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, 2014 VLC authors and VideoLAN
   5  *
   6  * Authors: Christophe Massiot <massiot@via.ecp.fr>
   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 <assert.h>
  32
  33 #include <vlc_common.h>
  34 #include <vlc_plugin.h>
  35 #include <vlc_aout.h>
  36 #include <vlc_filter.h>
  37
  38 static int Create( vlc_object_t * );
  39
  40 vlc_module_begin ()
  41     set_description( N_("Audio filter for trivial channel mixing") )
  42     set_capability( "audio converter", 1 )
  43     set_category( CAT_AUDIO )
  44     set_subcategory( SUBCAT_AUDIO_MISC )
  45     set_callbacks( Create, NULL )
  46 vlc_module_end ()
  47
  48 /**
  49  * Trivially upmixes
  50  */
  51 static block_t *Upmix( filter_t *p_filter, block_t *p_in_buf )
  52 {
  53     unsigned i_input_nb = aout_FormatNbChannels( &p_filter->fmt_in.audio );
  54     unsigned i_output_nb = aout_FormatNbChannels( &p_filter->fmt_out.audio );
  55
  56     assert( i_input_nb < i_output_nb );
  57
  58     block_t *p_out_buf = block_Alloc(
  59                               p_in_buf->i_buffer * i_output_nb / i_input_nb );
  60     if( unlikely(p_out_buf == NULL) )
  61     {
  62         block_Release( p_in_buf );
  63         return NULL;
  64     }
  65
  66     p_out_buf->i_nb_samples = p_in_buf->i_nb_samples;
  67     p_out_buf->i_dts        = p_in_buf->i_dts;
  68     p_out_buf->i_pts        = p_in_buf->i_pts;
  69     p_out_buf->i_length     = p_in_buf->i_length;
  70
  71     float *p_dest = (float *)p_out_buf->p_buffer;
  72     const float *p_src = (float *)p_in_buf->p_buffer;
  73
  74     for( size_t i = 0; i < p_in_buf->i_nb_samples; i++ )
  75     {
  76         for( unsigned j = 0; j < i_output_nb; j++ )
  77             p_dest[j] = p_src[j % i_input_nb];
  78
  79         p_src += i_input_nb;
  80         p_dest += i_output_nb;
  81     }
  82
  83     block_Release( p_in_buf );
  84     return p_out_buf;
  85 }
  86
  87 /**
  88  * Trivially downmixes (i.e. drop extra channels)
  89  */
  90 static block_t *Downmix( filter_t *p_filter, block_t *p_buf )
  91 {
  92     unsigned i_input_nb = aout_FormatNbChannels( &p_filter->fmt_in.audio );
  93     unsigned i_output_nb = aout_FormatNbChannels( &p_filter->fmt_out.audio );
  94
  95     assert( i_input_nb >= i_output_nb );
  96
  97     float *p_dest = (float *)p_buf->p_buffer;
  98     const float *p_src = p_dest;
  99
 100     for( size_t i = 0; i < p_buf->i_nb_samples; i++ )
 101     {
 102         for( unsigned j = 0; j < i_output_nb; j++ )
 103             p_dest[j] = p_src[j];
 104
 105         p_src += i_input_nb;
 106         p_dest += i_output_nb;
 107     }
 108
 109     return p_buf;
 110 }
 111
 112 static block_t *CopyLeft( filter_t *p_filter, block_t *p_buf )
 113 {
 114     float *p = (float *)p_buf->p_buffer;
 115
 116     for( unsigned i = 0; i < p_buf->i_nb_samples; i++ )
 117     {
 118         p[1] = p[0];
 119         p += 2;
 120     }
 121     (void) p_filter;
 122     return p_buf;
 123 }
 124
 125 static block_t *CopyRight( filter_t *p_filter, block_t *p_buf )
 126 {
 127     float *p = (float *)p_buf->p_buffer;
 128
 129     for( unsigned i = 0; i < p_buf->i_nb_samples; i++ )
 130     {
 131         p[0] = p[1];
 132         p += 2;
 133     }
 134     (void) p_filter;
 135     return p_buf;
 136 }
 137
 138 static block_t *ExtractLeft( filter_t *p_filter, block_t *p_buf )
 139 {
 140     float *p_dest = (float *)p_buf->p_buffer;
