FFmpeg/libavutil/downmix_info.h

/*
 * Copyright (c) 2014 Tim Walker <tdskywalker@gmail.com>
 *
 * This file is part of Libav.
 *
 * Libav 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.
 *
 * Libav 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 Libav; 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.
 *
 * The side data is created and added to the frame if it's absent.
 *
 * @param frame the frame for which the side data is to be obtained.
 *
 * @return the AVDownmixInfo structure to be edited by the caller.
 */
AVDownmixInfo *av_downmix_info_update_side_data(AVFrame *frame);

/**
 * @}
 */

/**
 * @}
 */

#endif /* AVUTIL_DOWNMIX_INFO_H */