mono.c

VLC Player Source Code

/*****************************************************************************
 * mono.c : stereo2mono downmixsimple channel mixer plug-in
 *****************************************************************************
 * Copyright (C) 2006 M2X
 * $Id$
 *
 * Authors: Jean-Paul Saman <jpsaman at m2x dot nl>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU 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>                                        /* sqrt */

#ifdef HAVE_STDINT_H
#   include <stdint.h>                                         /* int16_t .. */
#elif defined(HAVE_INTTYPES_H)
#   include <inttypes.h>                                       /* int16_t .. */
#endif

#ifdef HAVE_UNISTD_H
#   include <unistd.h>
#endif

#include <vlc_common.h>
#include <vlc_plugin.h>
#include <vlc_es.h>
#include <vlc_block.h>
#include <vlc_filter.h>
#include <vlc_aout.h>

/*****************************************************************************
 * Local prototypes
 *****************************************************************************/
static int  OpenFilter    ( vlc_object_t * );
static void CloseFilter   ( vlc_object_t * );

static block_t *Convert( filter_t *p_filter, block_t *p_block );

static unsigned int stereo_to_mono( aout_filter_t *, aout_buffer_t *,
                                    aout_buffer_t * );
static unsigned int mono( aout_filter_t *, aout_buffer_t *, aout_buffer_t * );
static void stereo2mono_downmix( aout_filter_t *, aout_buffer_t *,
                                 aout_buffer_t * );

/*****************************************************************************
 * Local structures
 *****************************************************************************/
struct atomic_operation_t
{
    int i_source_channel_offset;
    int i_dest_channel_offset;
    unsigned int i_delay;/* in sample unit */
    double d_amplitude_factor;
};

struct filter_sys_t
{
    bool b_downmix;

    unsigned int i_nb_channels; /* number of int16_t per sample */
    int i_channel_selected;
    int i_bitspersample;

    size_t i_overflow_buffer_size;/* in bytes */
    uint8_t * p_overflow_buffer;
    unsigned int i_nb_atomic_operations;
    struct atomic_operation_t * p_atomic_operations;
};

#define MONO_DOWNMIX_TEXT N_("Use downmix algorithm")
#define MONO_DOWNMIX_LONGTEXT N_("This option selects a stereo to mono " \
    "downmix algorithm that is used in the headphone channel mixer. It " \
    "gives the effect of standing in a room full of speakers." )

#define MONO_CHANNEL_TEXT N_("Select channel to keep")
#define MONO_CHANNEL_LONGTEXT N_("This option silences all other channels " \
    "except the selected channel. Choose one from (0=left, 1=right, " \
    "2=rear left, 3=rear right, 4=center, 5=left front)")

static const int pi_pos_values[] = { 0, 1, 2, 4, 8, 5 };
static const char *const ppsz_pos_descriptions[] =
{ N_("Left"), N_("Right"), N_("Left rear"), N_("Right rear"), N_("Center"),
  N_("Left front") };

/* our internal channel order (WG-4 order) */
static const uint32_t pi_channels_out[] =
{ AOUT_CHAN_LEFT, AOUT_CHAN_RIGHT, AOUT_CHAN_REARLEFT, AOUT_CHAN_REARRIGHT,
  AOUT_CHAN_CENTER, AOUT_CHAN_LFE, 0 };

#define MONO_CFG "sout-mono-"
/*****************************************************************************
 * Module descriptor
 *****************************************************************************/
vlc_module_begin();
    set_description( N_("Audio filter for stereo to mono conversion") );
    set_capability( "audio filter2", 2 );

    add_bool( MONO_CFG "downmix", true, NULL, MONO_DOWNMIX_TEXT,
              MONO_DOWNMIX_LONGTEXT, false );
    add_integer( MONO_CFG "channel", -1, NULL, MONO_CHANNEL_TEXT,
        MONO_CHANNEL_LONGTEXT, false );
        change_integer_list( pi_pos_values, ppsz_pos_descriptions, NULL );

    set_category( CAT_AUDIO );
    set_subcategory( SUBCAT_AUDIO_MISC );
    set_callbacks( OpenFilter, CloseFilter );
    set_shortname( "Mono" );
vlc_module_end();

/* Init() and ComputeChannelOperations() -
 * Code taken from modules/audio_filter/channel_mixer/headphone.c
 * converted from float into int16_t based downmix
 * Written by Boris Dorès <[e-mail]>
 */

