libvpx: Pull from upstream

source/libvpx/third_party/libwebm/mkvmuxer.hpp

+// Copyright (c) 2012 The WebM project authors. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the LICENSE file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS.  All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+
+#ifndef MKVMUXER_HPP
+#define MKVMUXER_HPP
+
+#include "mkvmuxertypes.hpp"
+
+// For a description of the WebM elements see
+// http://www.webmproject.org/code/specs/container/.
+
+namespace mkvparser {
+  class IMkvReader;
+}  // end namespace
+
+namespace mkvmuxer {
+
+class MkvWriter;
+class Segment;
+
+///////////////////////////////////////////////////////////////
+// Interface used by the mkvmuxer to write out the Mkv data.
+class IMkvWriter {
+ public:
+  // Writes out |len| bytes of |buf|. Returns 0 on success.
+  virtual int32 Write(const void* buf, uint32 len) = 0;
+
+  // Returns the offset of the output position from the beginning of the
+  // output.
+  virtual int64 Position() const = 0;
+
+  // Set the current File position. Returns 0 on success.
+  virtual int32 Position(int64 position) = 0;
+
+  // Returns true if the writer is seekable.
+  virtual bool Seekable() const = 0;
+
+  // Element start notification. Called whenever an element identifier is about
+  // to be written to the stream. |element_id| is the element identifier, and
+  // |position| is the location in the WebM stream where the first octet of the
+  // element identifier will be written.
+  // Note: the |MkvId| enumeration in webmids.hpp defines element values.
+  virtual void ElementStartNotify(uint64 element_id, int64 position) = 0;
+
+ protected:
+  IMkvWriter();
+  virtual ~IMkvWriter();
+
+ private:
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(IMkvWriter);
+};
+
+// Writes out the EBML header for a WebM file. This function must be called
+// before any other libwebm writing functions are called.
+bool WriteEbmlHeader(IMkvWriter* writer);
+
+// Copies in Chunk from source to destination between the given byte positions
+bool ChunkedCopy(mkvparser::IMkvReader* source, IMkvWriter* dst,
+                 int64 start, int64 size);
+
+///////////////////////////////////////////////////////////////
+// Class to hold data the will be written to a block.
+class Frame {
+ public:
+  Frame();
+  ~Frame();
+
+  // Copies |frame| data into |frame_|. Returns true on success.
+  bool Init(const uint8* frame, uint64 length);
+
+  // Copies |additional| data into |additional_|. Returns true on success.
+  bool AddAdditionalData(const uint8* additional, uint64 length,
+                         uint64 add_id);
+
+  uint64 add_id() const { return add_id_; }
+  const uint8* additional() const { return additional_; }
+  uint64 additional_length() const { return additional_length_; }
+  void set_duration(uint64 duration) { duration_ = duration; }
+  uint64 duration() const { return duration_; }
+  const uint8* frame() const { return frame_; }
+  void set_is_key(bool key) { is_key_ = key; }
+  bool is_key() const { return is_key_; }
+  uint64 length() const { return length_; }
+  void set_track_number(uint64 track_number) { track_number_ = track_number; }
+  uint64 track_number() const { return track_number_; }
+  void set_timestamp(uint64 timestamp) { timestamp_ = timestamp; }
+  uint64 timestamp() const { return timestamp_; }
+  void set_discard_padding(uint64 discard_padding) {
+    discard_padding_ = discard_padding;
+  }
+  uint64 discard_padding() const { return discard_padding_; }
+
+ private:
+  // Id of the Additional data.
+  uint64 add_id_;
+
+  // Pointer to additional data. Owned by this class.
+  uint8* additional_;
+
+  // Length of the additional data.
+  uint64 additional_length_;
+
+  // Duration of the frame in nanoseconds.
+  uint64 duration_;
+
+  // Pointer to the data. Owned by this class.
+  uint8* frame_;
+
+  // Flag telling if the data should set the key flag of a block.
+  bool is_key_;
+
+  // Length of the data.
+  uint64 length_;
+
+  // Mkv track number the data is associated with.
+  uint64 track_number_;
+
+  // Timestamp of the data in nanoseconds.
+  uint64 timestamp_;
+
+  // Discard padding for the frame.
+  int64 discard_padding_;
+};
+
+///////////////////////////////////////////////////////////////
+// Class to hold one cue point in a Cues element.
+class CuePoint {
+ public:
+  CuePoint();
+  ~CuePoint();
+
+  // Returns the size in bytes for the entire CuePoint element.
+  uint64 Size() const;
+
+  // Output the CuePoint element to the writer. Returns true on success.
+  bool Write(IMkvWriter* writer) const;
+
+  void set_time(uint64 time) { time_ = time; }
+  uint64 time() const { return time_; }
+  void set_track(uint64 track) { track_ = track; }
+  uint64 track() const { return track_; }
+  void set_cluster_pos(uint64 cluster_pos) { cluster_pos_ = cluster_pos; }
+  uint64 cluster_pos() const { return cluster_pos_; }
+  void set_block_number(uint64 block_number) { block_number_ = block_number; }
+  uint64 block_number() const { return block_number_; }
+  void set_output_block_number(bool output_block_number) {
+    output_block_number_ = output_block_number;
+  }
+  bool output_block_number() const { return output_block_number_; }
+
+ private:
+  // Returns the size in bytes for the payload of the CuePoint element.
+  uint64 PayloadSize() const;
+
+  // Absolute timecode according to the segment time base.
+  uint64 time_;
+
+  // The Track element associated with the CuePoint.
+  uint64 track_;
+
+  // The position of the Cluster containing the Block.
+  uint64 cluster_pos_;
+
+  // Number of the Block within the Cluster, starting from 1.
+  uint64 block_number_;
+
+  // If true the muxer will write out the block number for the cue if the
+  // block number is different than the default of 1. Default is set to true.
+  bool output_block_number_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(CuePoint);
+};
+
+///////////////////////////////////////////////////////////////
+// Cues element.
+class Cues {
+ public:
+  Cues();
+  ~Cues();
+
+  // Adds a cue point to the Cues element. Returns true on success.
+  bool AddCue(CuePoint* cue);
+
+  // Returns the cue point by index. Returns NULL if there is no cue point
+  // match.
