/*****************************************************************************
 * compressor.c: dynamic range compressor, ported from plugins from LADSPA SWH
 *****************************************************************************
 * Copyright (C) 2010 Ronald Wright
 * $Id$
 *
 * Author: Ronald Wright <logiconcepts819@gmail.com>
 * Original author: Steve Harris <steve@plugin.org.uk>
 *
 * This program 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.
 *
 * This program 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 this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <math.h>
#include <stdint.h>

#include <vlc_common.h>
#include <vlc_plugin.h>

#include <vlc_aout.h>
#include <vlc_filter.h>

/*****************************************************************************
* Local prototypes.
*****************************************************************************/

#define A_TBL (256)

#define DB_TABLE_SIZE   (1024)
#define DB_MIN          (-60.0f)
#define DB_MAX          (24.0f)
#define LIN_TABLE_SIZE  (1024)
#define LIN_MIN         (0.0000000002f)
#define LIN_MAX         (9.0f)
#define DB_DEFAULT_CUBE
#define RMS_BUF_SIZE    (960)
#define LOOKAHEAD_SIZE  ((RMS_BUF_SIZE)<<1)

#define LIN_INTERP(f,a,b) ((a) + (f) * ( (b) - (a) ))
#define LIMIT(v,l,u)      (v < l ? l : ( v > u ? u : v ))

typedef struct
{
    float        pf_buf[RMS_BUF_SIZE];
    unsigned int i_pos;
    unsigned int i_count;
    float        f_sum;

} rms_env;

typedef struct
{
    struct
    {
        float pf_vals[AOUT_CHAN_MAX];
        float f_lev_in;

    } p_buf[LOOKAHEAD_SIZE];
    unsigned int i_pos;
    unsigned int i_count;

} lookahead;

struct filter_sys_t
{
    float f_amp;
    float pf_as[A_TBL];
    unsigned int i_count;
    float f_env;
    float f_env_peak;
    float f_env_rms;
    float f_gain;
    float f_gain_out;
    rms_env rms;
    float f_sum;
    lookahead la;

    float pf_db_data[DB_TABLE_SIZE];
    float pf_lin_data[LIN_TABLE_SIZE];

    vlc_mutex_t lock;

    float f_rms_peak;
    float f_attack;
    float f_release;
    float f_threshold;
    float f_ratio;
    float f_knee;
    float f_makeup_gain;
};

typedef union
{
    float f;
    int32_t i;

} ls_pcast32;

static int      Open            ( vlc_object_t * );
static void     Close           ( vlc_object_t * );
static block_t *DoWork          ( filter_t *, block_t * );

static void     DbInit          ( filter_sys_t * );
static float    Db2Lin          ( float, filter_sys_t * );
static float    Lin2Db          ( float, filter_sys_t * );
#ifdef DB_DEFAULT_CUBE
static float    CubeInterp      ( const float, const float, const float,
                                  const float, const float );
#endif
static void     RoundToZero     ( float * );
static float    Max             ( float, float );
static float    Clamp           ( float, float, float );
static int      Round           ( float );
static float    RmsEnvProcess   ( rms_env *, const float );
static void     BufferProcess   ( float *, int, float, float, lookahead * );

static int RMSPeakCallback      ( vlc_object_t *, char const *, vlc_value_t,
                                  vlc_value_t, void * );
static int AttackCallback       ( vlc_object_t *, char const *, vlc_value_t,
                                  vlc_value_t, void * );
static int ReleaseCallback      ( vlc_object_t *, char const *, vlc_value_t,
                                  vlc_value_t, void * );
static int ThresholdCallback    ( vlc_object_t *, char const *, vlc_value_t,
                                  vlc_value_t, void * );
static int RatioCallback        ( vlc_object_t *, char const *, vlc_value_t,
                                  vlc_value_t, void * );
static int KneeCallback         ( vlc_object_t *, char const *, vlc_value_t,
                                  vlc_value_t, void * );
static int MakeupGainCallback   ( vlc_object_t *, char const *, vlc_value_t,
                                  vlc_value_t, void * );

