src/audio_output/common.c

   1 /*****************************************************************************
   2  * common.c : audio output management of common data structures
   3  *****************************************************************************
   4  * Copyright (C) 2002-2007 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 #ifdef HAVE_CONFIG_H
  24 # include "config.h"
  25 #endif
  26
  27 #include <limits.h>
  28 #include <assert.h>
  29
  30 #include <vlc_common.h>
  31 #include <vlc_aout.h>
  32 #include "aout_internal.h"
  33
  34 /*
  35  * Formats management (internal and external)
  36  */
  37
  38 /*****************************************************************************
  39  * aout_BitsPerSample : get the number of bits per sample
  40  *****************************************************************************/
  41 unsigned int aout_BitsPerSample( vlc_fourcc_t i_format )
  42 {
  43     switch( vlc_fourcc_GetCodec( AUDIO_ES, i_format ) )
  44     {
  45     case VLC_CODEC_U8:
  46     case VLC_CODEC_S8:
  47     case VLC_CODEC_ALAW:
  48     case VLC_CODEC_MULAW:
  49         return 8;
  50
  51     case VLC_CODEC_U16L:
  52     case VLC_CODEC_S16L:
  53     case VLC_CODEC_U16B:
  54     case VLC_CODEC_S16B:
  55         return 16;
  56
  57     case VLC_CODEC_U24L:
  58     case VLC_CODEC_S24L:
  59     case VLC_CODEC_U24B:
  60     case VLC_CODEC_S24B:
  61         return 24;
  62
  63     case VLC_CODEC_S24L32:
  64     case VLC_CODEC_S24B32:
  65     case VLC_CODEC_U32L:
  66     case VLC_CODEC_U32B:
  67     case VLC_CODEC_S32L:
  68     case VLC_CODEC_S32B:
  69     case VLC_CODEC_F32L:
  70     case VLC_CODEC_F32B:
  71         return 32;
  72
  73     case VLC_CODEC_F64L:
  74     case VLC_CODEC_F64B:
  75         return 64;
  76
  77     default:
  78         /* For these formats the caller has to indicate the parameters
  79          * by hand. */
  80         return 0;
  81     }
  82 }
  83
  84 /*****************************************************************************
  85  * aout_FormatPrepare : compute the number of bytes per frame & frame length
  86  *****************************************************************************/
  87 void aout_FormatPrepare( audio_sample_format_t * p_format )
  88 {
  89
  90     unsigned i_channels = aout_FormatNbChannels( p_format );
  91     if( i_channels > 0 )
  92         p_format->i_channels = i_channels;
  93     p_format->i_bitspersample = aout_BitsPerSample( p_format->i_format );
  94     if( p_format->i_bitspersample > 0 )
  95     {
  96         p_format->i_bytes_per_frame = ( p_format->i_bitspersample / 8 )
  97                                     * p_format->i_channels;
  98         p_format->i_frame_length = 1;
  99     }
 100 }
 101
 102 /*****************************************************************************
 103  * aout_FormatPrintChannels : print a channel in a human-readable form
 104  *****************************************************************************/
 105 const char * aout_FormatPrintChannels( const audio_sample_format_t * p_format )
 106 {
 107     if (p_format->channel_type == AUDIO_CHANNEL_TYPE_AMBISONICS)
 108         return "Ambisonics";
 109
 110     /* AUDIO_CHANNEL_TYPE_BITMAP */
 111     switch ( p_format->i_physical_channels )
 112     {
 113     case AOUT_CHAN_LEFT:
 114     case AOUT_CHAN_RIGHT:
 115     case AOUT_CHAN_CENTER:
 116         if ( (p_format->i_physical_channels & AOUT_CHAN_CENTER)
 117               || (p_format->i_physical_channels
 118                    & (AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT)) )
 119             return "Mono";
 120         else if ( p_format->i_physical_channels & AOUT_CHAN_LEFT )
 121             return "Left";
 122         return "Right";
 123     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT:
 124         if ( p_format->i_chan_mode & AOUT_CHANMODE_DOLBYSTEREO )
 125             return "Dolby";
 126         else if ( p_format->i_chan_mode & AOUT_CHANMODE_DUALMONO )
 127             return "Dual-mono";
 128         else if ( p_format->i_physical_channels == AOUT_CHAN_CENTER )
 129             return "Stereo/Mono";
 130         else if ( !(p_format->i_physical_channels & AOUT_CHAN_RIGHT) )
 131             return "Stereo/Left";
 132         else if ( !(p_format->i_physical_channels & AOUT_CHAN_LEFT) )
 133             return "Stereo/Right";
 134         return "Stereo";
 135     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER:
 136         return "3F";
