--- /dev/null
+/*****************************************************************************
+ * gain.c : gain control filter
+ *****************************************************************************
+ * Copyright © 2012 VLC authors and VideoLAN
+ *
+ * Authors: Ludovic Fauvet <etix@videolan.org>
+ *
+ * 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 <vlc_common.h>
+#include <vlc_aout.h>
+#include <vlc_aout_mixer.h>
+#include <vlc_filter.h>
+#include <vlc_plugin.h>
+
+
+/*****************************************************************************
+ * Local prototypes
+ *****************************************************************************/
+
+static int Open ( vlc_object_t * );
+static void Close ( vlc_object_t * );
+static block_t *Process ( filter_t *, block_t * );
+
+struct filter_sys_t
+{
+ float f_gain;
+ audio_mixer_t* p_mixer;
+};
+
+
+/*****************************************************************************
+ * Module descriptor
+ *****************************************************************************/
+
+#define GAIN_VALUE_TEXT N_( "Gain multiplier" )
+#define GAIN_VALUE_LONGTEXT N_( "Increase or decrease the gain (default 1.0)" )
+
+vlc_module_begin()
+ set_shortname( N_("Gain") )
+ set_description( N_("Gain control filter") )
+ set_category( CAT_AUDIO )
+ set_subcategory( SUBCAT_AUDIO_AFILTER )
+
+ add_float( "gain-value", 1.0, GAIN_VALUE_TEXT,
+ GAIN_VALUE_LONGTEXT, false )
+
+ set_capability( "audio filter", 0 )
+ set_callbacks( Open, Close )
+vlc_module_end()
+
+
+/*****************************************************************************
+ * Open: initialize filter
+ *****************************************************************************/
+
+static int Open( vlc_object_t *p_this )
+{
+ filter_t *p_filter = (filter_t *)p_this;
+ filter_sys_t *p_sys;
+
+ if ( !AOUT_FMTS_IDENTICAL( &p_filter->fmt_in.audio, &p_filter->fmt_out.audio ) )
+ {
+ msg_Warn( p_filter, "bad input or output format" );
+ return VLC_EGENERIC;
+ }
+
+ p_sys = p_filter->p_sys = malloc( sizeof( *p_sys ) );
+ if( !p_sys )
+ return VLC_ENOMEM;
+
+ p_sys->p_mixer = aout_MixerNew( p_this, p_filter->fmt_in.audio.i_format );
+ if( !p_sys->p_mixer )
+ {
+ msg_Warn( p_filter, "unsupported format" );
+ free( p_sys );
+ return VLC_EGENERIC;
+ }
+
+ p_sys->f_gain = var_InheritFloat( p_filter->p_parent, "gain-value" );
+ msg_Dbg( p_filter, "gain multiplier sets to %.2fx", p_sys->f_gain );
+
+ p_filter->pf_audio_filter = Process;
+ return VLC_SUCCESS;
+}
+
+
+/*****************************************************************************
+ * Process: process samples buffer
+ *****************************************************************************/
+
+static block_t *Process( filter_t *p_filter, block_t *p_block )
+{
+ filter_sys_t *p_sys = p_filter->p_sys;
+
+ aout_MixerRun( p_sys->p_mixer, p_block, p_sys->f_gain );
+
+ return p_block;
+}
+
+
+/*****************************************************************************
+ * Close: close filter
+ *****************************************************************************/
+
+static void Close( vlc_object_t *p_this )
+{
+ filter_t *p_filter = (filter_t*)p_this;
+ filter_sys_t *p_sys = p_filter->p_sys;
+
+ aout_MixerDelete( p_sys->p_mixer );
+ free( p_sys );
+}