+  CuePoint* GetCueByIndex(int32 index) const;
+
+  // Returns the total size of the Cues element
+  uint64 Size();
+
+  // Output the Cues element to the writer. Returns true on success.
+  bool Write(IMkvWriter* writer) const;
+
+  int32 cue_entries_size() const { return cue_entries_size_; }
+  void set_output_block_number(bool output_block_number) {
+    output_block_number_ = output_block_number;
+  }
+  bool output_block_number() const { return output_block_number_; }
+
+ private:
+  // Number of allocated elements in |cue_entries_|.
+  int32 cue_entries_capacity_;
+
+  // Number of CuePoints in |cue_entries_|.
+  int32 cue_entries_size_;
+
+  // CuePoint list.
+  CuePoint** cue_entries_;
+
+  // If true the muxer will write out the block number for the cue if the
+  // block number is different than the default of 1. Default is set to true.
+  bool output_block_number_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(Cues);
+};
+
+///////////////////////////////////////////////////////////////
+// ContentEncAESSettings element
+class ContentEncAESSettings {
+ public:
+  enum {
+    kCTR = 1
+  };
+
+  ContentEncAESSettings();
+  ~ContentEncAESSettings() {}
+
+  // Returns the size in bytes for the ContentEncAESSettings element.
+  uint64 Size() const;
+
+  // Writes out the ContentEncAESSettings element to |writer|. Returns true on
+  // success.
+  bool Write(IMkvWriter* writer) const;
+
+  uint64 cipher_mode() const { return cipher_mode_; }
+
+ private:
+  // Returns the size in bytes for the payload of the ContentEncAESSettings
+  // element.
+  uint64 PayloadSize() const;
+
+  // Sub elements
+  uint64 cipher_mode_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(ContentEncAESSettings);
+};
+
+///////////////////////////////////////////////////////////////
+// ContentEncoding element
+// Elements used to describe if the track data has been encrypted or
+// compressed with zlib or header stripping.
+// Currently only whole frames can be encrypted with AES. This dictates that
+// ContentEncodingOrder will be 0, ContentEncodingScope will be 1,
+// ContentEncodingType will be 1, and ContentEncAlgo will be 5.
+class ContentEncoding {
+ public:
+  ContentEncoding();
+  ~ContentEncoding();
+
+  // Sets the content encryption id. Copies |length| bytes from |id| to
+  // |enc_key_id_|. Returns true on success.
+  bool SetEncryptionID(const uint8* id, uint64 length);
+
+  // Returns the size in bytes for the ContentEncoding element.
+  uint64 Size() const;
+
+  // Writes out the ContentEncoding element to |writer|. Returns true on
+  // success.
+  bool Write(IMkvWriter* writer) const;
+
+  uint64 enc_algo() const { return enc_algo_; }
+  uint64 encoding_order() const { return encoding_order_; }
+  uint64 encoding_scope() const { return encoding_scope_; }
+  uint64 encoding_type() const { return encoding_type_; }
+  ContentEncAESSettings* enc_aes_settings() { return &enc_aes_settings_; }
+
+ private:
+  // Returns the size in bytes for the encoding elements.
+  uint64 EncodingSize(uint64 compresion_size, uint64 encryption_size) const;
+
+  // Returns the size in bytes for the encryption elements.
+  uint64 EncryptionSize() const;
+
+  // Track element names
+  uint64 enc_algo_;
+  uint8* enc_key_id_;
+  uint64 encoding_order_;
+  uint64 encoding_scope_;
+  uint64 encoding_type_;
+
+  // ContentEncAESSettings element.
+  ContentEncAESSettings enc_aes_settings_;
+
+  // Size of the ContentEncKeyID data in bytes.
+  uint64 enc_key_id_length_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(ContentEncoding);
+};
+
+///////////////////////////////////////////////////////////////
+// Track element.
+class Track {
+ public:
+  // The |seed| parameter is used to synthesize a UID for the track.
+  explicit Track(unsigned int* seed);
+  virtual ~Track();
+
+  // Adds a ContentEncoding element to the Track. Returns true on success.
+  virtual bool AddContentEncoding();
+
+  // Returns the ContentEncoding by index. Returns NULL if there is no
+  // ContentEncoding match.
+  ContentEncoding* GetContentEncodingByIndex(uint32 index) const;
+
+  // Returns the size in bytes for the payload of the Track element.
+  virtual uint64 PayloadSize() const;
+
+  // Returns the size in bytes of the Track element.
+  virtual uint64 Size() const;
+
+  // Output the Track element to the writer. Returns true on success.
+  virtual bool Write(IMkvWriter* writer) const;
+
+  // Sets the CodecPrivate element of the Track element. Copies |length|
+  // bytes from |codec_private| to |codec_private_|. Returns true on success.
+  bool SetCodecPrivate(const uint8* codec_private, uint64 length);
+
+  void set_codec_id(const char* codec_id);
+  const char* codec_id() const { return codec_id_; }
+  const uint8* codec_private() const { return codec_private_; }
+  void set_language(const char* language);
+  const char* language() const { return language_; }
+  void set_max_block_additional_id(uint64 max_block_additional_id) {
+    max_block_additional_id_ = max_block_additional_id;
+  }
+  uint64 max_block_additional_id() const { return max_block_additional_id_; }
+  void set_name(const char* name);
+  const char* name() const { return name_; }
+  void set_number(uint64 number) { number_ = number; }
+  uint64 number() const { return number_; }
+  void set_type(uint64 type) { type_ = type; }
+  uint64 type() const { return type_; }
+  void set_uid(uint64 uid) { uid_ = uid; }
+  uint64 uid() const { return uid_; }
+  void set_codec_delay(uint64 codec_delay) { codec_delay_ = codec_delay; }
+  uint64 codec_delay() const { return codec_delay_; }
+  void set_seek_pre_roll(uint64 seek_pre_roll) {
+    seek_pre_roll_ = seek_pre_roll;
+  }
+  uint64 seek_pre_roll() const { return seek_pre_roll_; }
+
+  uint64 codec_private_length() const { return codec_private_length_; }
+  uint32 content_encoding_entries_size() const {
+    return content_encoding_entries_size_;
+  }
+
+ private:
+  // Track element names
+  char* codec_id_;
+  uint8* codec_private_;
+  char* language_;
+  uint64 max_block_additional_id_;
+  char* name_;
+  uint64 number_;
+  uint64 type_;
+  uint64 uid_;
+  uint64 codec_delay_;
+  uint64 seek_pre_roll_;
+
+  // Size of the CodecPrivate data in bytes.