/*****************************************************************************
 * Module descriptor
 *****************************************************************************/

#define RMS_PEAK_TEXT N_( "RMS/peak" )
#define RMS_PEAK_LONGTEXT N_( "Set the RMS/peak." )

#define ATTACK_TEXT N_( "Attack time" )
#define ATTACK_LONGTEXT N_( "Set the attack time in milliseconds." )

#define RELEASE_TEXT N_( "Release time" )
#define RELEASE_LONGTEXT N_( "Set the release time in milliseconds." )

#define THRESHOLD_TEXT N_( "Threshold level" )
#define THRESHOLD_LONGTEXT N_( "Set the threshold level in dB." )

#define RATIO_TEXT N_( "Ratio" )
#define RATIO_LONGTEXT N_( "Set the ratio (n:1)." )

#define KNEE_TEXT N_( "Knee radius" )
#define KNEE_LONGTEXT N_( "Set the knee radius in dB." )

#define MAKEUP_GAIN_TEXT N_( "Makeup gain" )
#define MAKEUP_GAIN_LONGTEXT N_( "Set the makeup gain in dB (0 ... 24)." )

vlc_module_begin()
    set_shortname( N_("Compressor") )
    set_description( N_("Dynamic range compressor") )
    set_capability( "audio filter", 0 )
    set_category( CAT_AUDIO )
    set_subcategory( SUBCAT_AUDIO_AFILTER )

    add_float_with_range( "compressor-rms-peak", 0.2, 0.0, 1.0,
               RMS_PEAK_TEXT, RMS_PEAK_LONGTEXT, false )
    add_float_with_range( "compressor-attack", 25.0, 1.5, 400.0,
               ATTACK_TEXT, ATTACK_LONGTEXT, false )
    add_float_with_range( "compressor-release", 100.0, 2.0, 800.0,
               RELEASE_TEXT, RELEASE_LONGTEXT, false )
    add_float_with_range( "compressor-threshold", -11.0, -30.0, 0.0,
               THRESHOLD_TEXT, THRESHOLD_LONGTEXT, false )
    add_float_with_range( "compressor-ratio", 4.0, 1.0, 20.0,
               RATIO_TEXT, RATIO_LONGTEXT, false )
    add_float_with_range( "compressor-knee", 5.0, 1.0, 10.0,
               KNEE_TEXT, KNEE_LONGTEXT, false )
    add_float_with_range( "compressor-makeup-gain", 7.0, 0.0, 24.0,
               MAKEUP_GAIN_TEXT, MAKEUP_GAIN_LONGTEXT, false )
    set_callbacks( Open, Close )
    add_shortcut( "compressor" )
vlc_module_end ()

/*****************************************************************************
 * Open: initialize interface
 *****************************************************************************/

static int Open( vlc_object_t *p_this )
{
    filter_t *p_filter = (filter_t*)p_this;
    vlc_object_t *p_aout = p_filter->obj.parent;
    float f_sample_rate = p_filter->fmt_in.audio.i_rate;
    float f_num;

    /* Initialize the filter parameter structure */
    filter_sys_t *p_sys = p_filter->p_sys = calloc( 1, sizeof(*p_sys) );
    if( !p_sys )
    {
        return VLC_ENOMEM;
    }

    /* Initialize the attack lookup table */
    p_sys->pf_as[0] = 1.0f;
    for( int i = 1; i < A_TBL; i++ )
    {
        p_sys->pf_as[i] = expf( -1.0f / ( f_sample_rate * i / A_TBL ) );
    }

    /* Calculate the RMS and lookahead sizes from the sample rate */
    f_num = 0.01f * f_sample_rate;
    p_sys->rms.i_count = Round( Clamp( 0.5f * f_num, 1.0f, RMS_BUF_SIZE ) );
    p_sys->la.i_count = Round( Clamp( f_num, 1.0f, LOOKAHEAD_SIZE ) );

    /* Initialize decibel lookup tables */
    DbInit( p_sys );