 137     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_REARCENTER:
 138         return "2F1R";
 139     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 140           | AOUT_CHAN_REARCENTER:
 141         return "3F1R";
 142     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 143           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT:
 144         return "2F2R";
 145     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 146           | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT:
 147         return "2F2M";
 148     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 149           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT:
 150         return "3F2R";
 151     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 152           | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT:
 153         return "3F2M";
 154
 155     case AOUT_CHAN_CENTER | AOUT_CHAN_LFE:
 156         if ( (p_format->i_physical_channels & AOUT_CHAN_CENTER)
 157               || (p_format->i_physical_channels
 158                    & (AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT)) )
 159             return "Mono/LFE";
 160         else if ( p_format->i_physical_channels & AOUT_CHAN_LEFT )
 161             return "Left/LFE";
 162         return "Right/LFE";
 163     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_LFE:
 164         if ( p_format->i_chan_mode & AOUT_CHANMODE_DOLBYSTEREO )
 165             return "Dolby/LFE";
 166         else if ( p_format->i_chan_mode & AOUT_CHANMODE_DUALMONO )
 167             return "Dual-mono/LFE";
 168         else if ( p_format->i_physical_channels == AOUT_CHAN_CENTER )
 169             return "Mono/LFE";
 170         else if ( !(p_format->i_physical_channels & AOUT_CHAN_RIGHT) )
 171             return "Stereo/Left/LFE";
 172         else if ( !(p_format->i_physical_channels & AOUT_CHAN_LEFT) )
 173             return "Stereo/Right/LFE";
 174          return "Stereo/LFE";
 175     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER | AOUT_CHAN_LFE:
 176         return "3F/LFE";
 177     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_REARCENTER
 178           | AOUT_CHAN_LFE:
 179         return "2F1R/LFE";
 180     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 181           | AOUT_CHAN_REARCENTER | AOUT_CHAN_LFE:
 182         return "3F1R/LFE";
 183     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 184           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_LFE:
 185         return "2F2R/LFE";
 186     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 187           | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT | AOUT_CHAN_LFE:
 188         return "2F2M/LFE";
 189     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 190           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_LFE:
 191         return "3F2R/LFE";
 192     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 193           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_REARCENTER
 194           | AOUT_CHAN_LFE:
 195         return "3F3R/LFE";
 196     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 197           | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT | AOUT_CHAN_LFE:
 198         return "3F2M/LFE";
 199     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 200           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_MIDDLELEFT
 201           | AOUT_CHAN_MIDDLERIGHT:
 202         return "2F2M2R";
 203     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 204           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_MIDDLELEFT
 205           | AOUT_CHAN_MIDDLERIGHT:
 206         return "3F2M2R";
 207     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 208           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_MIDDLELEFT
 209           | AOUT_CHAN_MIDDLERIGHT | AOUT_CHAN_LFE:
 210         return "3F2M2R/LFE";
 211     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 212           | AOUT_CHAN_REARCENTER | AOUT_CHAN_MIDDLELEFT
 213           | AOUT_CHAN_MIDDLERIGHT | AOUT_CHAN_LFE:
 214         return "3F2M1R/LFE";
 215     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 216           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_REARCENTER
 217           | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT | AOUT_CHAN_LFE:
 218         return "3F2M3R/LFE";
 219     }
 220
 221     return "Unknown-chan-mask";
 222 }
 223
 224 #undef aout_FormatPrint
 225 /**
 226  * Prints an audio sample format in a human-readable form.
