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  * $Id$
   6  *
   7  * Authors: Christophe Massiot <massiot@via.ecp.fr>
   8  *
   9  * This program is free software; you can redistribute it and/or modify it
  10  * under the terms of the GNU Lesser General Public License as published by
  11  * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public License
  20  * along with this program; if not, write to the Free Software Foundation,
  21  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  22  *****************************************************************************/
  23
  24 #ifdef HAVE_CONFIG_H
  25 # include "config.h"
  26 #endif
  27
  28 #include <limits.h>
  29 #include <assert.h>
  30
  31 #include <vlc_common.h>
  32 #include <vlc_aout.h>
  33 #include "aout_internal.h"
  34
  35 /*
  36  * Formats management (internal and external)
  37  */
  38
  39 /*****************************************************************************
  40  * aout_BitsPerSample : get the number of bits per sample
  41  *****************************************************************************/
  42 unsigned int aout_BitsPerSample( vlc_fourcc_t i_format )
  43 {
  44     switch( vlc_fourcc_GetCodec( AUDIO_ES, i_format ) )
  45     {
  46     case VLC_CODEC_U8:
  47     case VLC_CODEC_S8:
  48     case VLC_CODEC_ALAW:
  49     case VLC_CODEC_MULAW:
  50         return 8;
  51
  52     case VLC_CODEC_U16L:
  53     case VLC_CODEC_S16L:
  54     case VLC_CODEC_U16B:
  55     case VLC_CODEC_S16B:
  56         return 16;
  57
  58     case VLC_CODEC_U24L:
  59     case VLC_CODEC_S24L:
  60     case VLC_CODEC_U24B:
  61     case VLC_CODEC_S24B:
  62         return 24;
  63
  64     case VLC_CODEC_S24L32:
  65     case VLC_CODEC_S24B32:
  66     case VLC_CODEC_U32L:
  67     case VLC_CODEC_U32B:
  68     case VLC_CODEC_S32L:
  69     case VLC_CODEC_S32B:
  70     case VLC_CODEC_F32L:
  71     case VLC_CODEC_F32B:
  72         return 32;
  73
  74     case VLC_CODEC_F64L:
  75     case VLC_CODEC_F64B:
  76         return 64;
  77
  78     default:
  79         /* For these formats the caller has to indicate the parameters
  80          * by hand. */
  81         return 0;
  82     }
  83 }
  84
  85 /*****************************************************************************
  86  * aout_FormatPrepare : compute the number of bytes per frame & frame length
  87  *****************************************************************************/
  88 void aout_FormatPrepare( audio_sample_format_t * p_format )
  89 {
  90
  91     unsigned i_channels = aout_FormatNbChannels( p_format );
  92     if( i_channels > 0 )
  93         p_format->i_channels = i_channels;
  94     p_format->i_bitspersample = aout_BitsPerSample( p_format->i_format );
  95     if( p_format->i_bitspersample > 0 )
  96     {
  97         p_format->i_bytes_per_frame = ( p_format->i_bitspersample / 8 )
  98                                     * p_format->i_channels;
  99         p_format->i_frame_length = 1;
 100     }
 101 }
 102
 103 /*****************************************************************************
 104  * aout_FormatPrintChannels : print a channel in a human-readable form
 105  *****************************************************************************/
 106 const char * aout_FormatPrintChannels( const audio_sample_format_t * p_format )
 107 {
 108     if (p_format->channel_type == AUDIO_CHANNEL_TYPE_AMBISONICS)
 109         return "Ambisonics";
 110
 111     /* AUDIO_CHANNEL_TYPE_BITMAP */
 112     switch ( p_format->i_physical_channels )
 113     {
 114     case AOUT_CHAN_LEFT:
 115     case AOUT_CHAN_RIGHT:
 116     case AOUT_CHAN_CENTER:
 117         if ( (p_format->i_physical_channels & AOUT_CHAN_CENTER)
 118               || (p_format->i_physical_channels
 119                    & (AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT)) )
 120             return "Mono";
 121         else if ( p_format->i_physical_channels & AOUT_CHAN_LEFT )
 122             return "Left";
 123         return "Right";
 124     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT:
 125         if ( p_format->i_chan_mode & AOUT_CHANMODE_DOLBYSTEREO )
 126             return "Dolby";
 127         else if ( p_format->i_chan_mode & AOUT_CHANMODE_DUALMONO )
 128             return "Dual-mono";
 129         else if ( p_format->i_physical_channels == AOUT_CHAN_CENTER )
 130             return "Stereo/Mono";
 131         else if ( !(p_format->i_physical_channels & AOUT_CHAN_RIGHT) )
 132             return "Stereo/Left";
 133         else if ( !(p_format->i_physical_channels & AOUT_CHAN_LEFT) )
 134             return "Stereo/Right";
 135         return "Stereo";