+  uint64 codec_private_length_;
+
+  // ContentEncoding element list.
+  ContentEncoding** content_encoding_entries_;
+
+  // Number of ContentEncoding elements added.
+  uint32 content_encoding_entries_size_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(Track);
+};
+
+///////////////////////////////////////////////////////////////
+// Track that has video specific elements.
+class VideoTrack : public Track {
+ public:
+  // Supported modes for stereo 3D.
+  enum StereoMode {
+    kMono = 0,
+    kSideBySideLeftIsFirst  = 1,
+    kTopBottomRightIsFirst  = 2,
+    kTopBottomLeftIsFirst   = 3,
+    kSideBySideRightIsFirst = 11
+  };
+
+  enum AlphaMode {
+    kNoAlpha = 0,
+    kAlpha  = 1
+  };
+
+  // The |seed| parameter is used to synthesize a UID for the track.
+  explicit VideoTrack(unsigned int* seed);
+  virtual ~VideoTrack();
+
+  // Returns the size in bytes for the payload of the Track element plus the
+  // video specific elements.
+  virtual uint64 PayloadSize() const;
+
+  // Output the VideoTrack element to the writer. Returns true on success.
+  virtual bool Write(IMkvWriter* writer) const;
+
+  // Sets the video's stereo mode. Returns true on success.
+  bool SetStereoMode(uint64 stereo_mode);
+
+  // Sets the video's alpha mode. Returns true on success.
+  bool SetAlphaMode(uint64 alpha_mode);
+
+  void set_display_height(uint64 height) { display_height_ = height; }
+  uint64 display_height() const { return display_height_; }
+  void set_display_width(uint64 width) { display_width_ = width; }
+  uint64 display_width() const { return display_width_; }
+  void set_frame_rate(double frame_rate) { frame_rate_ = frame_rate; }
+  double frame_rate() const { return frame_rate_; }
+  void set_height(uint64 height) { height_ = height; }
+  uint64 height() const { return height_; }
+  uint64 stereo_mode() { return stereo_mode_; }
+  uint64 alpha_mode() { return alpha_mode_; }
+  void set_width(uint64 width) { width_ = width; }
+  uint64 width() const { return width_; }
+
+ private:
+  // Returns the size in bytes of the Video element.
+  uint64 VideoPayloadSize() const;
+
+  // Video track element names.
+  uint64 display_height_;
+  uint64 display_width_;
+  double frame_rate_;
+  uint64 height_;
+  uint64 stereo_mode_;
+  uint64 alpha_mode_;
+  uint64 width_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(VideoTrack);
+};
+
+///////////////////////////////////////////////////////////////
+// Track that has audio specific elements.
+class AudioTrack : public Track {
+ public:
+  // The |seed| parameter is used to synthesize a UID for the track.
+  explicit AudioTrack(unsigned int* seed);
+  virtual ~AudioTrack();
+
+  // Returns the size in bytes for the payload of the Track element plus the
+  // audio specific elements.
+  virtual uint64 PayloadSize() const;
+
+  // Output the AudioTrack element to the writer. Returns true on success.
+  virtual bool Write(IMkvWriter* writer) const;
+
+  void set_bit_depth(uint64 bit_depth) { bit_depth_ = bit_depth; }
+  uint64 bit_depth() const { return bit_depth_; }
+  void set_channels(uint64 channels) { channels_ = channels; }
+  uint64 channels() const { return channels_; }
+  void set_sample_rate(double sample_rate) { sample_rate_ = sample_rate; }
+  double sample_rate() const { return sample_rate_; }
+
+ private:
+  // Audio track element names.
+  uint64 bit_depth_;
+  uint64 channels_;
+  double sample_rate_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(AudioTrack);
+};
+
+///////////////////////////////////////////////////////////////
+// Tracks element
+class Tracks {
+ public:
+  // Audio and video type defined by the Matroska specs.
+  enum {
+    kVideo = 0x1,
+    kAudio = 0x2
+  };
+  // Opus, Vorbis, VP8, and VP9 codec ids defined by the Matroska specs.
+  static const char kOpusCodecId[];
+  static const char kVorbisCodecId[];
+  static const char kVp8CodecId[];
+  static const char kVp9CodecId[];
+
+  Tracks();
+  ~Tracks();
+
+  // Adds a Track element to the Tracks object. |track| will be owned and
+  // deleted by the Tracks object. Returns true on success. |number| is the
+  // number to use for the track. |number| must be >= 0. If |number| == 0
+  // then the muxer will decide on the track number.
+  bool AddTrack(Track* track, int32 number);
+
+  // Returns the track by index. Returns NULL if there is no track match.
+  const Track* GetTrackByIndex(uint32 idx) const;
+
+  // Search the Tracks and return the track that matches |tn|. Returns NULL
+  // if there is no track match.
+  Track* GetTrackByNumber(uint64 track_number) const;
+
+  // Returns true if the track number is an audio track.
+  bool TrackIsAudio(uint64 track_number) const;
+
+  // Returns true if the track number is a video track.
+  bool TrackIsVideo(uint64 track_number) const;
+
+  // Output the Tracks element to the writer. Returns true on success.
+  bool Write(IMkvWriter* writer) const;
+
+  uint32 track_entries_size() const { return track_entries_size_; }
+
+ private:
+  // Track element list.
+  Track** track_entries_;
+
+  // Number of Track elements added.
+  uint32 track_entries_size_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(Tracks);
+};
+
+///////////////////////////////////////////////////////////////
+// Chapter element
+//
+class Chapter {
+ public:
+  // Set the identifier for this chapter.  (This corresponds to the
+  // Cue Identifier line in WebVTT.)
+  // TODO(matthewjheaney): the actual serialization of this item in
+  // MKV is pending.
+  bool set_id(const char* id);
+
+  // Converts the nanosecond start and stop times of this chapter to
+  // their corresponding timecode values, and stores them that way.
+  void set_time(const Segment& segment,
+                uint64 start_time_ns,
+                uint64 end_time_ns);
+
+  // Sets the uid for this chapter. Primarily used to enable
+  // deterministic output from the muxer.
