);
+      cond->wait(lock, [this, queue]{ return this->end_threadp_ || !queue->empty(); });
 
-      if (this->end_threadp_ && this->tasks_.empty()) {
+      if (this->end_threadp_ && queue->empty()) {
         break;
       }
 
-      task = std::move(tasks_.front());
-      tasks_.pop_front();
+      task = std::move(queue->front());
+      queue->pop_front();
     }
 
     RunTicket(task);
@@ -85,10 +100,12 @@ ThreadPool::~ThreadPool()
 {
   end_threadp_ = true;
   cond_.notify_all();
+  high_cond_.notify_all();
 
   for (auto &e : worker_threads_) {
     e.join();
   }
+  high_thread_.join();
 }
 
 }
diff --git a/app/threading/threadpool.h b/app/threading/threadpool.h
index 3c3204bb1..3c1143f55 100644
--- a/app/threading/threadpool.h
+++ b/app/threading/threadpool.h
@@ -49,13 +49,20 @@ public:
   virtual ~ThreadPool() override;
 
 private:
-  void thread_exec();
+  void thread_exec(std::deque<TaskType> *queue, std::mutex *mutex, std::condition_variable *cond);
 
   std::vector<std::thread> worker_threads_;
   std::deque<TaskType> tasks_;
   std::mutex task_mutex_;
   std::condition_variable cond_;
+
+  std::thread high_thread_;
+  std::deque<TaskType> high_tasks_;
+  std::mutex high_mutex_;
+  std::condition_variable high_cond_;
+
   std::atomic_bool end_threadp_{false};
+  std::atomic_int available_count_;
 
 };
 
diff --git a/app/widget/viewer/viewer.cpp b/app/widget/viewer/viewer.cpp
index 89dbd4d37..3f83d5ae7 100644
--- a/app/widget/viewer/viewer.cpp
+++ b/app/widget/viewer/viewer.cpp
@@ -702,7 +702,10 @@ void ViewerWidget::UpdateTextureFromNode()
     connect(watcher, &RenderTicketWatcher::Finished, this, &ViewerWidget::RendererGeneratedFrame);
     nonqueue_watchers_.append(watcher);
 
-    watcher->SetTicket(GetFrame(time, RenderTicketPriority::kHigh));
+    // Clear queue because we want this frame more than any others
+    auto_cacher_->ClearSingleFrameRenders();
+
+    watcher->SetTicket(GetFrame(time, RenderTicketPriority::kNormal));
   } else {
     // There is definitely no frame here, we can immediately flip to showing nothing
     nonqueue_watchers_.clear();
@@ -753,7 +756,7 @@ void ViewerWidget::PlayInternal(int speed, bool in_to_out_only)
   playback_speed_ = speed;
   play_in_to_out_only_ = in_to_out_only;
 
-  playback_queue_next_frame_ = GetTimestamp();
+  playback_queue_next_frame_ = GetTimestamp() + playback_speed_;
 
   controls_->ShowPauseButton();
 
@@ -767,18 +770,10 @@ void ViewerWidget::PlayInternal(int speed, bool in_to_out_only)
       prequeuing_video_ = true;
       prequeue_count_ = 0;
 
-      // We "prioritize" the frames, which means they're pushed to the top of the render queue,
-      // we queue in reverse so that they're still queued in order
-
-      playback_queue_next_frame_ += playback_speed_ * prequeue_length_;
-      int64_t temp = playback_queue_next_frame_;
-
       for (int i=0; i<prequeue_length_; i++) {
-        playback_queue_next_frame_ -= playback_speed_;
-        RequestNextFrameForQueue(RenderTicketPriority::kHigh, false);
+        RequestNextFrameForQueue(RenderTicketPriority::kNormal, false);
+        playback_queue_next_frame_ += playback_speed_;
       }
-
-      playback_queue_next_frame_ = temp;
     }
   }
 
@@ -1484,10 +1479,11 @@ void ViewerWidget::PlaybackTimerUpdate()
   }
 
   if (IsPlaying()) {
-    int count = 0;
-    for (int i=display_widget_->queue()->size(); i<DeterminePlaybackQueueSize(); i++) {
-      RequestNextFrameForQueue();
-      count++;
+    while (queue_watchers_.size() < DeterminePlaybackQueueSize()) {
+      if (!RequestNextFrameForQueue()) {
+        // Prevent infinite loop
+        break;
+      }
     }
   }