 136     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER:
 137         return "3F";
 138     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_REARCENTER:
 139         return "2F1R";
 140     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 141           | AOUT_CHAN_REARCENTER:
 142         return "3F1R";
 143     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 144           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT:
 145         return "2F2R";
 146     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 147           | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT:
 148         return "2F2M";
 149     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 150           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT:
 151         return "3F2R";
 152     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 153           | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT:
 154         return "3F2M";
 155
 156     case AOUT_CHAN_CENTER | AOUT_CHAN_LFE:
 157         if ( (p_format->i_physical_channels & AOUT_CHAN_CENTER)
 158               || (p_format->i_physical_channels
 159                    & (AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT)) )
 160             return "Mono/LFE";
 161         else if ( p_format->i_physical_channels & AOUT_CHAN_LEFT )
 162             return "Left/LFE";
 163         return "Right/LFE";
 164     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_LFE:
 165         if ( p_format->i_chan_mode & AOUT_CHANMODE_DOLBYSTEREO )
 166             return "Dolby/LFE";
 167         else if ( p_format->i_chan_mode & AOUT_CHANMODE_DUALMONO )
 168             return "Dual-mono/LFE";
 169         else if ( p_format->i_physical_channels == AOUT_CHAN_CENTER )
 170             return "Mono/LFE";
 171         else if ( !(p_format->i_physical_channels & AOUT_CHAN_RIGHT) )
 172             return "Stereo/Left/LFE";
 173         else if ( !(p_format->i_physical_channels & AOUT_CHAN_LEFT) )
 174             return "Stereo/Right/LFE";
 175          return "Stereo/LFE";
 176     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER | AOUT_CHAN_LFE:
 177         return "3F/LFE";
 178     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_REARCENTER
 179           | AOUT_CHAN_LFE:
 180         return "2F1R/LFE";
 181     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 182           | AOUT_CHAN_REARCENTER | AOUT_CHAN_LFE:
 183         return "3F1R/LFE";
 184     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 185           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_LFE:
 186         return "2F2R/LFE";
 187     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 188           | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT | AOUT_CHAN_LFE:
 189         return "2F2M/LFE";
 190     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 191           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_LFE:
 192         return "3F2R/LFE";
 193     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 194           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_REARCENTER
 195           | AOUT_CHAN_LFE:
 196         return "3F3R/LFE";
 197     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 198           | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT | AOUT_CHAN_LFE:
 199         return "3F2M/LFE";
 200     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
 201           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_MIDDLELEFT
 202           | AOUT_CHAN_MIDDLERIGHT:
 203         return "2F2M2R";
 204     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 205           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_MIDDLELEFT
 206           | AOUT_CHAN_MIDDLERIGHT:
 207         return "3F2M2R";
 208     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 209           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_MIDDLELEFT
 210           | AOUT_CHAN_MIDDLERIGHT | AOUT_CHAN_LFE:
 211         return "3F2M2R/LFE";
 212     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 213           | AOUT_CHAN_REARCENTER | AOUT_CHAN_MIDDLELEFT
 214           | AOUT_CHAN_MIDDLERIGHT | AOUT_CHAN_LFE:
 215         return "3F2M1R/LFE";
 216     case AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
 217           | AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT | AOUT_CHAN_REARCENTER
 218           | AOUT_CHAN_MIDDLELEFT | AOUT_CHAN_MIDDLERIGHT | AOUT_CHAN_LFE:
 219         return "3F2M3R/LFE";
 220     }
 221
 222     return "Unknown-chan-mask";
 223 }
 224
 225 #undef aout_FormatPrint
 226 /**
 227  * Prints an audio sample format in a human-readable form.