 227  */
 228 void aout_FormatPrint( vlc_object_t *obj, const char *psz_text,
 229                        const audio_sample_format_t *p_format )
 230 {
 231     msg_Dbg( obj, "%s '%4.4s' %d Hz %s frame=%u samples/%u bytes", psz_text,
 232              (char *)&p_format->i_format, p_format->i_rate,
 233              aout_FormatPrintChannels( p_format ),
 234              p_format->i_frame_length, p_format->i_bytes_per_frame );
 235 }
 236
 237 #undef aout_FormatsPrint
 238 /**
 239  * Prints two formats in a human-readable form
 240  */
 241 void aout_FormatsPrint( vlc_object_t *obj, const char * psz_text,
 242                         const audio_sample_format_t * p_format1,
 243                         const audio_sample_format_t * p_format2 )
 244 {
 245     msg_Dbg( obj, "%s '%4.4s'->'%4.4s' %u Hz->%u Hz %s->%s",
 246              psz_text,
 247              (char *)&p_format1->i_format, (char *)&p_format2->i_format,
 248              p_format1->i_rate, p_format2->i_rate,
 249              aout_FormatPrintChannels( p_format1 ),
 250              aout_FormatPrintChannels( p_format2 ) );
 251 }
 252
 253 /*****************************************************************************
 254  * aout_CheckChannelReorder : Check if we need to do some channel re-ordering
 255  *****************************************************************************/
 256 unsigned aout_CheckChannelReorder( const uint32_t *chans_in,
 257                                    const uint32_t *chans_out,
 258                                    uint32_t mask, uint8_t *restrict table )
 259 {
 260     static_assert(AOUT_CHAN_MAX <= (sizeof (mask) * CHAR_BIT), "Missing bits");
 261
 262     unsigned channels = 0;
 263
 264     if( chans_in == NULL )
 265         chans_in = pi_vlc_chan_order_wg4;
 266     if( chans_out == NULL )
 267         chans_out = pi_vlc_chan_order_wg4;
 268
 269     for( unsigned i = 0; chans_in[i]; i++ )
 270     {
 271         const uint32_t chan = chans_in[i];
 272         if( !(mask & chan) )
 273             continue;
 274
 275         unsigned index = 0;
 276         for( unsigned j = 0; chan != chans_out[j]; j++ )
 277             if( mask & chans_out[j] )
 278                 index++;
 279
 280         table[channels++] = index;
 281     }
 282
 283     for( unsigned i = 0; i < channels; i++ )
 284         if( table[i] != i )
 285             return channels;
 286     return 0;
 287 }
 288
 289 /**
 290  * Reorders audio samples within a block of linear audio interleaved samples.
 291  * \param ptr start address of the block of samples
 292  * \param bytes size of the block in bytes (must be a multiple of the product
 293  *              of the channels count and the sample size)
 294  * \param channels channels count (also length of the chans_table table)
 295  * \param chans_table permutation table to reorder the channels
 296  *                    (usually computed by aout_CheckChannelReorder())
 297  * \param fourcc sample format (must be a linear sample format)
 298  * \note The samples must be naturally aligned in memory.