+  void set_uid(const uint64 uid) { uid_ = uid; }
+
+  // Add a title string to this chapter, per the semantics described
+  // here:
+  //  http://www.matroska.org/technical/specs/index.html
+  //
+  // The title ("chapter string") is a UTF-8 string.
+  //
+  // The language has ISO 639-2 representation, described here:
+  //  http://www.loc.gov/standards/iso639-2/englangn.html
+  //  http://www.loc.gov/standards/iso639-2/php/English_list.php
+  // If you specify NULL as the language value, this implies
+  // English ("eng").
+  //
+  // The country value corresponds to the codes listed here:
+  //  http://www.iana.org/domains/root/db/
+  //
+  // The function returns false if the string could not be allocated.
+  bool add_string(const char* title,
+                  const char* language,
+                  const char* country);
+
+ private:
+  friend class Chapters;
+
+  // For storage of chapter titles that differ by language.
+  class Display {
+   public:
+    // Establish representation invariant for new Display object.
+    void Init();
+
+    // Reclaim resources, in anticipation of destruction.
+    void Clear();
+
+    // Copies the title to the |title_| member.  Returns false on
+    // error.
+    bool set_title(const char* title);
+
+    // Copies the language to the |language_| member.  Returns false
+    // on error.
+    bool set_language(const char* language);
+
+    // Copies the country to the |country_| member.  Returns false on
+    // error.
+    bool set_country(const char* country);
+
+    // If |writer| is non-NULL, serialize the Display sub-element of
+    // the Atom into the stream.  Returns the Display element size on
+    // success, 0 if error.
+    uint64 WriteDisplay(IMkvWriter* writer) const;
+
+   private:
+    char* title_;
+    char* language_;
+    char* country_;
+  };
+
+  Chapter();
+  ~Chapter();
+
+  // Establish the representation invariant for a newly-created
+  // Chapter object.  The |seed| parameter is used to create the UID
+  // for this chapter atom.
+  void Init(unsigned int* seed);
+
+  // Copies this Chapter object to a different one.  This is used when
+  // expanding a plain array of Chapter objects (see Chapters).
+  void ShallowCopy(Chapter* dst) const;
+
+  // Reclaim resources used by this Chapter object, pending its
+  // destruction.
+  void Clear();
+
+  // If there is no storage remaining on the |displays_| array for a
+  // new display object, creates a new, longer array and copies the
+  // existing Display objects to the new array.  Returns false if the
+  // array cannot be expanded.
+  bool ExpandDisplaysArray();
+
+  // If |writer| is non-NULL, serialize the Atom sub-element into the
+  // stream.  Returns the total size of the element on success, 0 if
+  // error.
+  uint64 WriteAtom(IMkvWriter* writer) const;
+
+  // The string identifier for this chapter (corresponds to WebVTT cue
+  // identifier).
+  char* id_;
+
+  // Start timecode of the chapter.
+  uint64 start_timecode_;
+
+  // Stop timecode of the chapter.
+  uint64 end_timecode_;
+
+  // The binary identifier for this chapter.
+  uint64 uid_;
+
+  // The Atom element can contain multiple Display sub-elements, as
+  // the same logical title can be rendered in different languages.
+  Display* displays_;
+
+  // The physical length (total size) of the |displays_| array.
+  int displays_size_;
+
+  // The logical length (number of active elements) on the |displays_|
+  // array.
+  int displays_count_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(Chapter);
+};
+
+///////////////////////////////////////////////////////////////
+// Chapters element
+//
+class Chapters {
+ public:
+  Chapters();
+  ~Chapters();
+
+  Chapter* AddChapter(unsigned int* seed);
+
+  // Returns the number of chapters that have been added.
+  int Count() const;
+
+  // Output the Chapters element to the writer. Returns true on success.
+  bool Write(IMkvWriter* writer) const;
+
+ private:
+  // Expands the chapters_ array if there is not enough space to contain
+  // another chapter object.  Returns true on success.
+  bool ExpandChaptersArray();
+
+  // If |writer| is non-NULL, serialize the Edition sub-element of the
+  // Chapters element into the stream.  Returns the Edition element
+  // size on success, 0 if error.
+  uint64 WriteEdition(IMkvWriter* writer) const;
+
+  // Total length of the chapters_ array.
+  int chapters_size_;
+
+  // Number of active chapters on the chapters_ array.
+  int chapters_count_;
+
+  // Array for storage of chapter objects.
+  Chapter* chapters_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(Chapters);
+};
+
+///////////////////////////////////////////////////////////////
+// Cluster element
+//
+// Notes:
+//  |Init| must be called before any other method in this class.
+class Cluster {
+ public:
+  Cluster(uint64 timecode, int64 cues_pos);
+  ~Cluster();
+
+  // |timecode| is the absolute timecode of the cluster. |cues_pos| is the
+  // position for the cluster within the segment that should be written in
+  // the cues element.
+  bool Init(IMkvWriter* ptr_writer);
+
+  // Adds a frame to be output in the file. The frame is written out through
+  // |writer_| if successful. Returns true on success.
+  // Inputs:
+  //   frame: Pointer to the data
+  //   length: Length of the data
+  //   track_number: Track to add the data to. Value returned by Add track
+  //                 functions.  The range of allowed values is [1, 126].
+  //   timecode:     Absolute (not relative to cluster) timestamp of the
+  //                 frame, expressed in timecode units.
+  //   is_key:       Flag telling whether or not this frame is a key frame.
+  bool AddFrame(const uint8* frame,
+                uint64 length,
+                uint64 track_number,
+                uint64 timecode,  // timecode units (absolute)
+                bool is_key);
+
+  // Adds a frame to be output in the file. The frame is written out through
+  // |writer_| if successful. Returns true on success.
+  // Inputs:
+  //   frame: Pointer to the data
+  //   length: Length of the data
+  //   additional: Pointer to the additional data
+  //   additional_length: Length of the additional data
+  //   add_id: Value of BlockAddID element
+  //   track_number: Track to add the data to. Value returned by Add track
+  //                 functions.  The range of allowed values is [1, 126].
+  //   abs_timecode: Absolute (not relative to cluster) timestamp of the
+  //                 frame, expressed in timecode units.
+  //   is_key:       Flag telling whether or not this frame is a key frame.