 228  */
 229 void aout_FormatPrint( vlc_object_t *obj, const char *psz_text,
 230                        const audio_sample_format_t *p_format )
 231 {
 232     msg_Dbg( obj, "%s '%4.4s' %d Hz %s frame=%u samples/%u bytes", psz_text,
 233              (char *)&p_format->i_format, p_format->i_rate,
 234              aout_FormatPrintChannels( p_format ),
 235              p_format->i_frame_length, p_format->i_bytes_per_frame );
 236 }
 237
 238 #undef aout_FormatsPrint
 239 /**
 240  * Prints two formats in a human-readable form
 241  */
 242 void aout_FormatsPrint( vlc_object_t *obj, const char * psz_text,
 243                         const audio_sample_format_t * p_format1,
 244                         const audio_sample_format_t * p_format2 )
 245 {
 246     msg_Dbg( obj, "%s '%4.4s'->'%4.4s' %u Hz->%u Hz %s->%s",
 247              psz_text,
 248              (char *)&p_format1->i_format, (char *)&p_format2->i_format,
 249              p_format1->i_rate, p_format2->i_rate,
 250              aout_FormatPrintChannels( p_format1 ),
 251              aout_FormatPrintChannels( p_format2 ) );
 252 }
 253
 254 /*****************************************************************************
 255  * aout_CheckChannelReorder : Check if we need to do some channel re-ordering
 256  *****************************************************************************/
 257 unsigned aout_CheckChannelReorder( const uint32_t *chans_in,
 258                                    const uint32_t *chans_out,
 259                                    uint32_t mask, uint8_t *restrict table )
 260 {
 261     static_assert(AOUT_CHAN_MAX <= (sizeof (mask) * CHAR_BIT), "Missing bits");
 262
 263     unsigned channels = 0;
 264
 265     if( chans_in == NULL )
 266         chans_in = pi_vlc_chan_order_wg4;
 267     if( chans_out == NULL )
 268         chans_out = pi_vlc_chan_order_wg4;
 269
 270     for( unsigned i = 0; chans_in[i]; i++ )
 271     {
 272         const uint32_t chan = chans_in[i];
 273         if( !(mask & chan) )
 274             continue;
 275
 276         unsigned index = 0;
 277         for( unsigned j = 0; chan != chans_out[j]; j++ )
 278             if( mask & chans_out[j] )
 279                 index++;
 280
 281         table[channels++] = index;
 282     }
 283
 284     for( unsigned i = 0; i < channels; i++ )
 285         if( table[i] != i )
 286             return channels;
 287     return 0;
 288 }
 289
 290 /**
 291  * Reorders audio samples within a block of linear audio interleaved samples.
 292  * \param ptr start address of the block of samples
 293  * \param bytes size of the block in bytes (must be a multiple of the product
 294  *              of the channels count and the sample size)
 295  * \param channels channels count (also length of the chans_table table)
 296  * \param chans_table permutation table to reorder the channels
 297  *                    (usually computed by aout_CheckChannelReorder())
 298  * \param fourcc sample format (must be a linear sample format)
 299  * \note The samples must be naturally aligned in memory.
 300  */
 301 void aout_ChannelReorder( void *ptr, size_t bytes, uint8_t channels,
 302                           const uint8_t *restrict chans_table, vlc_fourcc_t fourcc )
 303 {
 304     if( unlikely(bytes == 0) )
 305         return;
 306
 307     assert( channels != 0 );
 308
 309     /* The audio formats supported in audio output are inlined. For other
 310      * formats (used in demuxers and muxers), memcpy() is used to avoid
 311      * breaking type punning. */
 312 #define REORDER_TYPE(type) \
 313 do { \
 314     const size_t frames = (bytes / sizeof (type)) / channels; \
 315     type *buf = ptr; \
 316 \
 317     for( size_t i = 0; i < frames; i++ ) \
 318     { \
 319         type tmp[AOUT_CHAN_MAX]; \
 320 \
 321         for( size_t j = 0; j < channels; j++ ) \
 322             tmp[chans_table[j]] = buf[j]; \
 323         memcpy( buf, tmp, sizeof (type) * channels ); \
 324         buf += channels; \
 325     } \
 326 } while(0)
 327
 328     if( likely(channels <= AOUT_CHAN_MAX) )
 329     {
 330         switch( fourcc )
 331         {
 332             case VLC_CODEC_U8:   REORDER_TYPE(uint8_t); return;
 333             case VLC_CODEC_S16N: REORDER_TYPE(int16_t); return;
 334             case VLC_CODEC_FL32: REORDER_TYPE(float);   return;
 335             case VLC_CODEC_S32N: REORDER_TYPE(int32_t); return;
 336             case VLC_CODEC_FL64: REORDER_TYPE(double);  return;
 337         }
 338     }
 339
 340     unsigned size = aout_BitsPerSample( fourcc ) / 8;
 341     assert( size != 0 && size <= 8 );
 342
 343     const size_t frames = bytes / (size * channels);
 344     unsigned char *buf = ptr;
 345
 346     for( size_t i = 0; i < frames; i++ )
 347     {
 348         unsigned char tmp[256 * 8];
 349
 350         for( size_t j = 0; j < channels; j++ )
 351              memcpy( tmp + size * chans_table[j], buf + size * j, size );
 352          memcpy( buf, tmp, size * channels );
 353          buf += size * channels;
 354     }
 355 }
 356
 357 /**
 358  * Interleaves audio samples within a block of samples.
