modules/audio_filter/gain.c

   1 /*****************************************************************************
   2  * gain.c : gain control filter
   3  *****************************************************************************
   4  * Copyright © 2012 VLC authors and VideoLAN
   5  *
   6  * Authors: Ludovic Fauvet <etix@videolan.org>
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU Lesser General Public License as published by
  10  * the Free Software Foundation; either version 2.1 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public License
  19  * along with this program; if not, write to the Free Software Foundation,
  20  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  21  *****************************************************************************/
  22
  23 /*****************************************************************************
  24  * Preamble
  25  *****************************************************************************/
  26
  27 #ifdef HAVE_CONFIG_H
  28 # include "config.h"
  29 #endif
  30
  31 #include <vlc_common.h>
  32 #include <vlc_aout.h>
  33 #include <vlc_aout_volume.h>
  34 #include <vlc_filter.h>
  35 #include <vlc_modules.h>
  36 #include <vlc_plugin.h>
  37
  38
  39 /*****************************************************************************
  40  * Local prototypes
  41  *****************************************************************************/
  42
  43 static int      Open        ( vlc_object_t * );
  44 static void     Close       ( vlc_object_t * );
  45 static block_t  *Process    ( filter_t *, block_t * );
  46
  47 struct filter_sys_t
  48 {
  49     audio_volume_t volume;
  50     float f_gain;
  51     module_t *module;
  52 };
  53
  54 /*****************************************************************************
  55  * Module descriptor
  56  *****************************************************************************/
  57
  58 #define GAIN_VALUE_TEXT N_( "Gain multiplier" )
  59 #define GAIN_VALUE_LONGTEXT N_( "Increase or decrease the gain (default 1.0)" )
  60
  61 vlc_module_begin()
  62     set_shortname( N_("Gain") )
  63     set_description( N_("Gain control filter") )
  64     set_category( CAT_AUDIO )
  65     set_subcategory( SUBCAT_AUDIO_AFILTER )
  66
  67     add_float( "gain-value", 1.0, GAIN_VALUE_TEXT,
  68                GAIN_VALUE_LONGTEXT, false )
  69
  70     set_capability( "audio filter", 0 )
  71     set_callbacks( Open, Close )
  72 vlc_module_end()
  73
  74
  75 /*****************************************************************************
  76  * Open: initialize filter
  77  *****************************************************************************/
  78
  79 static int Open( vlc_object_t *p_this )
  80 {
  81     filter_t *p_filter = (filter_t *)p_this;
  82     filter_sys_t *p_sys = vlc_object_create( p_this, sizeof( *p_sys ) );
  83     if( unlikely( p_sys == NULL ) )
  84         return VLC_ENOMEM;
  85
  86     p_filter->p_sys = p_sys;
  87     p_sys->volume.format = p_filter->fmt_in.audio.i_format;
  88     p_sys->module = module_need( &p_sys->volume, "audio volume", NULL, false );
  89     if( p_sys->module == NULL )
  90     {
  91         msg_Warn( p_filter, "unsupported format" );
  92         vlc_object_release( &p_sys->volume );
  93         return VLC_EGENERIC;
  94     }
  95
  96     p_sys->f_gain = var_InheritFloat( p_filter->obj.parent, "gain-value" );
  97     msg_Dbg( p_filter, "gain multiplier sets to %.2fx", p_sys->f_gain );
  98
  99     p_filter->fmt_out.audio = p_filter->fmt_in.audio;
 100     p_filter->pf_audio_filter = Process;
 101     return VLC_SUCCESS;
 102 }
 103
 104
 105 /*****************************************************************************
 106  * Process: process samples buffer
 107  *****************************************************************************/
 108
 109 static block_t *Process( filter_t *p_filter, block_t *p_block )
 110 {
 111     filter_sys_t *p_sys = p_filter->p_sys;
 112
 113     p_sys->volume.amplify( &p_sys->volume, p_block, p_sys->f_gain );
 114     return p_block;
 115 }
 116
 117
 118 /*****************************************************************************
 119  * Close: close filter
 120  *****************************************************************************/
 121
 122 static void Close( vlc_object_t *p_this )
 123 {
 124     filter_t *p_filter = (filter_t*)p_this;
 125     filter_sys_t *p_sys = p_filter->p_sys;
 126
 127     module_unneed( &p_sys->volume, p_sys->module );
 128     vlc_object_release( &p_sys->volume );
 129 }