+  bool AddFrameWithAdditional(const uint8* frame,
+                              uint64 length,
+                              const uint8* additional,
+                              uint64 additional_length,
+                              uint64 add_id,
+                              uint64 track_number,
+                              uint64 abs_timecode,
+                              bool is_key);
+
+  // Adds a frame to be output in the file. The frame is written out through
+  // |writer_| if successful. Returns true on success.
+  // Inputs:
+  //   frame: Pointer to the data.
+  //   length: Length of the data.
+  //   discard_padding: DiscardPadding element value.
+  //   track_number: Track to add the data to. Value returned by Add track
+  //                 functions.  The range of allowed values is [1, 126].
+  //   abs_timecode: Absolute (not relative to cluster) timestamp of the
+  //                 frame, expressed in timecode units.
+  //   is_key:       Flag telling whether or not this frame is a key frame.
+  bool AddFrameWithDiscardPadding(const uint8* frame,
+                                  uint64 length,
+                                  int64 discard_padding,
+                                  uint64 track_number,
+                                  uint64 abs_timecode,
+                                  bool is_key);
+
+  // Writes a frame of metadata to the output medium; returns true on
+  // success.
+  // Inputs:
+  //   frame: Pointer to the data
+  //   length: Length of the data
+  //   track_number: Track to add the data to. Value returned by Add track
+  //                 functions.  The range of allowed values is [1, 126].
+  //   timecode:     Absolute (not relative to cluster) timestamp of the
+  //                 metadata frame, expressed in timecode units.
+  //   duration:     Duration of metadata frame, in timecode units.
+  //
+  // The metadata frame is written as a block group, with a duration
+  // sub-element but no reference time sub-elements (indicating that
+  // it is considered a keyframe, per Matroska semantics).
+  bool AddMetadata(const uint8* frame,
+                   uint64 length,
+                   uint64 track_number,
+                   uint64 timecode,  // timecode units (absolute)
+                   uint64 duration);  // timecode units
+
+  // Increments the size of the cluster's data in bytes.
+  void AddPayloadSize(uint64 size);
+
+  // Closes the cluster so no more data can be written to it. Will update the
+  // cluster's size if |writer_| is seekable. Returns true on success.
+  bool Finalize();
+
+  // Returns the size in bytes for the entire Cluster element.
+  uint64 Size() const;
+
+  int64 size_position() const { return size_position_; }
+  int32 blocks_added() const { return blocks_added_; }
+  uint64 payload_size() const { return payload_size_; }
+  int64 position_for_cues() const { return position_for_cues_; }
+  uint64 timecode() const { return timecode_; }
+
+ private:
+  //  Signature that matches either of WriteSimpleBlock or WriteMetadataBlock
+  //  in the muxer utilities package.
+  typedef uint64 (*WriteBlock)(IMkvWriter* writer,
+                               const uint8* data,
+                               uint64 length,
+                               uint64 track_number,
+                               int64 timecode,
+                               uint64 generic_arg);
+
+  //  Signature that matches WriteBlockWithAdditional
+  //  in the muxer utilities package.
+  typedef uint64 (*WriteBlockAdditional)(IMkvWriter* writer,
+                                         const uint8* data,
+                                         uint64 length,
+                                         const uint8* additional,
+                                         uint64 add_id,
+                                         uint64 additional_length,
+                                         uint64 track_number,
+                                         int64 timecode,
+                                         uint64 is_key);
+
+  //  Signature that matches WriteBlockWithDiscardPadding
+  //  in the muxer utilities package.
+  typedef uint64 (*WriteBlockDiscardPadding)(IMkvWriter* writer,
+                                             const uint8* data,
+                                             uint64 length,
+                                             int64 discard_padding,
+                                             uint64 track_number,
+                                             int64 timecode,
+                                             uint64 is_key);
+
+  // Utility method that confirms that blocks can still be added, and that the
+  // cluster header has been written. Used by |DoWriteBlock*|. Returns true
+  // when successful.
+  template <typename Type>
+  bool PreWriteBlock(Type* write_function);
+
+  // Utility method used by the |DoWriteBlock*| methods that handles the book
+  // keeping required after each block is written.
+  void PostWriteBlock(uint64 element_size);
+
+  // To simplify things, we require that there be fewer than 127
+  // tracks -- this allows us to serialize the track number value for
+  // a stream using a single byte, per the Matroska encoding.
+  bool IsValidTrackNumber(uint64 track_number) const;
+
+  // Given |abs_timecode|, calculates timecode relative to most recent timecode.
+  // Returns -1 on failure, or a relative timecode.
+  int64 GetRelativeTimecode(int64 abs_timecode) const;
+
+  //  Used to implement AddFrame and AddMetadata.
+  bool DoWriteBlock(const uint8* frame,
+                    uint64 length,
+                    uint64 track_number,
+                    uint64 absolute_timecode,
+                    uint64 generic_arg,
+                    WriteBlock write_block);
+
+  // Used to implement AddFrameWithAdditional
+  bool DoWriteBlockWithAdditional(const uint8* frame,
+                                  uint64 length,
+                                  const uint8* additional,
+                                  uint64 additional_length,
+                                  uint64 add_id,
+                                  uint64 track_number,
+                                  uint64 absolute_timecode,
+                                  uint64 generic_arg,
+                                  WriteBlockAdditional write_block);
+
+  // Used to implement AddFrameWithDiscardPadding
+  bool DoWriteBlockWithDiscardPadding(const uint8* frame,
+                                      uint64 length,
+                                      int64 discard_padding,
+                                      uint64 track_number,
+                                      uint64 absolute_timecode,
+                                      uint64 generic_arg,
+                                      WriteBlockDiscardPadding write_block);
+
+  // Outputs the Cluster header to |writer_|. Returns true on success.
+  bool WriteClusterHeader();
+
+  // Number of blocks added to the cluster.
+  int32 blocks_added_;
+
+  // Flag telling if the cluster has been closed.
+  bool finalized_;
+
+  // Flag telling if the cluster's header has been written.
+  bool header_written_;
+
+  // The size of the cluster elements in bytes.
+  uint64 payload_size_;
+
+  // The file position used for cue points.
+  const int64 position_for_cues_;
+
+  // The file position of the cluster's size element.