    /* Restore the last saved settings */
    p_sys->f_rms_peak    = var_CreateGetFloat( p_aout, "compressor-rms-peak" );
    p_sys->f_attack      = var_CreateGetFloat( p_aout, "compressor-attack" );
    p_sys->f_release     = var_CreateGetFloat( p_aout, "compressor-release" );
    p_sys->f_threshold   = var_CreateGetFloat( p_aout, "compressor-threshold" );
    p_sys->f_ratio       = var_CreateGetFloat( p_aout, "compressor-ratio" );
    p_sys->f_knee        = var_CreateGetFloat( p_aout, "compressor-knee" );
    p_sys->f_makeup_gain =
           var_CreateGetFloat( p_aout, "compressor-makeup-gain" );

    /* Initialize the mutex */
    vlc_mutex_init( &p_sys->lock );

    /* Add our own callbacks */
    var_AddCallback( p_aout, "compressor-rms-peak", RMSPeakCallback, p_sys );
    var_AddCallback( p_aout, "compressor-attack", AttackCallback, p_sys );
    var_AddCallback( p_aout, "compressor-release", ReleaseCallback, p_sys );
    var_AddCallback( p_aout, "compressor-threshold", ThresholdCallback, p_sys );
    var_AddCallback( p_aout, "compressor-ratio", RatioCallback, p_sys );
    var_AddCallback( p_aout, "compressor-knee", KneeCallback, p_sys );
    var_AddCallback( p_aout, "compressor-makeup-gain", MakeupGainCallback, p_sys );

    /* Set the filter function */
    p_filter->fmt_in.audio.i_format = VLC_CODEC_FL32;
    aout_FormatPrepare(&p_filter->fmt_in.audio);
    p_filter->fmt_out.audio = p_filter->fmt_in.audio;
    p_filter->pf_audio_filter = DoWork;

    /* At this stage, we are ready! */
    msg_Dbg( p_filter, "compressor successfully initialized" );
    return VLC_SUCCESS;
}

/*****************************************************************************
 * Close: destroy interface
 *****************************************************************************/

static void Close( vlc_object_t *p_this )
{
    filter_t *p_filter = (filter_t*)p_this;
    vlc_object_t *p_aout = p_filter->obj.parent;
    filter_sys_t *p_sys = p_filter->p_sys;

    /* Remove our callbacks */
    var_DelCallback( p_aout, "compressor-rms-peak", RMSPeakCallback, p_sys );
    var_DelCallback( p_aout, "compressor-attack", AttackCallback, p_sys );
    var_DelCallback( p_aout, "compressor-release", ReleaseCallback, p_sys );
    var_DelCallback( p_aout, "compressor-threshold", ThresholdCallback, p_sys );
    var_DelCallback( p_aout, "compressor-ratio", RatioCallback, p_sys );
    var_DelCallback( p_aout, "compressor-knee", KneeCallback, p_sys );
    var_DelCallback( p_aout, "compressor-makeup-gain", MakeupGainCallback, p_sys );

    /* Destroy the mutex */
    vlc_mutex_destroy( &p_sys->lock );

    /* Destroy the filter parameter structure */
    free( p_sys );
}

/*****************************************************************************
 * DoWork: process samples buffer
 *****************************************************************************/

static block_t * DoWork( filter_t * p_filter, block_t * p_in_buf )
{
    int i_samples = p_in_buf->i_nb_samples;
    int i_channels = aout_FormatNbChannels( &p_filter->fmt_in.audio );
    float *pf_buf = (float*)p_in_buf->p_buffer;

    /* Current parameters */
    filter_sys_t *p_sys = p_filter->p_sys;

    /* Fetch the configurable parameters */
    vlc_mutex_lock( &p_sys->lock );

    float f_rms_peak    = p_sys->f_rms_peak;     /* RMS/peak */
    float f_attack      = p_sys->f_attack;       /* Attack time (ms) */
    float f_release     = p_sys->f_release;      /* Release time (ms) */
    float f_threshold   = p_sys->f_threshold;    /* Threshold level (dB) */
    float f_ratio       = p_sys->f_ratio;        /* Ratio (n:1) */
    float f_knee        = p_sys->f_knee;         /* Knee radius (dB) */
    float f_makeup_gain = p_sys->f_makeup_gain;  /* Makeup gain (dB) */

    vlc_mutex_unlock( &p_sys->lock );

