VideoToolbox encoder for cast senders.

media/cast/sender/h264_vt_encoder.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_CAST_SENDER_H264_VT_ENCODER_H_
+#define MEDIA_CAST_SENDER_H264_VT_ENCODER_H_
+
+#include <CoreMedia/CoreMedia.h>
+#include <VideoToolbox/VideoToolbox.h>
+#include <string>
+
+#include "base/mac/scoped_cftyperef.h"
+#include "base/threading/thread_checker.h"
+#include "media/cast/sender/video_encoder.h"
+
+namespace media {
+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.
+class H264VideoToolboxEncoder : public VideoEncoder {
+ public:
+  H264VideoToolboxEncoder(scoped_refptr<CastEnvironment> cast_environment,
+                          const VideoSenderConfig& video_config);
+  virtual ~H264VideoToolboxEncoder();
+
+  // After Initialize has been called, returns the compression session's
+  // internal pixel buffer pool. Clients can use it to provide video frames that
+  // will not incur a copy into encoder-accessible memory.
+  CVPixelBufferPoolRef cv_pixel_buffer_pool() const;
+
+  // media::cast::VideoEncoder implementation
+  virtual bool EncodeVideoFrame(
+      const scoped_refptr<media::VideoFrame>& video_frame,
+      const base::TimeTicks& capture_time,
+      const FrameEncodedCallback& frame_encoded_callback) OVERRIDE;
+  virtual void SetBitRate(int new_bit_rate) OVERRIDE;
+  virtual void GenerateKeyFrame() OVERRIDE;
+  virtual void LatestFrameIdToReference(uint32 frame_id) OVERRIDE;
+
+ private:
+  // Initialize the compression session.
+  void Initialize();
+
+  // Configure the compression session.
+  void ConfigureSession();
+
+  // Teardown the encoder.
+  void Teardown();
+
+  // Wrap a VideoFrame in a new CVPixelBuffer
+  base::ScopedCFTypeRef<CVPixelBufferRef> WrapVideoFrame(
+      const scoped_refptr<media::VideoFrame>& frame);
+
+  // Compression session callback function to handle compressed frames.
+  static void CompressionCallback(void* encoder_opaque,
+                                  void* frame_opaque,
+                                  OSStatus status,
+                                  VTEncodeInfoFlags info,
+                                  CMSampleBufferRef sbuf);
+
+  // Copy a H.264 frame stored in a CM sample buffer to an Annex B buffer.
+  // Copies parameter sets for keyframes before the frame data.
+  static void CopySampleBufferToAnnexBBuffer(CMSampleBufferRef sbuf,
+                                             std::string* annexb_buffer,
+                                             bool keyframe);
+
+  // The cast environment (contains worker threads & more).
+  const scoped_refptr<CastEnvironment> cast_environment_;
+
+  // The cast video configuration (contains resolution, bitrate & more).
+  const VideoSenderConfig cast_config_;

[miu, 2014/08/25 19:21:17]

nit: You don't need this member, as it's only used in Initialize() and
ConfigureSession(), both of which are called from the ctor.  So, you could just
pass it as an arg when calling these two methods.

[jfroy, 2014/08/25 20:59:13]

Done.

+
+  // Thread checker to enforce that this object is used on a specific thread.
+  base::ThreadChecker thread_checker_;
+
+  // The compression session.
+  base::ScopedCFTypeRef<VTCompressionSessionRef> compression_session_;
+
+  // Frame identifier counter.
+  uint32 frame_id_;
+
+  // Frame identifier of the last encoded keyframe.
+  uint32 last_keyframe_id_;
+
+  // Force next frame to be a keyframe.
+  bool encode_next_frame_as_keyframe_;
+
+  DISALLOW_COPY_AND_ASSIGN(H264VideoToolboxEncoder);
+};
+
+}  // namespace cast
+}  // namespace media
+
+#endif  // MEDIA_CAST_SENDER_H264_VT_ENCODER_H_