+  int64 size_position_;
+
+  // The absolute timecode of the cluster.
+  const uint64 timecode_;
+
+  // Pointer to the writer object. Not owned by this class.
+  IMkvWriter* writer_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(Cluster);
+};
+
+///////////////////////////////////////////////////////////////
+// SeekHead element
+class SeekHead {
+ public:
+  SeekHead();
+  ~SeekHead();
+
+  // TODO(fgalligan): Change this to reserve a certain size. Then check how
+  // big the seek entry to be added is as not every seek entry will be the
+  // maximum size it could be.
+  // Adds a seek entry to be written out when the element is finalized. |id|
+  // must be the coded mkv element id. |pos| is the file position of the
+  // element. Returns true on success.
+  bool AddSeekEntry(uint32 id, uint64 pos);
+
+  // Writes out SeekHead and SeekEntry elements. Returns true on success.
+  bool Finalize(IMkvWriter* writer) const;
+
+  // Returns the id of the Seek Entry at the given index. Returns -1 if index is
+  // out of range.
+  uint32 GetId(int index) const;
+
+  // Returns the position of the Seek Entry at the given index. Returns -1 if
+  // index is out of range.
+  uint64 GetPosition(int index) const;
+
+  // Sets the Seek Entry id and position at given index.
+  // Returns true on success.
+  bool SetSeekEntry(int index, uint32 id, uint64 position);
+
+  // Reserves space by writing out a Void element which will be updated with
+  // a SeekHead element later. Returns true on success.
+  bool Write(IMkvWriter* writer);
+
+  // We are going to put a cap on the number of Seek Entries.
+  const static int32 kSeekEntryCount = 5;
+
+ private:
+  // Returns the maximum size in bytes of one seek entry.
+  uint64 MaxEntrySize() const;
+
+  // Seek entry id element list.
+  uint32 seek_entry_id_[kSeekEntryCount];
+
+  // Seek entry pos element list.
+  uint64 seek_entry_pos_[kSeekEntryCount];
+
+  // The file position of SeekHead element.
+  int64 start_pos_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(SeekHead);
+};
+
+///////////////////////////////////////////////////////////////
+// Segment Information element
+class SegmentInfo {
+ public:
+  SegmentInfo();
+  ~SegmentInfo();
+
+  // Will update the duration if |duration_| is > 0.0. Returns true on success.
+  bool Finalize(IMkvWriter* writer) const;
+
+  // Sets |muxing_app_| and |writing_app_|.
+  bool Init();
+
+  // Output the Segment Information element to the writer. Returns true on
+  // success.
+  bool Write(IMkvWriter* writer);
+
+  void set_duration(double duration) { duration_ = duration; }
+  double duration() const { return duration_; }
+  void set_muxing_app(const char* app);
+  const char* muxing_app() const { return muxing_app_; }
+  void set_timecode_scale(uint64 scale) { timecode_scale_ = scale; }
+  uint64 timecode_scale() const { return timecode_scale_; }
+  void set_writing_app(const char* app);
+  const char* writing_app() const { return writing_app_; }
+
+ private:
+  // Segment Information element names.
+  // Initially set to -1 to signify that a duration has not been set and should
+  // not be written out.
+  double duration_;
+  // Set to libwebm-%d.%d.%d.%d, major, minor, build, revision.
+  char* muxing_app_;
+  uint64 timecode_scale_;
+  // Initially set to libwebm-%d.%d.%d.%d, major, minor, build, revision.
+  char* writing_app_;
+
+  // The file position of the duration element.
+  int64 duration_pos_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(SegmentInfo);
+};
+
+///////////////////////////////////////////////////////////////
+// This class represents the main segment in a WebM file. Currently only
+// supports one Segment element.
+//
+// Notes:
+//  |Init| must be called before any other method in this class.
+class Segment {
+ public:
+  enum Mode {
+    kLive = 0x1,
+    kFile = 0x2
+  };
+
+  enum CuesPosition {
+    kAfterClusters = 0x0,  // Position Cues after Clusters - Default
+    kBeforeClusters = 0x1  // Position Cues before Clusters
+  };
+
+  const static uint64 kDefaultMaxClusterDuration = 30000000000ULL;
+
+  Segment();
+  ~Segment();
+
+  // Initializes |SegmentInfo| and returns result. Always returns false when
+  // |ptr_writer| is NULL.
+  bool Init(IMkvWriter* ptr_writer);
+
+  // Adds a generic track to the segment.  Returns the newly-allocated
+  // track object (which is owned by the segment) on success, NULL on
+  // error. |number| is the number to use for the track.  |number|
+  // must be >= 0. If |number| == 0 then the muxer will decide on the
+  // track number.
+  Track* AddTrack(int32 number);
+
+  // Adds a Vorbis audio track to the segment. Returns the number of the track
+  // on success, 0 on error. |number| is the number to use for the audio track.
+  // |number| must be >= 0. If |number| == 0 then the muxer will decide on
+  // the track number.
+  uint64 AddAudioTrack(int32 sample_rate, int32 channels, int32 number);
+
+  // Adds an empty chapter to the chapters of this segment.  Returns
+  // non-NULL on success.  After adding the chapter, the caller should
+  // populate its fields via the Chapter member functions.
+  Chapter* AddChapter();
+
+  // Adds a cue point to the Cues element. |timestamp| is the time in
+  // nanoseconds of the cue's time. |track| is the Track of the Cue. This
+  // function must be called after AddFrame to calculate the correct
+  // BlockNumber for the CuePoint. Returns true on success.
+  bool AddCuePoint(uint64 timestamp, uint64 track);
+
+  // Adds a frame to be output in the file. Returns true on success.
+  // Inputs:
+  //   frame: Pointer to the data
+  //   length: Length of the data
+  //   track_number: Track to add the data to. Value returned by Add track
+  //                 functions.
+  //   timestamp:    Timestamp of the frame in nanoseconds from 0.
+  //   is_key:       Flag telling whether or not this frame is a key frame.
+  bool AddFrame(const uint8* frame,
+                uint64 length,
+                uint64 track_number,
+                uint64 timestamp_ns,
+                bool is_key);
+
+  // Writes a frame of metadata to the output medium; returns true on
+  // success.
+  // Inputs:
+  //   frame: Pointer to the data
+  //   length: Length of the data
+  //   track_number: Track to add the data to. Value returned by Add track
+  //                 functions.