    /* Fetch the internal parameters */
    float f_amp      =  p_sys->f_amp;
    float *pf_as     =  p_sys->pf_as;
    float f_env      =  p_sys->f_env;
    float f_env_peak =  p_sys->f_env_peak;
    float f_env_rms  =  p_sys->f_env_rms;
    float f_gain     =  p_sys->f_gain;
    float f_gain_out =  p_sys->f_gain_out;
    rms_env *p_rms   = &p_sys->rms;
    float f_sum      =  p_sys->f_sum;
    lookahead *p_la  = &p_sys->la;

    /* Prepare other compressor parameters */
    float f_ga       = f_attack < 2.0f ? 0.0f :
                       pf_as[Round( f_attack  * 0.001f * ( A_TBL - 1 ) )];
    float f_gr       = pf_as[Round( f_release * 0.001f * ( A_TBL - 1 ) )];
    float f_rs       = ( f_ratio - 1.0f ) / f_ratio;
    float f_mug      = Db2Lin( f_makeup_gain, p_sys );
    float f_knee_min = Db2Lin( f_threshold - f_knee, p_sys );
    float f_knee_max = Db2Lin( f_threshold + f_knee, p_sys );
    float f_ef_a     = f_ga * 0.25f;
    float f_ef_ai    = 1.0f - f_ef_a;

    /* Process the current buffer */
    for( int i = 0; i < i_samples; i++ )
    {
        float f_lev_in_old, f_lev_in_new;

        /* Now, compress the pre-equalized audio (ported from sc4_1882
         * plugin with a few modifications) */

        /* Fetch the old delayed buffer value */
        f_lev_in_old = p_la->p_buf[p_la->i_pos].f_lev_in;

        /* Find the peak value of current sample.  This becomes the new delayed
         * buffer value that replaces the old one in the lookahead array */
        f_lev_in_new = fabs( pf_buf[0] );
        for( int i_chan = 1; i_chan < i_channels; i_chan++ )
        {
            f_lev_in_new = Max( f_lev_in_new, fabs( pf_buf[i_chan] ) );
        }
        p_la->p_buf[p_la->i_pos].f_lev_in = f_lev_in_new;

        /* Add the square of the peak value to a running sum */
        f_sum += f_lev_in_new * f_lev_in_new;

        /* Update the RMS envelope */
        if( f_amp > f_env_rms )
        {
            f_env_rms = f_env_rms * f_ga + f_amp * ( 1.0f - f_ga );
        }
        else
        {
            f_env_rms = f_env_rms * f_gr + f_amp * ( 1.0f - f_gr );
        }
        RoundToZero( &f_env_rms );

        /* Update the peak envelope */
        if( f_lev_in_old > f_env_peak )
        {
            f_env_peak = f_env_peak * f_ga + f_lev_in_old * ( 1.0f - f_ga );
        }
        else
        {
            f_env_peak = f_env_peak * f_gr + f_lev_in_old * ( 1.0f - f_gr );
        }
        RoundToZero( &f_env_peak );

        /* Process the RMS value and update the output gain every 4 samples */
        if( ( p_sys->i_count++ & 3 ) == 3 )
        {
            /* Process the RMS value by placing in the mean square value, and
             * reset the running sum */
            f_amp = RmsEnvProcess( p_rms, f_sum * 0.25f );
            f_sum = 0.0f;
            if( isnan( f_env_rms ) )
            {
                /* This can happen sometimes, but I don't know why. */
                f_env_rms = 0.0f;
            }

            /* Find the superposition of the RMS and peak envelopes */
            f_env = LIN_INTERP( f_rms_peak, f_env_rms, f_env_peak );

