git.sesse.net Git - vlc/blob - modules/audio_filter/channel_mixer/trivial.c

   1 /*****************************************************************************
   2  * trivial.c : trivial channel mixer plug-in (drops unwanted channels)
   3  *****************************************************************************
   4  * Copyright (C) 2002, 2006 the VideoLAN team
   5  * $Id$
   6  *
   7  * Authors: Christophe Massiot <massiot@via.ecp.fr>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  22  *****************************************************************************/
  23
  24 /*****************************************************************************
  25  * Preamble
  26  *****************************************************************************/
  27
  28 #ifdef HAVE_CONFIG_H
  29 # include "config.h"
  30 #endif
  31
  32 #include <vlc_common.h>
  33 #include <vlc_plugin.h>
  34 #include <vlc_aout.h>
  35 #include <vlc_filter.h>
  36
  37 /*****************************************************************************
  38  * Local prototypes
  39  *****************************************************************************/
  40 static int  Create    ( vlc_object_t * );
  41
  42 static block_t *DoWork( filter_t *, block_t * );
  43
  44 /*****************************************************************************
  45  * Module descriptor
  46  *****************************************************************************/
  47 vlc_module_begin ()
  48     set_description( N_("Audio filter for trivial channel mixing") )
  49     set_capability( "audio filter", 1 )
  50     set_category( CAT_AUDIO )
  51     set_subcategory( SUBCAT_AUDIO_MISC )
  52     set_callbacks( Create, NULL )
  53 vlc_module_end ()
  54
  55 /*****************************************************************************
  56  * Create: allocate trivial channel mixer
  57  *****************************************************************************/
  58 static int Create( vlc_object_t *p_this )
  59 {
  60     filter_t * p_filter = (filter_t *)p_this;
  61
  62     if ( (p_filter->fmt_in.audio.i_physical_channels
  63            == p_filter->fmt_out.audio.i_physical_channels
  64            && p_filter->fmt_in.audio.i_original_channels
  65                == p_filter->fmt_out.audio.i_original_channels)
  66           || p_filter->fmt_in.audio.i_format != p_filter->fmt_out.audio.i_format
  67           || p_filter->fmt_in.audio.i_rate != p_filter->fmt_out.audio.i_rate
  68           || (p_filter->fmt_in.audio.i_format != VLC_CODEC_FL32
  69                && p_filter->fmt_in.audio.i_format != VLC_CODEC_FI32) )
  70     {
  71         return VLC_EGENERIC;
  72     }
  73
  74     p_filter->pf_audio_filter = DoWork;
  75     return VLC_SUCCESS;
  76 }
  77
  78 /*****************************************************************************
  79  * SparseCopy: trivially downmix or upmix a buffer
  80  *****************************************************************************/
  81 static void SparseCopy( int32_t * p_dest, const int32_t * p_src, size_t i_len,
  82                         int i_output_stride, int i_input_stride )
  83 {
  84     int i;
  85     for ( i = i_len; i--; )
  86     {
  87         int j;
  88         for ( j = 0; j < i_output_stride; j++ )
  89         {
  90             p_dest[j] = p_src[j % i_input_stride];
  91         }
  92         p_src += i_input_stride;
  93         p_dest += i_output_stride;
  94     }
  95 }
  96
  97 /*****************************************************************************
  98  * DoWork: convert a buffer
  99  *****************************************************************************/
 100 static block_t *DoWork( filter_t * p_filter, block_t * p_in_buf )
 101 {
 102     int i_input_nb = aout_FormatNbChannels( &p_filter->fmt_in.audio );
 103     int i_output_nb = aout_FormatNbChannels( &p_filter->fmt_out.audio );
 104
 105     block_t *p_out_buf;
 106     if( i_input_nb >= i_output_nb )
 107     {
 108         p_out_buf = p_in_buf; /* mix in place */
 109         p_out_buf->i_buffer = p_in_buf->i_buffer / i_input_nb * i_output_nb;
 110     }
 111     else
 112     {
 113         p_out_buf = filter_NewAudioBuffer( p_filter,
 114                               p_in_buf->i_buffer / i_input_nb * i_output_nb );
 115         if( !p_out_buf )
 116             goto out;
 117         p_out_buf->i_nb_samples = p_in_buf->i_nb_samples;
 118     }
 119
 120     int32_t * p_dest = (int32_t *)p_out_buf->p_buffer;
 121     const int32_t * p_src = (int32_t *)p_in_buf->p_buffer;
 122
 123     if ( (p_filter->fmt_out.audio.i_original_channels & AOUT_CHAN_PHYSMASK)
 124                 != (p_filter->fmt_in.audio.i_original_channels & AOUT_CHAN_PHYSMASK)
 125            && (p_filter->fmt_in.audio.i_original_channels & AOUT_CHAN_PHYSMASK)
 126                 == (AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT) )
 127     {
 128         int i;
 129         /* This is a bit special. */
 130         if ( !(p_filter->fmt_out.audio.i_original_channels & AOUT_CHAN_LEFT) )
 131         {
 132             p_src++;
 133         }
 134         if ( p_filter->fmt_out.audio.i_physical_channels == AOUT_CHAN_CENTER )
 135         {
 136             /* Mono mode */
 137             for ( i = p_in_buf->i_nb_samples; i--; )
 138             {
 139                 *p_dest = *p_src;
 140                 p_dest++;
 141                 p_src += 2;
 142             }
 143         }
 144         else
 145         {
 146             /* Fake-stereo mode */
 147             for ( i = p_in_buf->i_nb_samples; i--; )
 148             {
 149                 *p_dest = *p_src;
 150                 p_dest++;
 151                 *p_dest = *p_src;
 152                 p_dest++;
 153                 p_src += 2;
 154             }
 155         }
 156     }
 157     else if ( p_filter->fmt_out.audio.i_original_channels
 158                                     & AOUT_CHAN_REVERSESTEREO )
 159     {
 160         /* Reverse-stereo mode */
 161         int i;
 162         for ( i = p_in_buf->i_nb_samples; i--; )
 163         {
 164             int32_t i_tmp = p_src[0];
 165             p_dest[0] = p_src[1];
 166             p_dest[1] = i_tmp;
 167
 168             p_dest += 2;
 169             p_src += 2;
 170         }
 171     }
 172     else
 173     {
 174         SparseCopy( p_dest, p_src, p_in_buf->i_nb_samples, i_output_nb,
 175                     i_input_nb );
 176     }
 177 out:
 178     if( p_in_buf != p_out_buf )
 179         block_Release( p_in_buf );
 180     return p_out_buf;
 181 }
 182