Implement actually decoding frames 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 08dd8ab8454ca08a1b6fbaa48133643087aa874e..8190c3270648ed7dacaf671cdd7690270d952a1e 100644
--- a/content/common/gpu/media/vt_video_decode_accelerator.h
+++ b/content/common/gpu/media/vt_video_decode_accelerator.h
@@ -5,11 +5,16 @@
 #ifndef CONTENT_COMMON_GPU_MEDIA_VT_VIDEO_DECODE_ACCELERATOR_H_
 #define CONTENT_COMMON_GPU_MEDIA_VT_VIDEO_DECODE_ACCELERATOR_H_
 
+#include <map>
+#include <queue>
+
 #include "base/basictypes.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
+#include "base/synchronization/lock.h"
 #include "base/threading/thread.h"
 #include "content/common/gpu/media/vt.h"
 #include "media/filters/h264_parser.h"
@@ -53,6 +58,14 @@ class VTVideoDecodeAccelerator
       CVImageBufferRef image_buffer);
 
  private:
+  struct DecodedFrame {
+    DecodedFrame(uint32_t bitstream_id, CVImageBufferRef image_buffer);
+    ~DecodedFrame();
+
+    int32_t bitstream_id;
+    base::ScopedCFTypeRef<CVImageBufferRef> image_buffer;
+  };
+
   // Configure a VideoToolbox decompression session from parameter set NALUs.

[scherkus (not reviewing), 2014/07/17 02:08:26]

general comment on comments: comments that are an english sentence equivalent of
their method names aren't helpful.

more helpful comments would include (as an example), grouping functions together
by the thread they run on

// Methods interacting with VideoToolbox. Run on |decoder_thread_|.
void ConfigureDecoder(...);
void DecodeTask(...);

// Methods interacting with |weak_client_factory_|. Run on |gpu_task_runner_|.
void OutputTask(...);
void SendPictures();

[sandersd (OOO until July 31), 2014/07/17 20:31:46]

Done.

   void ConfigureDecoder(
       const std::vector<const uint8_t*>& nalu_data_ptrs,
@@ -61,22 +74,58 @@ class VTVideoDecodeAccelerator
   // Decode a frame of bitstream.
   void DecodeTask(const media::BitstreamBuffer);
 
+  // Handle a decoded frame.
+  void OutputTask(
+      int32_t bitstream_id,
+      base::ScopedCFTypeRef<CVImageBufferRef> image_buffer);
+
+  // Send decoded frames if possible.
+  void SendPictures();
+
+  //
+  // GPU thread state.
+  //
   CGLContextObj cgl_context_;
-  media::VideoDecodeAccelerator::Client* client_;
-  base::Thread decoder_thread_;
+  // Texture IDs of pictures.
+  std::map<int32_t, int32_t> texture_ids_;
+  // Pictures ready to be rendered to.
+  std::queue<int32_t> picture_ids_;
+  // Decoded frames ready to render.
+  std::queue<DecodedFrame> decoded_frames_;
+  // Image buffers retained while they are bound to textures.
+  std::map<int32_t, base::ScopedCFTypeRef<CVImageBufferRef>> picture_bindings_;
 
-  // Decoder configuration (used only on decoder thread).
+  //
+  // Decoder thread state.
+  //
   VTDecompressionOutputCallbackRecord callback_;
   base::ScopedCFTypeRef<CMFormatDescriptionRef> format_;
   base::ScopedCFTypeRef<VTDecompressionSessionRef> session_;
   media::H264Parser parser_;
   gfx::Size coded_size_;
 
-  // Member variables should appear before the WeakPtrFactory, to ensure
-  // that any WeakPtrs to Controller are invalidated before its members
-  // variable's destructors are executed, rendering them invalid.
+  //
+  // Lock-protected shared state.
+  //
+  base::Lock lock_;
+  // Number of frames pending inside VideoToolbox.
+  size_t frames_pending_decode_;
+
+  //
+  // Unprotected shared state (set up and torn down on GPU thread).
+  //
+  scoped_refptr<base::SingleThreadTaskRunner> gpu_task_runner_;
+  scoped_ptr<base::WeakPtrFactory<media::VideoDecodeAccelerator::Client>>
+      weak_client_factory_;
+
+  // Declared second-to-last to prevent any GPU thread tasks from executing once
+  // state starts being destroyed.
   base::WeakPtrFactory<VTVideoDecodeAccelerator> weak_this_factory_;
 
+  // Declared last to ensure that all decoder thread tasks complete before any
+  // state starts being destroyed.
+  base::Thread decoder_thread_;
+
   DISALLOW_COPY_AND_ASSIGN(VTVideoDecodeAccelerator);
 };