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 "base/mac/scoped_cftyperef.h"
+#include "base/threading/thread_checker.h"
+#include "media/cast/sender/video_encoder.h"
+
+// From CoreMedia, CoreVideo and VideoToolbox
+typedef struct opaqueCMSampleBuffer* CMSampleBufferRef;
+typedef struct __CVPixelBufferPool* CVPixelBufferPoolRef;
+typedef struct OpaqueVTCompressionSession* VTCompressionSessionRef;
+typedef UInt32 VTEncodeInfoFlags;
+
+namespace media {
+namespace cast {
+
+// VideoToolbox implementation of the VideoEncoder interface.
+class H264VideoToolboxEncoder : public VideoEncoder {
+ public:
+  typedef base::ScopedCFTypeRef<CVPixelBufferRef> PixelBufferPtr;
+
+  explicit H264VideoToolboxEncoder(

[miu, 2014/08/08 17:53:09]

Don't need 'explicit' with 2-arg ctor.

[jfroy, 2014/08/11 20:49:13]

Acknowledged.

+      scoped_refptr<CastEnvironment> cast_environment,
+      const VideoSenderConfig& video_config);
+  virtual ~H264VideoToolboxEncoder();
+
+  // After Initialize has been called, this will return the compression
+  // session's internal pixel buffer pool. Clients that create this encoder
+  // explicitly probably have knowledge of CoreVideo and can use this pool to
+  // ensure they send compatible and optimized buffers to the encoder.
+  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:
+  typedef base::ScopedCFTypeRef<CFDictionaryRef> DictionaryPtr;
+  struct FrameContext;
+
+  // Initialize the compression session.
+  void Initialize();
+
+  // Configures the compression session.
+  void ConfigureSession();
+
+  // Teardown the encoder.
+  void Teardown();
+
+  // Wrap a VideoFrame in a new CVPixelBuffer
+  PixelBufferPtr WrapVideoFrame(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);
+
+  // Copies an H264 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).
+  scoped_refptr<CastEnvironment> cast_environment_;

[miu, 2014/08/08 17:53:09]

nit: const scoped_refptr<CastEnvironment> cast_environment_;
     ^^^^

(since this member is never changed after construction)

[jfroy, 2014/08/11 20:49:13]

Acknowledged.

+
+  // The cast video configuration (contains resolution, bitrate & more).
+  const VideoSenderConfig cast_config_;
+
+  // Additional properties to apply on the compression session. See
+  // VTCompressionSessionProperties.h. Will override any properties set by the
+  // this class (i.e. this dictionary is applied last without filtering).
+  DictionaryPtr compression_properties_;
+
+  // 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.
+  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_;
+
+  // Are we actually using a hardware encoder. On some platforms under certain
+  // conditions, VT will fallback to software.
+  bool using_hardware_;

[miu, 2014/08/08 17:53:09]

It doesn't look like this is being used for anything.  It's being set, but did
you mean to expose it externally for some reason?

If you decide to keep it, please add using_hardware_(false) to the ctor's
initializer list.

[jfroy, 2014/08/11 20:50:06]

Acknowledged.

+
+  // 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_