 141     const float *p_src = p_dest;
 142
 143     for( unsigned i = 0; i < p_buf->i_nb_samples; i++ )
 144     {
 145         *(p_dest++) = *p_src;
 146         p_src += 2;
 147     }
 148     (void) p_filter;
 149     return p_buf;
 150 }
 151
 152 static block_t *ExtractRight( filter_t *p_filter, block_t *p_buf )
 153 {
 154     float *p_dest = (float *)p_buf->p_buffer;
 155     const float *p_src = p_dest;
 156
 157     for( unsigned i = 0; i < p_buf->i_nb_samples; i++ )
 158     {
 159         p_src++;
 160         *(p_dest++) = *(p_src++);
 161     }
 162     (void) p_filter;
 163     return p_buf;
 164 }
 165
 166 static block_t *ReverseStereo( filter_t *p_filter, block_t *p_buf )
 167 {
 168     float *p = (float *)p_buf->p_buffer;
 169
 170     /* Reverse-stereo mode */
 171     for( unsigned i = 0; i < p_buf->i_nb_samples; i++ )
 172     {
 173         float f = p[0];
 174         p[0] = p[1];
 175         p[1] = f;
 176         p += 2;
 177     }
 178     (void) p_filter;
 179     return p_buf;
 180 }
 181
 182 /**
 183  * Probes the trivial channel mixer
 184  */
 185 static int Create( vlc_object_t *p_this )
 186 {
 187     filter_t *p_filter = (filter_t *)p_this;
 188     const audio_format_t *infmt = &p_filter->fmt_in.audio;
 189     const audio_format_t *outfmt = &p_filter->fmt_out.audio;
 190
 191     if( infmt->i_format != outfmt->i_format
 192      || infmt->i_rate != outfmt->i_rate
 193      || infmt->i_format != VLC_CODEC_FL32 )
 194         return VLC_EGENERIC;
 195     if( infmt->i_physical_channels == outfmt->i_physical_channels
 196      && infmt->i_original_channels == outfmt->i_original_channels )
 197         return VLC_EGENERIC;
 198
 199     if( outfmt->i_physical_channels == AOUT_CHANS_STEREO )
 200     {
 201         bool swap = (outfmt->i_original_channels & AOUT_CHAN_REVERSESTEREO)
 202                   != (infmt->i_original_channels & AOUT_CHAN_REVERSESTEREO);
 203
 204         if( (outfmt->i_original_channels & AOUT_CHAN_PHYSMASK)
 205                                                             == AOUT_CHAN_LEFT )
 206         {
 207             p_filter->pf_audio_filter = swap ? CopyRight : CopyLeft;
 208             return VLC_SUCCESS;
 209         }
 210
 211         if( (outfmt->i_original_channels & AOUT_CHAN_PHYSMASK)
 212                                                            == AOUT_CHAN_RIGHT )
 213         {
 214             p_filter->pf_audio_filter = swap ? CopyLeft : CopyRight;
 215             return VLC_SUCCESS;
 216         }
 217
 218         if( swap )
 219         {
 220             p_filter->pf_audio_filter = ReverseStereo;
 221             return VLC_SUCCESS;
 222         }
 223     }
 224
 225     if ( aout_FormatNbChannels( outfmt ) == 1 )
 226     {
 227         bool mono = !!(infmt->i_original_channels & AOUT_CHAN_DUALMONO);
 228
 229         if( mono && (infmt->i_original_channels & AOUT_CHAN_LEFT) )
 230         {
 231             p_filter->pf_audio_filter = ExtractLeft;
 232             return VLC_SUCCESS;
 233         }
 234
 235         if( mono && (infmt->i_original_channels & AOUT_CHAN_RIGHT) )
 236         {
 237             p_filter->pf_audio_filter = ExtractRight;
 238             return VLC_SUCCESS;
 239         }
 240     }
 241
 242     if( aout_FormatNbChannels( outfmt ) > aout_FormatNbChannels( infmt ) )
 243         p_filter->pf_audio_filter = Upmix;
 244     else
 245         p_filter->pf_audio_filter = Downmix;
 246
 247     return VLC_SUCCESS;
 248 }