            /* Update the output gain */
            if( f_env <= f_knee_min )
            {
                /* Gain below the knee (and below the threshold) */
                f_gain_out = 1.0f;
            }
            else if( f_env < f_knee_max )
            {
                /* Gain within the knee */
                const float f_x = -( f_threshold
                                   - f_knee - Lin2Db( f_env, p_sys ) ) / f_knee;
                f_gain_out = Db2Lin( -f_knee * f_rs * f_x * f_x * 0.25f,
                                      p_sys );
            }
            else
            {
                /* Gain above the knee (and above the threshold) */
                f_gain_out = Db2Lin( ( f_threshold - Lin2Db( f_env, p_sys ) )
                                     * f_rs, p_sys );
            }
        }

        /* Find the total gain */
        f_gain = f_gain * f_ef_a + f_gain_out * f_ef_ai;

        /* Write the resulting buffer to the output */
        BufferProcess( pf_buf, i_channels, f_gain, f_mug, p_la );
        pf_buf += i_channels;
    }

    /* Update the internal parameters */
    p_sys->f_sum      = f_sum;
    p_sys->f_amp      = f_amp;
    p_sys->f_gain     = f_gain;
    p_sys->f_gain_out = f_gain_out;
    p_sys->f_env      = f_env;
    p_sys->f_env_rms  = f_env_rms;
    p_sys->f_env_peak = f_env_peak;

    return p_in_buf;
}

/*****************************************************************************
 * Helper functions for compressor
 *****************************************************************************/

static void DbInit( filter_sys_t * p_sys )
{
    float *pf_lin_data = p_sys->pf_lin_data;
    float *pf_db_data = p_sys->pf_db_data;

    /* Fill linear lookup table */
    for( int i = 0; i < LIN_TABLE_SIZE; i++ )
    {
        pf_lin_data[i] = powf( 10.0f, ( ( DB_MAX - DB_MIN ) *
                   (float)i / LIN_TABLE_SIZE + DB_MIN ) / 20.0f );
    }

    /* Fill logarithmic lookup table */
    for( int i = 0; i < DB_TABLE_SIZE; i++ )
    {
        pf_db_data[i] = 20.0f * log10f( ( LIN_MAX - LIN_MIN ) *
                   (float)i / DB_TABLE_SIZE + LIN_MIN );
    }
}

static float Db2Lin( float f_db, filter_sys_t * p_sys )
{
    float f_scale = ( f_db - DB_MIN ) * LIN_TABLE_SIZE / ( DB_MAX - DB_MIN );
    int i_base = Round( f_scale - 0.5f );
    float f_ofs = f_scale - i_base;
    float *pf_lin_data = p_sys->pf_lin_data;

    if( i_base < 1 )
    {
        return 0.0f;
    }
    else if( i_base > LIN_TABLE_SIZE - 3 )
    {
        return pf_lin_data[LIN_TABLE_SIZE - 2];
    }

#ifdef DB_DEFAULT_CUBE
    return CubeInterp( f_ofs, pf_lin_data[i_base - 1],
                              pf_lin_data[i_base],
                              pf_lin_data[i_base + 1],
                              pf_lin_data[i_base + 2] );
#else
    return ( 1.0f - f_ofs ) * pf_lin_data[i_base]
                  + f_ofs   * pf_lin_data[i_base + 1];
#endif
}

static float Lin2Db( float f_lin, filter_sys_t * p_sys )
{
    float f_scale = ( f_lin - LIN_MIN ) * DB_TABLE_SIZE / ( LIN_MAX - LIN_MIN );
    int i_base = Round( f_scale - 0.5f );
    float f_ofs = f_scale - i_base;
    float *pf_db_data = p_sys->pf_db_data;

    if( i_base < 2 )
    {
        return pf_db_data[2] * f_scale * 0.5f - 23.0f * ( 2.0f - f_scale );
    }
    else if( i_base > DB_TABLE_SIZE - 3 )
    {
        return pf_db_data[DB_TABLE_SIZE - 2];
    }

