--- /dev/null
+/*****************************************************************************
+ * stereo_widen.c : simple stereo widening effect
+ *****************************************************************************
+ * Copyright (C) 2012 VLC authors and VideoLAN
+ *
+ * Author : Sukrit Sangwan < sukritsangwan at gmail dot com >
+ *
+ * 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.
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <vlc_common.h>
+#include <vlc_aout.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 *Filter ( filter_t *, block_t * );
+static int paramCallback( vlc_object_t *, char const *, vlc_value_t ,
+ vlc_value_t , void * );
+
+struct filter_sys_t
+{
+ float *pf_begin; /* circular buffer to store samples */
+ float *pf_write; /* where to write current sample */
+ int i_len; /* delay in number of samples */
+ float f_delay; /* delay in milliseconds */
+ float f_feedback;
+ float f_crossfeed;
+ float f_dry_mix;
+ bool b_free_buf; /* used if callback to delay fails to *
+ * allocate buffer, then dont free it twice */
+};
+
+#define DESCRIPTION N_("This filter enhances stereo effect by \
+ suppressing mono,i.e. signal common to both channels, \
+ and by delaying the signal of left into right and vice versa \
+ thereby widening stereo effect")
+#define DELAY_TEXT N_("Delay time")
+#define DELAY_LONGTEXT N_("Time in ms of the delay of left signal into right \
+ and vice versa.")
+#define FEEDBACK_TEXT N_("Feedback Gain")
+#define FEEDBACK_LONGTEXT N_("Amount of gain in delayed left signal into \
+ right and vice versa. Gives a delay effect of left signal in \
+ right output and vice versa which gives widening effect")
+#define CROSSFEED_TEXT N_("Crossfeed")
+#define CROSSFEED_LONGTEXT N_("Cross feed of left into right with inverted \
+ phase. This helps in suppression of mono. If its value is 1 it \
+ cancels all the signal common to both channels")
+#define DRYMIX_TEXT N_("Dry Mix")
+#define DRYMIX_LONGTEXT N_("Level of input signal of original channel")
+
+/*****************************************************************************
+ * Module descriptor
+ *****************************************************************************/
+vlc_module_begin ()
+ set_shortname( N_("stereo_widen") )
+ set_description( DESCRIPTION )
+ set_category( CAT_AUDIO )
+ set_subcategory( SUBCAT_AUDIO_AFILTER )
+ set_capability( "audio filter", 0 )
+ set_callbacks( Open, Close )
+
+ add_float( "delay", 20, DELAY_TEXT, DELAY_LONGTEXT, true )
+ add_float_with_range( "feedback", 0.3, 0.0, 0.9,
+ FEEDBACK_TEXT, FEEDBACK_LONGTEXT, true )
+ add_float_with_range( "crossfeed", 0.3, 0.0, 0.8,
+ CROSSFEED_TEXT, CROSSFEED_LONGTEXT, true )
+ add_float_with_range( "dry-mix", 0.8, 0.0, 1.0,
+ DRYMIX_TEXT, DRYMIX_LONGTEXT, true )
+vlc_module_end ()
+
+/*****************************************************************************
+ * Open: Allocate buffer
+ *****************************************************************************/
+static int Open( vlc_object_t *obj )
+{
+ filter_t *p_filter = (filter_t *)obj;
+ filter_sys_t *p_sys;
+
+ if( p_filter->fmt_in.audio.i_format != VLC_CODEC_FL32 ||
+ !AOUT_FMTS_IDENTICAL( &p_filter->fmt_in.audio, &p_filter->fmt_out.audio) )
+ return VLC_EGENERIC;
+
+ if( p_filter->fmt_in.audio.i_channels != 2 )
+ {
+ msg_Err ( p_filter, "stereo enhance requires stereo" );
+ return VLC_EGENERIC;
+ }
+
+ p_sys = p_filter->p_sys = malloc( sizeof(filter_sys_t) );
+ if( unlikely(!p_sys) )
+ return VLC_ENOMEM;
+
+#define CREATE_VAR( stor, var ) \
+ p_sys->stor = var_CreateGetFloat( obj, var ); \
