Added a very trivial volume normalizer

modules/audio_filter/Modules.am

 SOURCES_equalizer = equalizer.c
+SOURCES_normvol = normvol.c

modules/audio_filter/normvol.c

+/*****************************************************************************
+ * normvol.c :  volume normalizer
+ *****************************************************************************
+ * Copyright (C) 2001 VideoLAN
+ * $Id: equalizer.c,v 1.21 2003/07/31 23:44:49 zorglub Exp $
+ *
+ * Authors: Clment Stenac <zorglub@videolan.org>
+ *
+ * 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.
+ *****************************************************************************/
+
+/*
+ * TODO:
+ *
+ * We should detect fast power increases and react faster to these
+ * This way, we can increase the buffer size to get a more stable filter */
+
+
+/*****************************************************************************
+ * Preamble
+ *****************************************************************************/
+#include <stdlib.h>                                      /* malloc(), free() */
+#include <string.h>
+
+#include <errno.h>                                                 /* ENOMEM */
+#include <stdio.h>
+#include <ctype.h>
+#include <signal.h>
+
+#include <math.h>
+
+
+#include <vlc/vlc.h>
+#include <vlc/aout.h>
+
+#include <aout_internal.h>
+
+/*****************************************************************************
+ * Local prototypes
+ *****************************************************************************/
+
+static int  Open     ( vlc_object_t * );
+static void Close    ( vlc_object_t * );
+static void DoWork   ( aout_instance_t * , aout_filter_t *,
+                aout_buffer_t * , aout_buffer_t *);
+
+struct aout_filter_sys_t {
+    int i_nb;
+    float *p_last;
+    float f_max;
+};
+
+/*****************************************************************************
+ * Module descriptor
+ *****************************************************************************/
+#define BUFF_TEXT N_("Number of audio buffers" )
+#define BUFF_LONGTEXT N_("This is the number of audio buffers on which the " \
+                "power measurement is made. A higher number of buffers will " \
+                "increase the response time of the filter to a high " \
+                "power but will make it less sensitive to short variations " )
+
+#define LEVEL_TEXT N_("Max level" )
+#define LEVEL_LONGTEXT N_("If the average power over the last N buffers " \
+               "is higher than this value, the volume will be normalized." \
+               "This value is a positive floating point number. A value " \
+               "between 0.5 and 10 seems sensible." )
+
+vlc_module_begin();
+    set_description( _("Volume normalizer") );
+    add_shortcut("volnorm");
+    add_integer("norm-buff-size" , 20 , NULL , BUFF_TEXT, BUFF_LONGTEXT,
+                VLC_TRUE);
+    add_float("norm-max-level",2.0,NULL,"pouet","pouetpouet",VLC_TRUE);
+    set_capability( "audio filter", 0 );
+    set_callbacks( Open, Close );
+vlc_module_end();
+
+/*****************************************************************************
+ * Open: initialize and create stuff
+ *****************************************************************************/
+static int Open( vlc_object_t *p_this )
+{
+    aout_filter_t *p_filter = (aout_filter_t*)p_this;
+
+    struct aout_filter_sys_t *p_sys = p_filter->p_sys =
+            malloc( sizeof( struct aout_filter_sys_t ) );
+
+    if( p_filter->input.i_format != VLC_FOURCC('f','l','3','2' ) ||
+        p_filter->output.i_format != VLC_FOURCC('f','l','3','2') )
+    {
+            msg_Warn( p_filter, "Bad input or output format" );
+            return VLC_EGENERIC;
+    }
+
+    if ( !AOUT_FMTS_SIMILAR( &p_filter->input, &p_filter->output ) )
+    {
+        msg_Warn( p_filter, "input and output formats are not similar" );
+        return VLC_EGENERIC;
+    }
+
+    p_filter->pf_do_work = DoWork;