 299  */
 300 void aout_ChannelReorder( void *ptr, size_t bytes, uint8_t channels,
 301                           const uint8_t *restrict chans_table, vlc_fourcc_t fourcc )
 302 {
 303     if( unlikely(bytes == 0) )
 304         return;
 305
 306     assert( channels != 0 );
 307
 308     /* The audio formats supported in audio output are inlined. For other
 309      * formats (used in demuxers and muxers), memcpy() is used to avoid
 310      * breaking type punning. */
 311 #define REORDER_TYPE(type) \
 312 do { \
 313     const size_t frames = (bytes / sizeof (type)) / channels; \
 314     type *buf = ptr; \
 315 \
 316     for( size_t i = 0; i < frames; i++ ) \
 317     { \
 318         type tmp[AOUT_CHAN_MAX]; \
 319 \
 320         for( size_t j = 0; j < channels; j++ ) \
 321             tmp[chans_table[j]] = buf[j]; \
 322         memcpy( buf, tmp, sizeof (type) * channels ); \
 323         buf += channels; \
 324     } \
 325 } while(0)
 326
 327     if( likely(channels <= AOUT_CHAN_MAX) )
 328     {
 329         switch( fourcc )
 330         {
 331             case VLC_CODEC_U8:   REORDER_TYPE(uint8_t); return;
 332             case VLC_CODEC_S16N: REORDER_TYPE(int16_t); return;
 333             case VLC_CODEC_FL32: REORDER_TYPE(float);   return;
 334             case VLC_CODEC_S32N: REORDER_TYPE(int32_t); return;
 335             case VLC_CODEC_FL64: REORDER_TYPE(double);  return;
 336         }
 337     }
 338
 339     unsigned size = aout_BitsPerSample( fourcc ) / 8;
 340     assert( size != 0 && size <= 8 );
 341
 342     const size_t frames = bytes / (size * channels);
 343     unsigned char *buf = ptr;
 344
 345     for( size_t i = 0; i < frames; i++ )
 346     {
 347         unsigned char tmp[256 * 8];
 348
 349         for( size_t j = 0; j < channels; j++ )
 350              memcpy( tmp + size * chans_table[j], buf + size * j, size );
 351          memcpy( buf, tmp, size * channels );
 352          buf += size * channels;
 353     }
 354 }
 355
 356 /**
 357  * Interleaves audio samples within a block of samples.
 358  * \param dst destination buffer for interleaved samples
 359  * \param srcv source buffers (one per plane) of uninterleaved samples
 360  * \param samples number of samples (per channel/per plane)
 361  * \param chans channels/planes count
 362  * \param fourcc sample format (must be a linear sample format)
 363  * \note The samples must be naturally aligned in memory.
 364  * \warning Destination and source buffers MUST NOT overlap.
 365  */
 366 void aout_Interleave( void *restrict dst, const void *const *srcv,
 367                       unsigned samples, unsigned chans, vlc_fourcc_t fourcc )
 368 {
 369 #define INTERLEAVE_TYPE(type) \
 370 do { \
 371     type *d = dst; \
 372     for( size_t i = 0; i < chans; i++ ) { \
 373         const type *s = srcv[i]; \
 374         for( size_t j = 0, k = 0; j < samples; j++, k += chans ) \
 375             d[k] = *(s++); \
 376         d++; \
 377     } \
 378 } while(0)
 379
 380     switch( fourcc )
 381     {
 382         case VLC_CODEC_U8:   INTERLEAVE_TYPE(uint8_t);  break;
 383         case VLC_CODEC_S16N: INTERLEAVE_TYPE(int16_t);  break;
 384         case VLC_CODEC_FL32: INTERLEAVE_TYPE(float);    break;
 385         case VLC_CODEC_S32N: INTERLEAVE_TYPE(int32_t);  break;
 386         case VLC_CODEC_FL64: INTERLEAVE_TYPE(double);   break;
 387         default:             vlc_assert_unreachable();
 388     }
 389 #undef INTERLEAVE_TYPE
 390 }
 391
 392 /**
 393  * Deinterleaves audio samples within a block of samples.
 394  * \param dst destination buffer for planar samples
 395  * \param src source buffer with interleaved samples
 396  * \param samples number of samples (per channel/per plane)
 397  * \param chans channels/planes count
 398  * \param fourcc sample format (must be a linear sample format)
 399  * \note The samples must be naturally aligned in memory.
 400  * \warning Destination and source buffers MUST NOT overlap.
