media/capture/webm_muxer.h

// Copyright 2015 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_FILTERS_LIBWEBM_MUXER_H_
#define MEDIA_FILTERS_LIBWEBM_MUXER_H_

#include "base/callback.h"
#include "base/numerics/safe_math.h"
#include "base/strings/string_piece.h"
#include "base/threading/thread_checker.h"
#include "base/time/time.h"
#include "media/base/media_export.h"
#include "media/base/video_codecs.h"
#include "third_party/libwebm/source/mkvmuxer.hpp"

namespace gfx {
class Size;
}  // namespace gfx

namespace media {

class VideoFrame;

// Adapter class to manage a WebM container [1], a simplified version of a
// Matroska container [2], composed of an EBML header, and a single Segment
// including at least a Track Section and a number of SimpleBlocks each
// containing a single encoded video frame. WebM container has no Trailer.
// Clients will push encoded VPx video frames one by one via OnEncodedVideo().
// libwebm will eventually ping the WriteDataCB passed on contructor with the
// wrapped encoded data.
// WebmMuxer is designed for single thread use throughout.
// [1] http://www.webmproject.org/docs/container/
// [2] http://www.matroska.org/technical/specs/index.html
// TODO(mcasas): Add support for Audio muxing.
class MEDIA_EXPORT WebmMuxer : public NON_EXPORTED_BASE(mkvmuxer::IMkvWriter) {
 public:
  // Callback to be called when WebmMuxer is ready to write a chunk of data,
  // either any file header or a SingleBlock.
  using WriteDataCB = base::Callback<void(base::StringPiece)>;

  // |codec| can be VP8 or VP9 and should coincide with whatever is sent in
  // OnEncodedVideo().
  WebmMuxer(VideoCodec codec, const WriteDataCB& write_data_callback);
  ~WebmMuxer() override;

  // Adds a |video_frame| with |encoded_data.data()| to WebM Segment.
  void OnEncodedVideo(const scoped_refptr<VideoFrame>& video_frame,
                      scoped_ptr<std::string> encoded_data,
                      base::TimeTicks timestamp,
                      bool is_key_frame);

 private:
  friend class WebmMuxerTest;

  // Creates and adds a new video track. Called upon receiving the first
  // frame of a given Track, adds |frame_size| and |frame_rate| to the Segment
  // info, although individual frames passed to OnEncodedVideo() can have any
  // frame size.
  void AddVideoTrack(const gfx::Size& frame_size, double frame_rate);

  // IMkvWriter interface.
  mkvmuxer::int32 Write(const void* buf, mkvmuxer::uint32 len) override;
  mkvmuxer::int64 Position() const override;
  mkvmuxer::int32 Position(mkvmuxer::int64 position) override;
  bool Seekable() const override;
  void ElementStartNotify(mkvmuxer::uint64 element_id,
                          mkvmuxer::int64 position) override;

  // Used to DCHECK that we are called on the correct thread.
  base::ThreadChecker thread_checker_;

  // Video Codec configured: VP9 if true, otherwise VP8 is used by default.
  const bool use_vp9_;

  // A caller-side identifier to interact with |segment_|, initialised upon
  // first frame arrival by AddVideoTrack().
  uint64_t track_index_;

  // Origin of times for frame timestamps.
  base::TimeTicks first_frame_timestamp_;

  // Callback to dump written data as being called by libwebm.
  const WriteDataCB write_data_callback_;

  // Rolling counter of the position in bytes of the written goo.
  base::CheckedNumeric<mkvmuxer::int64> position_;

  // The MkvMuxer active element.
  mkvmuxer::Segment segment_;

  DISALLOW_COPY_AND_ASSIGN(WebmMuxer);
};

}  // namespace media

#endif  // MEDIA_FILTERS_LIBWEBM_MUXER_H_