/*****************************************************************************
 * Init: initialize internal data structures
 * and computes the needed atomic operations
 *****************************************************************************/
/* x and z represent the coordinates of the virtual speaker
 *  relatively to the center of the listener's head, measured in meters :
 *
 *  left              right
 *Z
 *-
 *a          head
 *x
 *i
 *s
 *  rear left    rear right
 *
 *          x-axis
 *  */
static void ComputeChannelOperations( struct filter_sys_t * p_data,
        unsigned int i_rate, unsigned int i_next_atomic_operation,
        int i_source_channel_offset, double d_x, double d_z,
        double d_compensation_length, double d_channel_amplitude_factor )
{
    double d_c = 340; /*sound celerity (unit: m/s)*/
    double d_compensation_delay = (d_compensation_length-0.1) / d_c * i_rate;

    /* Left ear */
    p_data->p_atomic_operations[i_next_atomic_operation]
        .i_source_channel_offset = i_source_channel_offset;
    p_data->p_atomic_operations[i_next_atomic_operation]
        .i_dest_channel_offset = 0;/* left */
    p_data->p_atomic_operations[i_next_atomic_operation]
        .i_delay = (int)( sqrt( (-0.1-d_x)*(-0.1-d_x) + (0-d_z)*(0-d_z) )
                          / d_c * i_rate - d_compensation_delay );
    if( d_x < 0 )
    {
        p_data->p_atomic_operations[i_next_atomic_operation]
            .d_amplitude_factor = d_channel_amplitude_factor * 1.1 / 2;
    }
    else if( d_x > 0 )
    {
        p_data->p_atomic_operations[i_next_atomic_operation]
            .d_amplitude_factor = d_channel_amplitude_factor * 0.9 / 2;
    }
    else
    {
        p_data->p_atomic_operations[i_next_atomic_operation]
            .d_amplitude_factor = d_channel_amplitude_factor / 2;
    }

    /* Right ear */
    p_data->p_atomic_operations[i_next_atomic_operation + 1]
        .i_source_channel_offset = i_source_channel_offset;
    p_data->p_atomic_operations[i_next_atomic_operation + 1]
        .i_dest_channel_offset = 1;/* right */
    p_data->p_atomic_operations[i_next_atomic_operation + 1]
        .i_delay = (int)( sqrt( (0.1-d_x)*(0.1-d_x) + (0-d_z)*(0-d_z) )
                          / d_c * i_rate - d_compensation_delay );
    if( d_x < 0 )
    {
        p_data->p_atomic_operations[i_next_atomic_operation + 1]
            .d_amplitude_factor = d_channel_amplitude_factor * 0.9 / 2;
    }
    else if( d_x > 0 )
    {
        p_data->p_atomic_operations[i_next_atomic_operation + 1]
            .d_amplitude_factor = d_channel_amplitude_factor * 1.1 / 2;
    }
    else
    {
        p_data->p_atomic_operations[i_next_atomic_operation + 1]
            .d_amplitude_factor = d_channel_amplitude_factor / 2;
    }
}

static int Init( vlc_object_t *p_this, struct filter_sys_t * p_data,
                 unsigned int i_nb_channels, uint32_t i_physical_channels,
                 unsigned int i_rate )
{
    double d_x = config_GetInt( p_this, "headphone-dim" );
    double d_z = d_x;
    double d_z_rear = -d_x/3;
    double d_min = 0;
    unsigned int i_next_atomic_operation;
    int i_source_channel_offset;
    unsigned int i;

    if( config_GetInt( p_this, "headphone-compensate" ) )
    {
        /* minimal distance to any speaker */
        if( i_physical_channels & AOUT_CHAN_REARCENTER )
        {
            d_min = d_z_rear;
        }
        else
        {
            d_min = d_z;
        }
    }

    /* Number of elementary operations */
    p_data->i_nb_atomic_operations = i_nb_channels * 2;
    if( i_physical_channels & AOUT_CHAN_CENTER )
    {
        p_data->i_nb_atomic_operations += 2;
    }
    p_data->p_atomic_operations = malloc( sizeof(struct atomic_operation_t)
            * p_data->i_nb_atomic_operations );
    if( p_data->p_atomic_operations == NULL )
        return -1;