+  //   timecode:     Absolute timestamp of the metadata frame, expressed
+  //                 in nanosecond units.
+  //   duration:     Duration of metadata frame, in nanosecond units.
+  //
+  // The metadata frame is written as a block group, with a duration
+  // sub-element but no reference time sub-elements (indicating that
+  // it is considered a keyframe, per Matroska semantics).
+  bool AddMetadata(const uint8* frame,
+                   uint64 length,
+                   uint64 track_number,
+                   uint64 timestamp_ns,
+                   uint64 duration_ns);
+
+  // Writes a frame with additional data to the output medium; returns true on
+  // success.
+  // Inputs:
+  //   frame: Pointer to the data.
+  //   length: Length of the data.
+  //   additional: Pointer to additional data.
+  //   additional_length: Length of additional data.
+  //   add_id: Additional ID which identifies the type of additional data.
+  //   track_number: Track to add the data to. Value returned by Add track
+  //                 functions.
+  //   timestamp:    Absolute timestamp of the frame, expressed in nanosecond
+  //                 units.
+  //   is_key:       Flag telling whether or not this frame is a key frame.
+  bool AddFrameWithAdditional(const uint8* frame,
+                              uint64 length,
+                              const uint8* additional,
+                              uint64 additional_length,
+                              uint64 add_id,
+                              uint64 track_number,
+                              uint64 timestamp,
+                              bool is_key);
+
+  // Writes a frame with DiscardPadding to the output medium; returns true on
+  // success.
+  // Inputs:
+  //   frame: Pointer to the data.
+  //   length: Length of the data.
+  //   discard_padding: DiscardPadding element value.
+  //   track_number: Track to add the data to. Value returned by Add track
+  //                 functions.
+  //   timestamp:    Absolute timestamp of the frame, expressed in nanosecond
+  //                 units.
+  //   is_key:       Flag telling whether or not this frame is a key frame.
+  bool AddFrameWithDiscardPadding(const uint8* frame,
+                                  uint64 length,
+                                  int64 discard_padding,
+                                  uint64 track_number,
+                                  uint64 timestamp,
+                                  bool is_key);
+
+  // Writes a Frame to the output medium. Chooses the correct way of writing
+  // the frame (Block vs SimpleBlock) based on the parameters passed.
+  // Inputs:
+  //   frame: frame object
+  bool AddGenericFrame(const Frame* frame);
+
+  // Adds a VP8 video track to the segment. Returns the number of the track on
+  // success, 0 on error. |number| is the number to use for the video track.
+  // |number| must be >= 0. If |number| == 0 then the muxer will decide on
+  // the track number.
+  uint64 AddVideoTrack(int32 width, int32 height, int32 number);
+
+  // This function must be called after Finalize() if you need a copy of the
+  // output with Cues written before the Clusters. It will return false if the
+  // writer is not seekable of if chunking is set to true.
+  // Input parameters:
+  // reader - an IMkvReader object created with the same underlying file of the
+  //          current writer object. Make sure to close the existing writer
+  //          object before creating this so that all the data is properly
+  //          flushed and available for reading.
+  // writer - an IMkvWriter object pointing to a *different* file than the one
+  //          pointed by the current writer object. This file will contain the
+  //          Cues element before the Clusters.
+  bool CopyAndMoveCuesBeforeClusters(mkvparser::IMkvReader* reader,
+                                     IMkvWriter* writer);
+
+  // Sets which track to use for the Cues element. Must have added the track
+  // before calling this function. Returns true on success. |track_number| is
+  // returned by the Add track functions.
+  bool CuesTrack(uint64 track_number);
+
+  // This will force the muxer to create a new Cluster when the next frame is
+  // added.
+  void ForceNewClusterOnNextFrame();
+
+  // Writes out any frames that have not been written out. Finalizes the last
+  // cluster. May update the size and duration of the segment. May output the
+  // Cues element. May finalize the SeekHead element. Returns true on success.
+  bool Finalize();
+
+  // Returns the Cues object.
+  Cues* GetCues() { return &cues_; }
+
+  // Returns the Segment Information object.
+  const SegmentInfo* GetSegmentInfo() const { return &segment_info_; }
+  SegmentInfo* GetSegmentInfo() { return &segment_info_; }
+
+  // Search the Tracks and return the track that matches |track_number|.
+  // Returns NULL if there is no track match.
+  Track* GetTrackByNumber(uint64 track_number) const;
+
+  // Toggles whether to output a cues element.
+  void OutputCues(bool output_cues);
+
+  // Sets if the muxer will output files in chunks or not. |chunking| is a
+  // flag telling whether or not to turn on chunking. |filename| is the base
+  // filename for the chunk files. The header chunk file will be named
+  // |filename|.hdr and the data chunks will be named
+  // |filename|_XXXXXX.chk. Chunking implies that the muxer will be writing
+  // to files so the muxer will use the default MkvWriter class to control
+  // what data is written to what files. Returns true on success.
+  // TODO: Should we change the IMkvWriter Interface to add Open and Close?
+  // That will force the interface to be dependent on files.
+  bool SetChunking(bool chunking, const char* filename);
+
+  bool chunking() const { return chunking_; }
+  uint64 cues_track() const { return cues_track_; }
+  void set_max_cluster_duration(uint64 max_cluster_duration) {
+    max_cluster_duration_ = max_cluster_duration;
+  }
+  uint64 max_cluster_duration() const { return max_cluster_duration_; }
+  void set_max_cluster_size(uint64 max_cluster_size) {
+    max_cluster_size_ = max_cluster_size;
+  }
+  uint64 max_cluster_size() const { return max_cluster_size_; }
+  void set_mode(Mode mode) { mode_ = mode; }
+  Mode mode() const { return mode_; }
+  CuesPosition cues_position() const { return cues_position_; }
+  bool output_cues() const { return output_cues_; }
+  const SegmentInfo* segment_info() const { return &segment_info_; }
+
+ private:
+  // Checks if header information has been output and initialized. If not it
+  // will output the Segment element and initialize the SeekHead elment and
+  // Cues elements.
+  bool CheckHeaderInfo();
+
+  // Sets |name| according to how many chunks have been written. |ext| is the
+  // file extension. |name| must be deleted by the calling app. Returns true
+  // on success.
