---------------------------------------------------------------------
audacious-3.9/src/libaudcore/audio.h

### BEFORE ###
struct ReplayGainInfo {
    float track_gain; /* dB */
    float track_peak; /* 0-1 */
    float album_gain; /* dB */
    float album_peak; /* 0-1 */
};

### AFTER ###
struct ReplayGainInfo {
    float track_gain; /* dB */
    float track_peak; /* 0-1 */
    float album_gain; /* dB */
    float album_peak; /* 0-1 */
    int track_gain_is_set; /* true or false */
    int album_gain_is_set; /* true or false */
};

---------------------------------------------------------------------
audacious-3.9/src/libaudcore/tuple.cc

### BEFORE ###
EXPORT ReplayGainInfo Tuple::get_replay_gain () const
{
    ReplayGainInfo gain {};
[…]
    return gain;
}

### AFTER ###
EXPORT ReplayGainInfo Tuple::get_replay_gain () const
{
    ReplayGainInfo gain {};
[…]
    gain.album_gain_is_set = (data->is_set (AlbumGain)) ? 1 : 0;
    gain.track_gain_is_set = (data->is_set (TrackGain)) ? 1 : 0;

    return gain;
}

---------------------------------------------------------------------
audacious-3.9/src/libaudcore/output.cc

### BEFORE ###
static bool s_gain; /* replay gain info set */

### AFTER ###
// line removed


### BEFORE ###
static void apply_replay_gain (Index<float> & data)
{
    if (! aud_get_bool (0, "enable_replay_gain"))
        return;

    float factor = powf (10, aud_get_double (0, "replay_gain_preamp") / 20);

    if (s_gain)
    {
        float peak;

        auto mode = (ReplayGainMode) aud_get_int (0, "replay_gain_mode");
        if ((mode == ReplayGainMode::Album) ||
            (mode == ReplayGainMode::Automatic &&
             (! aud_get_bool (0, "shuffle") || aud_get_bool (0, "album_shuffle"))))
        {
            factor *= powf (10, gain_info.album_gain / 20);
            peak = gain_info.album_peak;
        }
        else
        {
            factor *= powf (10, gain_info.track_gain / 20);
            peak = gain_info.track_peak;
        }

        if (aud_get_bool (0, "enable_clipping_prevention") && peak * factor > 1)
            factor = 1 / peak;
    }
    else
        factor *= powf (10, aud_get_double (0, "default_gain") / 20);

    if (factor < 0.99 || factor > 1.01)
        audio_amplify (data.begin (), 1, data.len (), & factor);
}

### AFTER ###
static void apply_replay_gain (Index<float> & data)
{
    if (! aud_get_bool (0, "enable_replay_gain"))
        return;

    float factor = powf (10, aud_get_double (0, "replay_gain_preamp") / 20);
    float peak;
    auto mode = (ReplayGainMode) aud_get_int (0, "replay_gain_mode");
    if (
        ((mode == ReplayGainMode::Album) ||
         (mode == ReplayGainMode::Automatic &&
          (! aud_get_bool (0, "shuffle") || aud_get_bool (0, "album_shuffle")))) &&
           (gain_info.album_gain_is_set))
    {
        factor *= powf (10, gain_info.album_gain / 20);
        peak = gain_info.album_peak;
        if (aud_get_bool (0, "enable_clipping_prevention") && peak * factor > 1)
            factor = 1 / peak;
    }
    else
    {
        if (gain_info.track_gain_is_set)
        {
            factor *= powf (10, gain_info.track_gain / 20);
            peak = gain_info.track_peak;
            if (aud_get_bool (0, "enable_clipping_prevention") && peak * factor > 1)
                factor = 1 / peak;
        }
        else
            factor *= powf (10, aud_get_double (0, "default_gain") / 20);
    }

    if (factor < 0.99 || factor > 1.01)
        audio_amplify (data.begin (), 1, data.len (), & factor);
}


### BEFORE ###
    s_gain = s_paused = s_flushed = false;

### AFTER ###
    s_paused = s_flushed = false;

### BEFORE ###
        s_gain = true;

### AFTER ###
        // line removed

---------------------------------------------------------------------
src/vorbis/vorbis.cc