    /* For each virtual speaker, computes elementary wave propagation time
     * to each ear */
    i_next_atomic_operation = 0;
    i_source_channel_offset = 0;
    if( i_physical_channels & AOUT_CHAN_LEFT )
    {
        ComputeChannelOperations( p_data , i_rate
                , i_next_atomic_operation , i_source_channel_offset
                , -d_x , d_z , d_min , 2.0 / i_nb_channels );
        i_next_atomic_operation += 2;
        i_source_channel_offset++;
    }
    if( i_physical_channels & AOUT_CHAN_RIGHT )
    {
        ComputeChannelOperations( p_data , i_rate
                , i_next_atomic_operation , i_source_channel_offset
                , d_x , d_z , d_min , 2.0 / i_nb_channels );
        i_next_atomic_operation += 2;
        i_source_channel_offset++;
    }
    if( i_physical_channels & AOUT_CHAN_MIDDLELEFT )
    {
        ComputeChannelOperations( p_data , i_rate
                , i_next_atomic_operation , i_source_channel_offset
                , -d_x , 0 , d_min , 1.5 / i_nb_channels );
        i_next_atomic_operation += 2;
        i_source_channel_offset++;
    }
    if( i_physical_channels & AOUT_CHAN_MIDDLERIGHT )
    {
        ComputeChannelOperations( p_data , i_rate
                , i_next_atomic_operation , i_source_channel_offset
                , d_x , 0 , d_min , 1.5 / i_nb_channels );
        i_next_atomic_operation += 2;
        i_source_channel_offset++;
    }
    if( i_physical_channels & AOUT_CHAN_REARLEFT )
    {
        ComputeChannelOperations( p_data , i_rate
                , i_next_atomic_operation , i_source_channel_offset
                , -d_x , d_z_rear , d_min , 1.5 / i_nb_channels );
        i_next_atomic_operation += 2;
        i_source_channel_offset++;
    }
    if( i_physical_channels & AOUT_CHAN_REARRIGHT )
    {
        ComputeChannelOperations( p_data , i_rate
                , i_next_atomic_operation , i_source_channel_offset
                , d_x , d_z_rear , d_min , 1.5 / i_nb_channels );
        i_next_atomic_operation += 2;
        i_source_channel_offset++;
    }
    if( i_physical_channels & AOUT_CHAN_REARCENTER )
    {
        ComputeChannelOperations( p_data , i_rate
                , i_next_atomic_operation , i_source_channel_offset
                , 0 , -d_z , d_min , 1.5 / i_nb_channels );
        i_next_atomic_operation += 2;
        i_source_channel_offset++;
    }
    if( i_physical_channels & AOUT_CHAN_CENTER )
    {
        /* having two center channels increases the spatialization effect */
        ComputeChannelOperations( p_data , i_rate
                , i_next_atomic_operation , i_source_channel_offset
                , d_x / 5.0 , d_z , d_min , 0.75 / i_nb_channels );
        i_next_atomic_operation += 2;
        ComputeChannelOperations( p_data , i_rate
                , i_next_atomic_operation , i_source_channel_offset
                , -d_x / 5.0 , d_z , d_min , 0.75 / i_nb_channels );
        i_next_atomic_operation += 2;
        i_source_channel_offset++;
    }
    if( i_physical_channels & AOUT_CHAN_LFE )
    {
        ComputeChannelOperations( p_data , i_rate
                , i_next_atomic_operation , i_source_channel_offset
                , 0 , d_z_rear , d_min , 5.0 / i_nb_channels );
        i_next_atomic_operation += 2;
        i_source_channel_offset++;
    }

    /* Initialize the overflow buffer
     * we need it because the process induce a delay in the samples */
    p_data->i_overflow_buffer_size = 0;
    for( i = 0 ; i < p_data->i_nb_atomic_operations ; i++ )
    {
        if( p_data->i_overflow_buffer_size
                < p_data->p_atomic_operations[i].i_delay * 2 * sizeof (int16_t) )
        {
            p_data->i_overflow_buffer_size
                = p_data->p_atomic_operations[i].i_delay * 2 * sizeof (int16_t);
        }
    }
    p_data->p_overflow_buffer = malloc( p_data->i_overflow_buffer_size );
    if( p_data->p_overflow_buffer == NULL )
    {
        free( p_data->p_atomic_operations );
        return -1;
    }
    memset( p_data->p_overflow_buffer, 0, p_data->i_overflow_buffer_size );

    /* end */
    return 0;