+    p_filter->b_in_place = VLC_TRUE;
+
+    int i_channels = aout_FormatNbChannels( &p_filter->input );
+
+    p_sys->i_nb =  var_CreateGetInteger( p_filter->p_parent, "norm-buff-size" );
+    p_sys->f_max = var_CreateGetFloat( p_filter->p_parent, "norm-max-level" );
+
+    if( p_sys->f_max <= 0 )
+    {
+        p_sys->f_max = 0.01;
+    }
+
+    /* We need to store (nb_buffers+1)*nb_channels floats */
+    p_sys->p_last = malloc( sizeof( float ) * (i_channels) *
+                            (p_filter->p_sys->i_nb + 2) );
+    memset( p_sys->p_last, 0 , sizeof( float ) * (i_channels) *
+                           (p_filter->p_sys->i_nb + 2) );
+    return VLC_SUCCESS;
+}
+
+/*****************************************************************************
+ * DoWork : normalizes and sends a buffer
+ *****************************************************************************/
+ static void DoWork( aout_instance_t *p_aout, aout_filter_t *p_filter,
+                     aout_buffer_t *p_in_buf, aout_buffer_t *p_out_buf )
+{
+    float *pf_sum;
+    float *pf_gain;
+    float f_average = 0;
+    int i, i_chan;
+
+    int i_samples = p_in_buf->i_nb_samples;
+    int i_channels = aout_FormatNbChannels( &p_filter->input );
+    float *p_out = (float*)p_out_buf->p_buffer;
+    float *p_in =  (float*)p_in_buf->p_buffer;
+
+    struct aout_filter_sys_t *p_sys = p_filter->p_sys;
+
+    pf_sum = (float *)malloc( sizeof(float) * i_channels );
+    memset( pf_sum, 0, sizeof(float) * i_channels );
+
+    pf_gain = (float *)malloc( sizeof(float) * i_channels );
+
+    p_out_buf->i_nb_samples = p_in_buf->i_nb_samples;
+    p_out_buf->i_nb_bytes = p_in_buf->i_nb_bytes;
+
+   /* Calculate the average power level on this buffer */
+   for( i = 0 ; i < i_samples; i++ )
+   {
+        for( i_chan = 0; i_chan < i_channels; i_chan++ )
+        {
+            float f_sample = p_in[i_chan];
+            float f_square = pow( f_sample, 2 );
+            pf_sum[i_chan] += f_square;
+        }
+        p_in += i_channels;
+   }
+
+   /* sum now contains for each channel the sigma(value) */
+   for( i_chan = 0; i_chan < i_channels; i_chan++ )
+   {
+        /* Shift our lastbuff */
+        memmove( &p_sys->p_last[ i_chan * p_sys->i_nb],
+                        &p_sys->p_last[i_chan * p_sys->i_nb + 1],
+                 (p_sys->i_nb-1) * sizeof( float ) );
+
+        /* Insert the new average : sqrt(sigma(value)) */
+        p_sys->p_last[ i_chan * p_sys->i_nb + p_sys->i_nb - 1] =
+                sqrt( pf_sum[i_chan] );
+
+        pf_sum[i_chan] = 0;
+
+        /* Get the average power on the lastbuff */
+        f_average = 0;
+        for( i = 0; i < p_sys->i_nb ; i++)
+        {
+            f_average += p_sys->p_last[ i_chan * p_sys->i_nb + i ];
+        }
+        f_average = f_average / p_sys->i_nb;
+
+        /* Seuil arbitraire */
+        p_sys->f_max = var_GetFloat( p_aout, "norm-max-level" );
+
+//        fprintf(stderr,"Average %f, max %f\n", f_average, p_sys->f_max );
+        if( f_average > p_sys->f_max )
+        {
+             pf_gain[i_chan] = f_average / p_sys->f_max;
+        }
+        else
+        {
+           pf_gain[i_chan] = 1;
+        }
+    }
+
+    /* Apply gain */
+    for( i = 0 ; i < i_samples ; i++)
+    {
+        for( i_chan = 0; i_chan < i_channels; i_chan++ )
+        {
+            p_out[i_chan] /= pf_gain[i_chan];
+        }
+        p_out += i_channels;
+    }
+
+    free( pf_sum );
+    free( pf_gain );
+
+    return;
+}
+
+/**********************************************************************
+ * Close
+ **********************************************************************/
+static void Close( vlc_object_t *p_this )
+{
+    aout_filter_t *p_filter = (aout_filter_t*)p_this;
+    struct aout_filter_sys_t *p_sys = p_filter->p_sys;
+
+    if( p_sys )
+    {
+        if( p_sys->p_last)
+        {
+            free( p_sys->p_last );
+        }
+        free( p_sys );
+    }
+}