text: /*
   * Copyright (c) 2014 Tim Walker <tdskywalker@gmail.com>
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #ifndef AVUTIL_DOWNMIX_INFO_H
  #define AVUTIL_DOWNMIX_INFO_H
  
  #include "frame.h"
  
  /**
   * @file
   * audio downmix medatata
   */
  
  /**
   * @addtogroup lavu_audio
   * @{
   */
  
  /**
   * @defgroup downmix_info Audio downmix metadata
   * @{
   */
  
  /**
   * Possible downmix types.
   */
  enum AVDownmixType {
      AV_DOWNMIX_TYPE_UNKNOWN, /**< Not indicated. */
      AV_DOWNMIX_TYPE_LORO,    /**< Lo/Ro 2-channel downmix (Stereo). */
      AV_DOWNMIX_TYPE_LTRT,    /**< Lt/Rt 2-channel downmix, Dolby Surround compatible. */
      AV_DOWNMIX_TYPE_DPLII,   /**< Lt/Rt 2-channel downmix, Dolby Pro Logic II compatible. */
      AV_DOWNMIX_TYPE_NB       /**< Number of downmix types. Not part of ABI. */
  };
  
  /**
   * This structure describes optional metadata relevant to a downmix procedure.
   *
   * All fields are set by the decoder to the value indicated in the audio
   * bitstream (if present), or to a "sane" default otherwise.
   */
  typedef struct AVDownmixInfo {
      /**
       * Type of downmix preferred by the mastering engineer.
       */
      enum AVDownmixType preferred_downmix_type;
  
      /**
       * Absolute scale factor representing the nominal level of the center
       * channel during a regular downmix.
       */
      double center_mix_level;
  
      /**
       * Absolute scale factor representing the nominal level of the center
       * channel during an Lt/Rt compatible downmix.
       */
      double center_mix_level_ltrt;
  
      /**
       * Absolute scale factor representing the nominal level of the surround
       * channels during a regular downmix.
       */
      double surround_mix_level;
  
      /**
       * Absolute scale factor representing the nominal level of the surround
       * channels during an Lt/Rt compatible downmix.
       */
      double surround_mix_level_ltrt;
  
      /**
       * Absolute scale factor representing the level at which the LFE data is
       * mixed into L/R channels during downmixing.
       */
      double lfe_mix_level;
  } AVDownmixInfo;
  
  /**
   * Get a frame's AV_FRAME_DATA_DOWNMIX_INFO side data for editing.
   *
   * If the side data is absent, it is created and added to the frame.
   *
   * @param frame the frame for which the side data is to be obtained or created
   *
   * @return the AVDownmixInfo structure to be edited by the caller, or NULL if
   *         the structure cannot be allocated.
   */
  AVDownmixInfo *av_downmix_info_update_side_data(AVFrame *frame);
  
  /**
   * @}
   */
  
  /**
   * @}
   */
  
  #endif /* AVUTIL_DOWNMIX_INFO_H */
  