Implement flushing in VTVideoDecodeAccelerator.

content/common/gpu/media/vt_video_decode_accelerator.h

Index: content/common/gpu/media/vt_video_decode_accelerator.h
diff --git a/content/common/gpu/media/vt_video_decode_accelerator.h b/content/common/gpu/media/vt_video_decode_accelerator.h
index 185d0fb1b77b039553a79feed89f3d5495f1163e..a618405171da612ea3f457eb0268d36853757c77 100644
--- a/content/common/gpu/media/vt_video_decode_accelerator.h
+++ b/content/common/gpu/media/vt_video_decode_accelerator.h
@@ -64,16 +64,39 @@ class VTVideoDecodeAccelerator
     base::ScopedCFTypeRef<CVImageBufferRef> image_buffer;
   };
 
+  enum Action {

[Pawel Osciak, 2014/09/25 01:27:29]

Please document this and the class.

[sandersd (OOO until July 31), 2014/09/25 19:18:53]

Done.

+    ACTION_FLUSH,
+    ACTION_RESET,
+    ACTION_DESTROY
+  };
+
+  struct PendingAction {
+    PendingAction(Action action, int32_t bitstream_id);
+    ~PendingAction();
+
+    Action action;
+    int32_t bitstream_id;
+  };
+
   // Methods for interacting with VideoToolbox. Run on |decoder_thread_|.
   void ConfigureDecoder(
       const std::vector<const uint8_t*>& nalu_data_ptrs,
       const std::vector<size_t>& nalu_data_sizes);
   void DecodeTask(const media::BitstreamBuffer);
+  void FlushTask();
 
   // Methods for interacting with |client_|. Run on |gpu_task_runner_|.
   void OutputTask(DecodedFrame frame);
   void SizeChangedTask(gfx::Size coded_size);
-  void SendPictures();
+
+  // Send decoded frames up to and including |up_to_bitstream_id|, and return
+  // the last sent |bitstream_id|.
+  int32_t SendPictures(int32_t up_to_bitstream_id);
+
+  void ProcessDecodedFrames();

[Pawel Osciak, 2014/09/25 01:27:29]

Please document.

[sandersd (OOO until July 31), 2014/09/25 19:18:53]

Done.

+  void CompleteAction(Action action);
+  void CompleteActions(int32_t bitstream_id);
+  void QueueAction(Action action);
 
   //
   // GPU thread state.
@@ -82,6 +105,14 @@ class VTVideoDecodeAccelerator
   media::VideoDecodeAccelerator::Client* client_;
   gfx::Size texture_size_;
 
+  // Since VideoToolbox has no reset feature (only flush), and the VDA API
+  // allows Decode() and Flush() calls during a reset operation, it's possible
+  // to have multiple pending actions at once. We handle the fully general
+  // case of an arbitrary sequence of pending actions (in reality, there should
+  // probably be at most one reset and one flush at a time).
+  std::queue<PendingAction> pending_actions_;
+  std::queue<int32_t> pending_bitstream_ids_;
+
   // Texture IDs of pictures.
   // TODO(sandersd): A single map of structs holding picture data.
   std::map<int32_t, uint32_t> texture_ids_;
@@ -105,7 +136,7 @@ class VTVideoDecodeAccelerator
   gfx::Size coded_size_;
 
   //
-  // Unprotected shared state (set up and torn down on GPU thread).
+  // Shared state (set up and torn down on GPU thread).
   //
   scoped_refptr<base::SingleThreadTaskRunner> gpu_task_runner_;