#ifdef DB_DEFAULT_CUBE
    return CubeInterp( f_ofs, pf_db_data[i_base - 1],
                              pf_db_data[i_base],
                              pf_db_data[i_base + 1],
                              pf_db_data[i_base + 2] );
#else
    return ( 1.0f - f_ofs ) * pf_db_data[i_base]
                  + f_ofs   * pf_db_data[i_base + 1];
#endif
}

#ifdef DB_DEFAULT_CUBE
/* Cubic interpolation function */
static float CubeInterp( const float f_fr, const float f_inm1,
                                           const float f_in,
                                           const float f_inp1,
                                           const float f_inp2 )
{
    return f_in + 0.5f * f_fr * ( f_inp1 - f_inm1 +
         f_fr * ( 4.0f * f_inp1 + 2.0f * f_inm1 - 5.0f * f_in - f_inp2 +
         f_fr * ( 3.0f * ( f_in - f_inp1 ) - f_inm1 + f_inp2 ) ) );
}
#endif

/* Zero out denormals by adding and subtracting a small number, from Laurent
 * de Soras */
static void RoundToZero( float *pf_x )
{
    static const float f_anti_denormal = 1e-18;

    *pf_x += f_anti_denormal;
    *pf_x -= f_anti_denormal;
}

/* A set of branchless clipping operations from Laurent de Soras */

static float Max( float f_x, float f_a )
{
    f_x -= f_a;
    f_x += fabsf( f_x );
    f_x *= 0.5f;
    f_x += f_a;

    return f_x;
}

static float Clamp( float f_x, float f_a, float f_b )
{
    const float f_x1 = fabsf( f_x - f_a );
    const float f_x2 = fabsf( f_x - f_b );

    f_x = f_x1 + f_a + f_b;
    f_x -= f_x2;
    f_x *= 0.5f;

    return f_x;
}

/* Round float to int using IEEE int* hack */
static int Round( float f_x )
{
    ls_pcast32 p;

    p.f = f_x;
    p.f += ( 3 << 22 );

    return p.i - 0x4b400000;
}

/* Calculate current level from root-mean-squared of circular buffer ("RMS") */
static float RmsEnvProcess( rms_env * p_r, const float f_x )
{
    /* Remove the old term from the sum */
    p_r->f_sum -= p_r->pf_buf[p_r->i_pos];

    /* Add the new term to the sum */
    p_r->f_sum += f_x;

    /* If the sum is small enough, make it zero */
    if( p_r->f_sum < 1.0e-6f )
    {
        p_r->f_sum = 0.0f;
    }

    /* Replace the old term in the array with the new one */
    p_r->pf_buf[p_r->i_pos] = f_x;

    /* Go to the next position for the next RMS calculation */
    p_r->i_pos = ( p_r->i_pos + 1 ) % ( p_r->i_count );

    /* Return the RMS value */
    return sqrt( p_r->f_sum / p_r->i_count );
}

/* Output the compressed delayed buffer and store the current buffer.  Uses a
 * circular array, just like the one used in calculating the RMS of the buffer
 */
static void BufferProcess( float * pf_buf, int i_channels, float f_gain,
                           float f_mug, lookahead * p_la )
{
    /* Loop through every channel */
    for( int i_chan = 0; i_chan < i_channels; i_chan++ )
    {
        float f_x = pf_buf[i_chan]; /* Current buffer value */

        /* Output the compressed delayed buffer value */
        pf_buf[i_chan] = p_la->p_buf[p_la->i_pos].pf_vals[i_chan]
                       * f_gain * f_mug;

        /* Update the delayed buffer value */
        p_la->p_buf[p_la->i_pos].pf_vals[i_chan] = f_x;
    }

    /* Go to the next delayed buffer value for the next run */
    p_la->i_pos = ( p_la->i_pos + 1 ) % ( p_la->i_count );
}

