headphone.c

video linux conference

/*****************************************************************************
 * headphone.c : headphone virtual spatialization channel mixer module
 *               -> gives the feeling of a real room with a simple headphone
 *****************************************************************************
 * Copyright (C) 2002 VideoLAN
 * $Id: headphone.c 10112 2005-03-03 06:58:04Z zorglub $
 *
 * Authors: Boris Dor鑣 <[e-mail]>
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/
#include <stdlib.h>                                      /* malloc(), free() */
#include <string.h>
#include <math.h>                                        /* sqrt */

#include <vlc/vlc.h>
#include "audio_output.h"
#include "aout_internal.h"

/*****************************************************************************
 * Local prototypes
 *****************************************************************************/
static int  Create    ( vlc_object_t * );
static void Destroy   ( vlc_object_t * );

static void DoWork    ( aout_instance_t *, aout_filter_t *, aout_buffer_t *,
                        aout_buffer_t * );

/*****************************************************************************
 * Module descriptor
 *****************************************************************************/
#define MODULE_DESCRIPTION N_ ( \
     "This effect gives you the feeling that you are standing in a room " \
     "with a complete 5.1 speaker set when using only a headphone, " \
     "providing a more realistic sound experience. It should also be " \
     "more comfortable and less tiring when listening to music for " \
     "long periods of time.\nIt works with any source format from mono " \
     "to 5.1.")

#define HEADPHONE_DIM_TEXT N_("Characteristic dimension")
#define HEADPHONE_DIM_LONGTEXT N_( \
     "Distance between front left speaker and listener in meters.")

vlc_module_begin();
    set_description( N_("Headphone channel mixer with virtual spatialization effect") );
    set_shortname( _("Headphone effect") );
    set_category( CAT_AUDIO );
    set_subcategory( SUBCAT_AUDIO_AFILTER );

    add_integer( "headphone-dim", 10, NULL, HEADPHONE_DIM_TEXT,
                 HEADPHONE_DIM_LONGTEXT, VLC_FALSE );

    set_capability( "audio filter", 0 );
    set_callbacks( Create, Destroy );
    add_shortcut( "headphone" );
vlc_module_end();


/*****************************************************************************
 * Internal data 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 aout_filter_sys_t
{
    size_t i_overflow_buffer_size;/* in bytes */
    byte_t * p_overflow_buffer;
    unsigned int i_nb_atomic_operations;
    struct atomic_operation_t * p_atomic_operations;
};

/*****************************************************************************
 * 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 aout_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_channel_amplitude_factor )
{
    double d_c = 340; /*sound celerity (unit: m/s)*/

    /* 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 );
    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 );
    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 ( aout_filter_t * p_filter , struct aout_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_filter , "headphone-dim" );
    double d_z = d_x;
    double d_z_rear = -d_x/3;
    unsigned int i_next_atomic_operation;
    int i_source_channel_offset;
    unsigned int i;

    if ( p_data == NULL )
    {
        msg_Dbg ( p_filter, "passing a null pointer as argument" );
        return 0;
    }

    /* Number of elementary operations */
    p_data->i_nb_atomic_operations = i_nb_channels * 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 )
    {
        msg_Err( p_filter, "out of memory" );
        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 , 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 , 2.0 / 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 , 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 , 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 , 1.5 / i_nb_channels );
        i_next_atomic_operation += 2;
        i_source_channel_offset++;