[cast] Handle frame size changes directly in the VideoToolbox encoder (v2).

media/cast/sender/h264_vt_encoder.h

Index: media/cast/sender/h264_vt_encoder.h
diff --git a/media/cast/sender/h264_vt_encoder.h b/media/cast/sender/h264_vt_encoder.h
index ece6ab38b1a6f362cdd27207a1b48ad9c284668d..756571c0c10bb804ae46e26556bfeb2c248ea4f0 100644
--- a/media/cast/sender/h264_vt_encoder.h
+++ b/media/cast/sender/h264_vt_encoder.h
@@ -16,7 +16,8 @@ namespace cast {
 
 // VideoToolbox implementation of the media::cast::VideoEncoder interface.
 // VideoToolbox makes no guarantees that it is thread safe, so this object is
-// pinned to the thread on which it is constructed.
+// pinned to the thread on which it is constructed. Supports changing frame
+// sizes directly.
 class H264VideoToolboxEncoder : public VideoEncoder {
   typedef CoreMediaGlue::CMSampleBufferRef CMSampleBufferRef;
   typedef VideoToolboxGlue::VTCompressionSessionRef VTCompressionSessionRef;
@@ -30,8 +31,6 @@ class H264VideoToolboxEncoder : public VideoEncoder {
   H264VideoToolboxEncoder(
       const scoped_refptr<CastEnvironment>& cast_environment,
       const VideoSenderConfig& video_config,
-      const gfx::Size& frame_size,
-      uint32 first_frame_id,
       const StatusChangeCallback& status_change_cb);
   ~H264VideoToolboxEncoder() override;
 
@@ -47,14 +46,25 @@ class H264VideoToolboxEncoder : public VideoEncoder {
   void EmitFrames() override;
 
  private:
-  // Initialize the compression session.
-  bool Initialize(const VideoSenderConfig& video_config);
+  // VideoFrameFactory tied to the VideoToolbox encoder.
+  class VideoFrameFactoryImpl;
 
-  // Configure the compression session.
-  void ConfigureSession(const VideoSenderConfig& video_config);
+  // Reset the encoder's compression session by destroying the existing one
+  // using DestroyCompressionSession() and creating a new one. The new session
+  // is configured using ConfigureCompressionSession().
+  void ResetCompressionSession();
 
-  // Teardown the encoder.
-  void Teardown();
+  // Configure the current compression session using current encoder settings.
+  void ConfigureCompressionSession();
+
+  // Destroy the current compression session if any. Blocks until all pending
+  // frames have been flushed out (similar to EmitFrames without doing any
+  // encoding work).
+  void DestroyCompressionSession();
+
+  // Update the encoder's target frame size by resetting the compression
+  // session. This will also update the video frame factory.
+  void UpdateFrameSize(const gfx::Size& size_needed);
 
   // Set a compression session property.
   bool SetSessionProperty(CFStringRef key, int32_t value);
@@ -74,8 +84,14 @@ class H264VideoToolboxEncoder : public VideoEncoder {
   // VideoToolboxGlue provides access to VideoToolbox at runtime.
   const VideoToolboxGlue* const videotoolbox_glue_;
 
-  // The size of the visible region of the video frames to be encoded.
-  const gfx::Size frame_size_;
+  // VideoSenderConfig copy so we can create compression sessions on demand.
+  // This is needed to recover from backgrounding and other events that can
+  // invalidate compression sessions.
+  const VideoSenderConfig video_config_;
+
+  // Frame size of the current compression session. Can be changed by submitting
+  // a frame of a different size, which will cause a compression session reset.
+  gfx::Size frame_size_;
 
   // Callback used to report initialization status and runtime errors.
   const StatusChangeCallback status_change_cb_;
@@ -86,41 +102,19 @@ class H264VideoToolboxEncoder : public VideoEncoder {
   // The compression session.
   base::ScopedCFTypeRef<VTCompressionSessionRef> compression_session_;
 
-  // Frame identifier counter.
-  uint32 next_frame_id_;
+  // Video frame factory tied to the encoder.
+  scoped_refptr<VideoFrameFactoryImpl> video_frame_factory_;
+
+  // The ID of the last frame that was emitted.
+  uint32 last_frame_id_;
 
   // Force next frame to be a keyframe.
   bool encode_next_frame_as_keyframe_;
 
-  DISALLOW_COPY_AND_ASSIGN(H264VideoToolboxEncoder);
-};
+  // NOTE: Weak pointers must be invalidated before all other member variables.
+  base::WeakPtrFactory<H264VideoToolboxEncoder> weak_factory_;
 
-// An implementation of SizeAdaptableVideoEncoderBase to proxy for
-// H264VideoToolboxEncoder instances.
-class SizeAdaptableH264VideoToolboxVideoEncoder
- : public SizeAdaptableVideoEncoderBase {
- public:
-  SizeAdaptableH264VideoToolboxVideoEncoder(
-      const scoped_refptr<CastEnvironment>& cast_environment,
-      const VideoSenderConfig& video_config,
-      const StatusChangeCallback& status_change_cb);
-
-  ~SizeAdaptableH264VideoToolboxVideoEncoder() override;
-
-  scoped_ptr<VideoFrameFactory> CreateVideoFrameFactory() override;
-
- protected:
-  scoped_ptr<VideoEncoder> CreateEncoder() override;
-  void OnEncoderReplaced(VideoEncoder* replacement_encoder) override;
-  void DestroyEncoder() override;
-
- private:
-  struct FactoryHolder;
-  class VideoFrameFactoryProxy;
-
-  const scoped_refptr<FactoryHolder> holder_;
-
-  DISALLOW_COPY_AND_ASSIGN(SizeAdaptableH264VideoToolboxVideoEncoder);
+  DISALLOW_COPY_AND_ASSIGN(H264VideoToolboxEncoder);
 };
 
 }  // namespace cast