 401  */
 402 void aout_Deinterleave( void *restrict dst, const void *restrict src,
 403                       unsigned samples, unsigned chans, vlc_fourcc_t fourcc )
 404 {
 405 #define DEINTERLEAVE_TYPE(type) \
 406 do { \
 407     type *d = dst; \
 408     const type *s = src; \
 409     for( size_t i = 0; i < chans; i++ ) { \
 410         for( size_t j = 0, k = 0; j < samples; j++, k += chans ) \
 411             *(d++) = s[k]; \
 412         s++; \
 413     } \
 414 } while(0)
 415
 416     switch( fourcc )
 417     {
 418         case VLC_CODEC_U8:   DEINTERLEAVE_TYPE(uint8_t);  break;
 419         case VLC_CODEC_S16N: DEINTERLEAVE_TYPE(int16_t);  break;
 420         case VLC_CODEC_FL32: DEINTERLEAVE_TYPE(float);    break;
 421         case VLC_CODEC_S32N: DEINTERLEAVE_TYPE(int32_t);  break;
 422         case VLC_CODEC_FL64: DEINTERLEAVE_TYPE(double);   break;
 423         default:             vlc_assert_unreachable();
 424     }
 425 #undef DEINTERLEAVE_TYPE
 426 }
 427
 428 /*****************************************************************************
 429  * aout_ChannelExtract:
 430  *****************************************************************************/
 431 static inline void ExtractChannel( uint8_t *pi_dst, int i_dst_channels,
 432                                    const uint8_t *pi_src, int i_src_channels,
 433                                    int i_sample_count,
 434                                    const int *pi_selection, int i_bytes )
 435 {
 436     for( int i = 0; i < i_sample_count; i++ )
 437     {
 438         for( int j = 0; j < i_dst_channels; j++ )
 439             memcpy( &pi_dst[j * i_bytes], &pi_src[pi_selection[j] * i_bytes], i_bytes );
 440         pi_dst += i_dst_channels * i_bytes;
 441         pi_src += i_src_channels * i_bytes;
 442     }
 443 }
 444
 445 void aout_ChannelExtract( void *p_dst, int i_dst_channels,
 446                           const void *p_src, int i_src_channels,
 447                           int i_sample_count, const int *pi_selection, int i_bits_per_sample )
 448 {
 449     /* It does not work in place */
 450     assert( p_dst != p_src );
 451
 452     /* Force the compiler to inline for the specific cases so it can optimize */
 453     if( i_bits_per_sample == 8 )
 454         ExtractChannel( p_dst, i_dst_channels, p_src, i_src_channels, i_sample_count, pi_selection, 1 );
 455     else  if( i_bits_per_sample == 16 )
 456         ExtractChannel( p_dst, i_dst_channels, p_src, i_src_channels, i_sample_count, pi_selection, 2 );
 457     else  if( i_bits_per_sample == 32 )
 458         ExtractChannel( p_dst, i_dst_channels, p_src, i_src_channels, i_sample_count, pi_selection, 4 );
 459     else  if( i_bits_per_sample == 64 )
 460         ExtractChannel( p_dst, i_dst_channels, p_src, i_src_channels, i_sample_count, pi_selection, 8 );
 461 }
 462
 463 bool aout_CheckChannelExtraction( int *pi_selection,
 464                                   uint32_t *pi_layout, int *pi_channels,
 465                                   const uint32_t pi_order_dst[AOUT_CHAN_MAX],
 466                                   const uint32_t *pi_order_src, int i_channels )
 467 {
 468     static_assert(AOUT_CHAN_MAX <= (sizeof (*pi_order_dst) * CHAR_BIT),
 469                   "Missing bits");
 470
 471     uint32_t i_layout = 0;
 472     int i_out = 0;
 473     int pi_index[AOUT_CHAN_MAX];
 474
 475     /* */
 476     if( !pi_order_dst )
 477         pi_order_dst = pi_vlc_chan_order_wg4;
 478
 479     /* */
 480     for( int i = 0; i < i_channels; i++ )
 481     {
 482         /* Ignore unknown or duplicated channels or not present in output */
 483         if( !pi_order_src[i] || (i_layout & pi_order_src[i]) )
 484             continue;
 485
 486         for( int j = 0; j < AOUT_CHAN_MAX; j++ )
 487         {
 488             if( pi_order_dst[j] == pi_order_src[i] )
 489             {
 490                 assert( i_out < AOUT_CHAN_MAX );
 491                 pi_index[i_out++] = i;
 492                 i_layout |= pi_order_src[i];