+ var_AddCallback( p_filter, var, paramCallback, p_sys );
+
+ CREATE_VAR( f_delay, "delay" )
+ CREATE_VAR( f_feedback, "feedback" )
+ CREATE_VAR( f_crossfeed, "crossfeed" )
+ CREATE_VAR( f_dry_mix, "dry-mix" )
+
+ /* Compute buffer length and allocate space */
+ p_sys->i_len = 2 * p_sys->f_delay * p_filter->fmt_in.audio.i_rate / 1000;
+ p_sys->pf_begin = calloc( p_sys->i_len + 2, sizeof(float) );
+ if( unlikely(!p_sys->pf_begin) )
+ {
+ free( p_sys );
+ return VLC_ENOMEM;
+ }
+ p_sys->b_free_buf = true;
+ p_sys->pf_write = p_sys->pf_begin;
+ p_filter->pf_audio_filter = Filter;
+ return VLC_SUCCESS;
+}
+
+
+/*****************************************************************************
+ * Filter: process each sample
+ *****************************************************************************/
+static block_t *Filter( filter_t *p_filter, block_t *p_block )
+{
+ filter_sys_t *p_sys = p_filter->p_sys;
+ float *p_out = (float *)p_block->p_buffer;
+ float *pf_read;
+
+ for (unsigned i = p_block->i_nb_samples; i > 0; i--)
+ {
+ pf_read = p_sys->pf_write + 2;
+ /* if at end of buffer put read ptr at begin */
+ if( pf_read > p_sys->pf_begin + p_sys->i_len )
+ pf_read = p_sys->pf_begin;
+
+ float left = p_out[0];
+ float right = p_out[1];
+
+ *(p_out++) = p_sys->f_dry_mix * left - p_sys->f_crossfeed * right
+ - p_sys->f_feedback * pf_read[1];
+ *(p_out++) = p_sys->f_dry_mix * right - p_sys->f_crossfeed * left
+ - p_sys->f_feedback * pf_read[0];
+ p_sys->pf_write[0] = left ;
+ p_sys->pf_write[1] = right;
+
+ /* if at end of buffer place pf_write at begin */
+ if( p_sys->pf_write == p_sys->pf_begin + p_sys->i_len )
+ p_sys->pf_write = p_sys->pf_begin;
+ else
+ p_sys->pf_write += 2;
+ }
+
+ return p_block;
+}
+
+/*****************************************************************************
+ * Close: close the plugin
+ *****************************************************************************/
+static void Close( vlc_object_t *obj )
+{
+ filter_t *p_filter = (filter_t *)obj;
+ filter_sys_t *p_sys = p_filter->p_sys;
+
+#define DEL_VAR(var) \
+ var_DelCallback( p_filter, var, paramCallback, p_sys ); \
+ var_Destroy( p_filter, var );
+
+ DEL_VAR( "feedback" );
+ DEL_VAR( "crossfeed" );
+ DEL_VAR( "dry-mix" );
+ var_Destroy( p_filter, "delay" );
+ if( p_sys->b_free_buf )
+ free( p_sys->pf_begin );
+ free( p_sys );
+}
+
+
+/**********************************************************************
+ * Callback to update params on the fly
+ **********************************************************************/
+static int paramCallback( vlc_object_t *p_this, char const *psz_var,
+ vlc_value_t oldval, vlc_value_t newval,
+ void *p_data )
+{
+ filter_t *p_filter = (filter_t *)p_this;
+ filter_sys_t *p_sys = (filter_sys_t *) p_data;
+
+ VLC_UNUSED(oldval);
+ VLC_UNUSED(p_this);
+
+ if( !strcmp( psz_var, "delay" ) )
+ {
+ p_sys->f_delay = newval.f_float;
+ /* Free previous buffer and allocate new circular buffer */
+ free( p_sys->pf_begin );
+ p_sys->i_len = 2 * p_sys->f_delay * p_filter->fmt_in.audio.i_rate /1000;
+ p_sys->pf_begin = calloc( p_sys->i_len + 2, sizeof(float) );
+ if( unlikely(!p_sys->pf_begin) )
+ {
+ p_sys->b_free_buf = false;
+ msg_Dbg( p_filter, "Couldnt allocate buffer for delay" );
+ Close( p_this );
+ }
+ }
+ else if( !strcmp( psz_var, "feedback" ) )
+ p_sys->f_feedback = newval.f_float;
+ else if( !strcmp( psz_var, "crossfeed" ) )
+ p_sys->f_feedback = newval.f_float;
+ else if( !strcmp( psz_var, "dry-mix" ) )
+ p_sys->f_dry_mix = newval.f_float;
+
+ return VLC_SUCCESS;
+}
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