### BEFORE ###
static bool update_replay_gain (OggVorbis_File * vf, ReplayGainInfo * rg_info)
{
    const char *rg_gain, *rg_peak;

    vorbis_comment * comment = ov_comment (vf, -1);
    if (! comment)
        return false;

    rg_gain = vorbis_comment_query(comment, "REPLAYGAIN_ALBUM_GAIN", 0);
    if (!rg_gain) rg_gain = vorbis_comment_query(comment, "RG_AUDIOPHILE", 0);    /* Old */
    rg_info->album_gain = (rg_gain != nullptr) ? str_to_double (rg_gain) : 0.0;
    AUDDBG ("Album gain: %s (%f)\n", rg_gain, rg_info->album_gain);

    rg_gain = vorbis_comment_query(comment, "REPLAYGAIN_TRACK_GAIN", 0);
    if (!rg_gain) rg_gain = vorbis_comment_query(comment, "RG_RADIO", 0);    /* Old */
    rg_info->track_gain = (rg_gain != nullptr) ? str_to_double (rg_gain) : 0.0;
    AUDDBG ("Track gain: %s (%f)\n", rg_gain, rg_info->track_gain);

    rg_peak = vorbis_comment_query(comment, "REPLAYGAIN_ALBUM_PEAK", 0);
    rg_info->album_peak = rg_peak != nullptr ? str_to_double (rg_peak) : 0.0;
    AUDDBG ("Album peak: %s (%f)\n", rg_peak, rg_info->album_peak);

    rg_peak = vorbis_comment_query(comment, "REPLAYGAIN_TRACK_PEAK", 0);
    if (!rg_peak) rg_peak = vorbis_comment_query(comment, "RG_PEAK", 0);  /* Old */
    rg_info->track_peak = rg_peak != nullptr ? str_to_double (rg_peak) : 0.0;
    AUDDBG ("Track peak: %s (%f)\n", rg_peak, rg_info->track_peak);


    return true;
}

### AFTER ###
static bool update_replay_gain (OggVorbis_File * vf, ReplayGainInfo * rg_info)
{
    const char *rg_gain, *rg_peak;

    vorbis_comment * comment = ov_comment (vf, -1);
    if (! comment)
        return false;

    rg_gain = vorbis_comment_query(comment, "REPLAYGAIN_ALBUM_GAIN", 0);
    if (!rg_gain) rg_gain = vorbis_comment_query(comment, "RG_AUDIOPHILE", 0);    /* Old */
    rg_info->album_gain = (rg_gain != nullptr) ? str_to_double (rg_gain) : 0.0;
    AUDDBG ("Album gain: %s (%f)\n", rg_gain, rg_info->album_gain);
    rg_info->album_gain_is_set = (rg_gain != nullptr) ? 1 : 0;

    rg_gain = vorbis_comment_query(comment, "REPLAYGAIN_TRACK_GAIN", 0);
    if (!rg_gain) rg_gain = vorbis_comment_query(comment, "RG_RADIO", 0);    /* Old */
    rg_info->track_gain = (rg_gain != nullptr) ? str_to_double (rg_gain) : 0.0;
    AUDDBG ("Track gain: %s (%f)\n", rg_gain, rg_info->track_gain);
    rg_info->track_gain_is_set = (rg_gain != nullptr) ? 1 : 0;

    rg_peak = vorbis_comment_query(comment, "REPLAYGAIN_ALBUM_PEAK", 0);
    rg_info->album_peak = rg_peak != nullptr ? str_to_double (rg_peak) : 0.0;
    AUDDBG ("Album peak: %s (%f)\n", rg_peak, rg_info->album_peak);

    rg_peak = vorbis_comment_query(comment, "REPLAYGAIN_TRACK_PEAK", 0);
    if (!rg_peak) rg_peak = vorbis_comment_query(comment, "RG_PEAK", 0);  /* Old */
    rg_info->track_peak = rg_peak != nullptr ? str_to_double (rg_peak) : 0.0;
    AUDDBG ("Track peak: %s (%f)\n", rg_peak, rg_info->track_peak);


    return true;
}
---------------------------------------------------------------------