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.

[Robert Sesek, 2014/08/12 00:06:12]

Hoist the comment about thread safety up to this class-level comment.

[jfroy, 2014/08/12 01:04:15]

Acknowledged.

+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_;
+
+  // VideoToolbox makes no guarantees that it is thread safe, so use a thread
+  // checker to enforce that this object is pinned on a specific thread. The
+  // binding occurs in Initialize(), not the ctor.

[Robert Sesek, 2014/08/12 00:06:12]

This comment is misleading, since Initialize is only called from the ctor.

[jfroy, 2014/08/12 01:04:15]

Acknowledged.

+  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_