 493                 break;
 494             }
 495         }
 496     }
 497
 498     /* */
 499     for( int i = 0, j = 0; i < AOUT_CHAN_MAX; i++ )
 500     {
 501         for( int k = 0; k < i_out; k++ )
 502         {
 503             if( pi_order_dst[i] == pi_order_src[pi_index[k]] )
 504             {
 505                 pi_selection[j++] = pi_index[k];
 506                 break;
 507             }
 508         }
 509     }
 510
 511     *pi_layout = i_layout;
 512     *pi_channels = i_out;
 513
 514     for( int i = 0; i < i_out; i++ )
 515     {
 516         if( pi_selection[i] != i )
 517             return true;
 518     }
 519     return i_out != i_channels;
 520 }
 521
 522 /* Return the order in which filters should be inserted */
 523 static int FilterOrder( const char *psz_name )
 524 {
 525     static const struct {
 526         const char psz_name[10];
 527         int        i_order;
 528     } filter[] = {
 529         { "equalizer",  0 },
 530     };
 531     for( unsigned i = 0; i < ARRAY_SIZE(filter); i++ )
 532     {
 533         if( !strcmp( filter[i].psz_name, psz_name ) )
 534             return filter[i].i_order;
 535     }
 536     return INT_MAX;
 537 }
 538
 539 int aout_EnableFilter( audio_output_t *p_aout, const char *psz_name, bool b_add )
 540 {
 541     if( *psz_name == '\0' )
 542         return VLC_EGENERIC;
 543
 544     const char *psz_variable = "audio-filter";
 545     char *psz_list;
 546     psz_list = var_GetString( p_aout, psz_variable );
 547
 548     /* Split the string into an array of filters */
 549     int i_count = 1;
 550     for( char *p = psz_list; p && *p; p++ )
 551         i_count += *p == ':';
 552     i_count += b_add;
 553
 554     const char **ppsz_filter = calloc( i_count, sizeof(*ppsz_filter) );
 555     if( !ppsz_filter )
 556     {
 557         free( psz_list );
 558         return VLC_ENOMEM;
 559     }
 560     bool b_present = false;
 561     i_count = 0;
 562     for( char *p = psz_list; p && *p; )
 563     {
 564         char *psz_end = strchr(p, ':');
 565         if( psz_end )
 566             *psz_end++ = '\0';
 567         else
 568             psz_end = p + strlen(p);
 569         if( *p )
 570         {
 571             b_present |= !strcmp( p, psz_name );
 572             ppsz_filter[i_count++] = p;
 573         }
 574         p = psz_end;
 575     }
 576     if( b_present == b_add )
 577     {
 578         free( ppsz_filter );
 579         free( psz_list );
 580         return VLC_EGENERIC;
 581     }
 582
 583     if( b_add )
 584     {
 585         int i_order = FilterOrder( psz_name );
 586         int i;
 587         for( i = 0; i < i_count; i++ )
 588         {
 589             if( FilterOrder( ppsz_filter[i] ) > i_order )
 590                 break;
 591         }
 592         if( i < i_count )
 593             memmove( &ppsz_filter[i+1], &ppsz_filter[i], (i_count - i) * sizeof(*ppsz_filter) );
 594         ppsz_filter[i] = psz_name;
 595         i_count++;
 596     }
 597     else
 598     {
 599         for( int i = 0; i < i_count; i++ )
 600         {
 601             if( !strcmp( ppsz_filter[i], psz_name ) )
 602                 ppsz_filter[i] = "";
 603         }
 604     }
 605     size_t i_length = 0;
 606     for( int i = 0; i < i_count; i++ )
 607         i_length += 1 + strlen( ppsz_filter[i] );
 608
 609     char *psz_new = malloc( i_length + 1 );
 610
 611     if( unlikely( !psz_new ) )
 612     {
 613         free( ppsz_filter );
 614         free( psz_list );
 615         return VLC_ENOMEM;
 616     }
 617
 618     *psz_new = '\0';
 619     for( int i = 0; i < i_count; i++ )
 620     {
 621         if( *ppsz_filter[i] == '\0' )
 622             continue;
 623         if( *psz_new )
 624             strcat( psz_new, ":" );
 625         strcat( psz_new, ppsz_filter[i] );
 626     }
 627     free( ppsz_filter );
 628     free( psz_list );
 629
 630     var_SetString( p_aout, psz_variable, psz_new );
 631     free( psz_new );
 632
 633     return VLC_SUCCESS;
 634 }