+  bool UpdateChunkName(const char* ext, char** name) const;
+
+  // Returns the maximum offset within the segment's payload. When chunking
+  // this function is needed to determine offsets of elements within the
+  // chunked files. Returns -1 on error.
+  int64 MaxOffset();
+
+  // Adds the frame to our frame array.
+  bool QueueFrame(Frame* frame);
+
+  // Output all frames that are queued. Returns -1 on error, otherwise
+  // it returns the number of frames written.
+  int WriteFramesAll();
+
+  // Output all frames that are queued that have an end time that is less
+  // then |timestamp|. Returns true on success and if there are no frames
+  // queued.
+  bool WriteFramesLessThan(uint64 timestamp);
+
+  // Outputs the segment header, Segment Information element, SeekHead element,
+  // and Tracks element to |writer_|.
+  bool WriteSegmentHeader();
+
+  // Given a frame with the specified timestamp (nanosecond units) and
+  // keyframe status, determine whether a new cluster should be
+  // created, before writing enqueued frames and the frame itself. The
+  // function returns one of the following values:
+  //  -1 = error: an out-of-order frame was detected
+  //  0 = do not create a new cluster, and write frame to the existing cluster
+  //  1 = create a new cluster, and write frame to that new cluster
+  //  2 = create a new cluster, and re-run test
+  int TestFrame(uint64 track_num, uint64 timestamp_ns, bool key) const;
+
+  // Create a new cluster, using the earlier of the first enqueued
+  // frame, or the indicated time. Returns true on success.
+  bool MakeNewCluster(uint64 timestamp_ns);
+
+  // Checks whether a new cluster needs to be created, and if so
+  // creates a new cluster. Returns false if creation of a new cluster
+  // was necessary but creation was not successful.
+  bool DoNewClusterProcessing(uint64 track_num, uint64 timestamp_ns, bool key);
+
+
+  // Adjusts Cue Point values (to place Cues before Clusters) so that they
+  // reflect the correct offsets.
+  void MoveCuesBeforeClusters();
+
+  // This function recursively computes the correct cluster offsets (this is
+  // done to move the Cues before Clusters). It recursively updates the change
+  // in size (which indicates a change in cluster offset) until no sizes change.
+  // Parameters:
+  // diff - indicates the difference in size of the Cues element that needs to
+  //        accounted for.
+  // index - index in the list of Cues which is currently being adjusted.
+  // cue_size - size of the Cues element.
+  void MoveCuesBeforeClustersHelper(uint64 diff, int index, uint64* cue_size);
+
+  // Seeds the random number generator used to make UIDs.
+  unsigned int seed_;
+
+  // WebM elements
+  Cues cues_;
+  SeekHead seek_head_;
+  SegmentInfo segment_info_;
+  Tracks tracks_;
+  Chapters chapters_;
+
+  // Number of chunks written.
+  int chunk_count_;
+
+  // Current chunk filename.
+  char* chunk_name_;
+
+  // Default MkvWriter object created by this class used for writing clusters
+  // out in separate files.
+  MkvWriter* chunk_writer_cluster_;
+
+  // Default MkvWriter object created by this class used for writing Cues
+  // element out to a file.
+  MkvWriter* chunk_writer_cues_;
+
+  // Default MkvWriter object created by this class used for writing the
+  // Matroska header out to a file.
+  MkvWriter* chunk_writer_header_;
+
+  // Flag telling whether or not the muxer is chunking output to multiple
+  // files.
+  bool chunking_;
+
+  // Base filename for the chunked files.
+  char* chunking_base_name_;
+
+  // File position offset where the Clusters end.
+  int64 cluster_end_offset_;
+
+  // List of clusters.
+  Cluster** cluster_list_;
+
+  // Number of cluster pointers allocated in the cluster list.
+  int32 cluster_list_capacity_;
+
+  // Number of clusters in the cluster list.
+  int32 cluster_list_size_;
+
+  // Indicates whether Cues should be written before or after Clusters
+  CuesPosition cues_position_;
+
+  // Track number that is associated with the cues element for this segment.
+  uint64 cues_track_;
+
+  // Tells the muxer to force a new cluster on the next Block.
+  bool force_new_cluster_;
+
+  // List of stored audio frames. These variables are used to store frames so
+  // the muxer can follow the guideline "Audio blocks that contain the video
+  // key frame's timecode should be in the same cluster as the video key frame
+  // block."
+  Frame** frames_;
+
+  // Number of frame pointers allocated in the frame list.
+  int32 frames_capacity_;
+
+  // Number of frames in the frame list.
+  int32 frames_size_;
+
+  // Flag telling if a video track has been added to the segment.
+  bool has_video_;
+
+  // Flag telling if the segment's header has been written.
+  bool header_written_;
+
+  // Duration of the last block in nanoseconds.
+  uint64 last_block_duration_;
+
+  // Last timestamp in nanoseconds added to a cluster.
+  uint64 last_timestamp_;
+
+  // Maximum time in nanoseconds for a cluster duration. This variable is a
+  // guideline and some clusters may have a longer duration. Default is 30
+  // seconds.
+  uint64 max_cluster_duration_;
+
+  // Maximum size in bytes for a cluster. This variable is a guideline and
+  // some clusters may have a larger size. Default is 0 which signifies that
+  // the muxer will decide the size.
+  uint64 max_cluster_size_;
+
+  // The mode that segment is in. If set to |kLive| the writer must not
+  // seek backwards.
+  Mode mode_;
+
+  // Flag telling the muxer that a new cue point should be added.
+  bool new_cuepoint_;
+
+  // TODO(fgalligan): Should we add support for more than one Cues element?
+  // Flag whether or not the muxer should output a Cues element.
+  bool output_cues_;
+
+  // The file position of the segment's payload.
+  int64 payload_pos_;
+
+  // The file position of the element's size.
+  int64 size_position_;
+
+  // Pointer to the writer objects. Not owned by this class.
+  IMkvWriter* writer_cluster_;
+  IMkvWriter* writer_cues_;
+  IMkvWriter* writer_header_;
+
+  LIBWEBM_DISALLOW_COPY_AND_ASSIGN(Segment);
+};
+
+}  //end namespace mkvmuxer
+
+#endif //MKVMUXER_HPP