/*****************************************************************************
 * Callback functions
 *****************************************************************************/
static int RMSPeakCallback( vlc_object_t *p_this, char const *psz_cmd,
                            vlc_value_t oldval, vlc_value_t newval,
                            void * p_data )
{
    VLC_UNUSED(p_this); VLC_UNUSED(psz_cmd); VLC_UNUSED(oldval);
    filter_sys_t *p_sys = p_data;

    vlc_mutex_lock( &p_sys->lock );
    p_sys->f_rms_peak = Clamp( newval.f_float, 0.0f, 1.0f );
    vlc_mutex_unlock( &p_sys->lock );

    return VLC_SUCCESS;
}

static int AttackCallback( vlc_object_t *p_this, char const *psz_cmd,
                           vlc_value_t oldval, vlc_value_t newval,
                           void * p_data )
{
    VLC_UNUSED(p_this); VLC_UNUSED(psz_cmd); VLC_UNUSED(oldval);
    filter_sys_t *p_sys = p_data;

    vlc_mutex_lock( &p_sys->lock );
    p_sys->f_attack = Clamp( newval.f_float, 1.5f, 400.0f );
    vlc_mutex_unlock( &p_sys->lock );

    return VLC_SUCCESS;
}

static int ReleaseCallback( vlc_object_t *p_this, char const *psz_cmd,
                            vlc_value_t oldval, vlc_value_t newval,
                            void * p_data )
{
    VLC_UNUSED(p_this); VLC_UNUSED(psz_cmd); VLC_UNUSED(oldval);
    filter_sys_t *p_sys = p_data;

    vlc_mutex_lock( &p_sys->lock );
    p_sys->f_release = Clamp( newval.f_float, 2.0f, 800.0f );
    vlc_mutex_unlock( &p_sys->lock );

    return VLC_SUCCESS;
}

static int ThresholdCallback( vlc_object_t *p_this, char const *psz_cmd,
                              vlc_value_t oldval, vlc_value_t newval,
                              void * p_data )
{
    VLC_UNUSED(p_this); VLC_UNUSED(psz_cmd); VLC_UNUSED(oldval);
    filter_sys_t *p_sys = p_data;

    vlc_mutex_lock( &p_sys->lock );
    p_sys->f_threshold = Clamp( newval.f_float, -30.0f, 0.0f );
    vlc_mutex_unlock( &p_sys->lock );

    return VLC_SUCCESS;
}

static int RatioCallback( vlc_object_t *p_this, char const *psz_cmd,
                          vlc_value_t oldval, vlc_value_t newval,
                          void * p_data )
{
    VLC_UNUSED(p_this); VLC_UNUSED(psz_cmd); VLC_UNUSED(oldval);
    filter_sys_t *p_sys = p_data;

    vlc_mutex_lock( &p_sys->lock );
    p_sys->f_ratio = Clamp( newval.f_float, 1.0f, 20.0f );
    vlc_mutex_unlock( &p_sys->lock );

    return VLC_SUCCESS;
}

static int KneeCallback( vlc_object_t *p_this, char const *psz_cmd,
                         vlc_value_t oldval, vlc_value_t newval,
                         void * p_data )
{
    VLC_UNUSED(p_this); VLC_UNUSED(psz_cmd); VLC_UNUSED(oldval);
    filter_sys_t *p_sys = p_data;

    vlc_mutex_lock( &p_sys->lock );
    p_sys->f_knee = Clamp( newval.f_float, 1.0f, 10.0f );
    vlc_mutex_unlock( &p_sys->lock );

    return VLC_SUCCESS;
}

static int MakeupGainCallback( vlc_object_t *p_this, char const *psz_cmd,
                               vlc_value_t oldval, vlc_value_t newval,
                               void * p_data )
{
    VLC_UNUSED(p_this); VLC_UNUSED(psz_cmd); VLC_UNUSED(oldval);
    filter_sys_t *p_sys = p_data;

    vlc_mutex_lock( &p_sys->lock );
    p_sys->f_makeup_gain = Clamp( newval.f_float, 0.0f, 24.0f );
    vlc_mutex_unlock( &p_sys->lock );

    return VLC_SUCCESS;
}