media/cast/sender/video_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_VIDEO_ENCODER_H_
#define MEDIA_CAST_SENDER_VIDEO_ENCODER_H_

#include <memory>

#include "base/callback.h"
#include "base/memory/ref_counted.h"
#include "base/time/time.h"
#include "media/base/video_frame.h"
#include "media/cast/cast_config.h"
#include "media/cast/cast_environment.h"
#include "media/cast/cast_sender.h"
#include "media/cast/sender/sender_encoded_frame.h"
#include "media/cast/sender/video_frame_factory.h"

namespace media {
namespace cast {

// All these functions are called from the main cast thread.
class VideoEncoder {
 public:
  // Callback used to deliver an encoded frame on the Cast MAIN thread.
  using FrameEncodedCallback =
      base::OnceCallback<void(std::unique_ptr<SenderEncodedFrame>)>;

  // Creates a VideoEncoder instance from the given |video_config| and based on
  // the current platform's hardware/library support; or null if no
  // implementation will suffice.  The instance will run |status_change_cb| at
  // some point in the future to indicate initialization success/failure.
  //
  // All VideoEncoder instances returned by this function support encoding
  // sequences of differently-size VideoFrames.
  static std::unique_ptr<VideoEncoder> Create(
      const scoped_refptr<CastEnvironment>& cast_environment,
      const FrameSenderConfig& video_config,
      StatusChangeCallback status_change_cb,
      const CreateVideoEncodeAcceleratorCallback& create_vea_cb);

  virtual ~VideoEncoder() {}

  // If true is returned, the Encoder has accepted the request and will process
  // it asynchronously, running |frame_encoded_callback| on the MAIN
  // CastEnvironment thread with the result.  If false is returned, nothing
  // happens and the callback will not be run.
  virtual bool EncodeVideoFrame(
      scoped_refptr<media::VideoFrame> video_frame,
      base::TimeTicks reference_time,
      FrameEncodedCallback frame_encoded_callback) = 0;

  // Inform the encoder about the new target bit rate.
  virtual void SetBitRate(int new_bit_rate) = 0;

  // Inform the encoder to encode the next frame as a key frame.
  virtual void GenerateKeyFrame() = 0;

  // Creates a |VideoFrameFactory| object to vend |VideoFrame| object with
  // encoder affinity (defined as offering some sort of performance benefit).
  // This is an optional capability and by default returns null.
  virtual std::unique_ptr<VideoFrameFactory> CreateVideoFrameFactory();

  // Instructs the encoder to finish and emit all frames that have been
  // submitted for encoding. An encoder may hold a certain number of frames for
  // analysis. Under certain network conditions, particularly when there is
  // network congestion, it is necessary to flush out of the encoder all
  // submitted frames so that eventually new frames may be encoded. Like
  // EncodeVideoFrame(), the encoder will process this request asynchronously.
  virtual void EmitFrames();
};

}  // namespace cast
}  // namespace media

#endif  // MEDIA_CAST_SENDER_VIDEO_ENCODER_H_