 359  * \param dst destination buffer for interleaved samples
 360  * \param srcv source buffers (one per plane) of uninterleaved samples
 361  * \param samples number of samples (per channel/per plane)
 362  * \param chans channels/planes count
 363  * \param fourcc sample format (must be a linear sample format)
 364  * \note The samples must be naturally aligned in memory.
 365  * \warning Destination and source buffers MUST NOT overlap.
 366  */
 367 void aout_Interleave( void *restrict dst, const void *const *srcv,
 368                       unsigned samples, unsigned chans, vlc_fourcc_t fourcc )
 369 {
 370 #define INTERLEAVE_TYPE(type) \
 371 do { \
 372     type *d = dst; \
 373     for( size_t i = 0; i < chans; i++ ) { \
 374         const type *s = srcv[i]; \
 375         for( size_t j = 0, k = 0; j < samples; j++, k += chans ) \
 376             d[k] = *(s++); \
 377         d++; \
 378     } \
 379 } while(0)
 380
 381     switch( fourcc )
 382     {
 383         case VLC_CODEC_U8:   INTERLEAVE_TYPE(uint8_t);  break;
 384         case VLC_CODEC_S16N: INTERLEAVE_TYPE(int16_t);  break;
 385         case VLC_CODEC_FL32: INTERLEAVE_TYPE(float);    break;
 386         case VLC_CODEC_S32N: INTERLEAVE_TYPE(int32_t);  break;
 387         case VLC_CODEC_FL64: INTERLEAVE_TYPE(double);   break;
 388         default:             vlc_assert_unreachable();
 389     }
 390 #undef INTERLEAVE_TYPE
 391 }
 392
 393 /**
 394  * Deinterleaves audio samples within a block of samples.
 395  * \param dst destination buffer for planar samples
 396  * \param src source buffer with interleaved samples
 397  * \param samples number of samples (per channel/per plane)
 398  * \param chans channels/planes count
 399  * \param fourcc sample format (must be a linear sample format)
 400  * \note The samples must be naturally aligned in memory.
 401  * \warning Destination and source buffers MUST NOT overlap.
 402  */
 403 void aout_Deinterleave( void *restrict dst, const void *restrict src,
 404                       unsigned samples, unsigned chans, vlc_fourcc_t fourcc )
 405 {
 406 #define DEINTERLEAVE_TYPE(type) \
 407 do { \
 408     type *d = dst; \
 409     const type *s = src; \
 410     for( size_t i = 0; i < chans; i++ ) { \
 411         for( size_t j = 0, k = 0; j < samples; j++, k += chans ) \
 412             *(d++) = s[k]; \
 413         s++; \
 414     } \
 415 } while(0)
 416
 417     switch( fourcc )
 418     {
 419         case VLC_CODEC_U8:   DEINTERLEAVE_TYPE(uint8_t);  break;
 420         case VLC_CODEC_S16N: DEINTERLEAVE_TYPE(int16_t);  break;
 421         case VLC_CODEC_FL32: DEINTERLEAVE_TYPE(float);    break;
 422         case VLC_CODEC_S32N: DEINTERLEAVE_TYPE(int32_t);  break;
 423         case VLC_CODEC_FL64: DEINTERLEAVE_TYPE(double);   break;
 424         default:             vlc_assert_unreachable();
 425     }
 426 #undef DEINTERLEAVE_TYPE
 427 }
 428
 429 /*****************************************************************************
 430  * aout_ChannelExtract:
 431  *****************************************************************************/
 432 static inline void ExtractChannel( uint8_t *pi_dst, int i_dst_channels,
 433                                    const uint8_t *pi_src, int i_src_channels,
 434                                    int i_sample_count,
 435                                    const int *pi_selection, int i_bytes )
 436 {
 437     for( int i = 0; i < i_sample_count; i++ )
 438     {
 439         for( int j = 0; j < i_dst_channels; j++ )
 440             memcpy( &pi_dst[j * i_bytes], &pi_src[pi_selection[j] * i_bytes], i_bytes );
 441         pi_dst += i_dst_channels * i_bytes;
 442         pi_src += i_src_channels * i_bytes;
 443     }
 444 }
 445
 446 void aout_ChannelExtract( void *p_dst, int i_dst_channels,
 447                           const void *p_src, int i_src_channels,
 448                           int i_sample_count, const int *pi_selection, int i_bits_per_sample )
 449 {
 450     /* It does not work in place */
 451     assert( p_dst != p_src );
 452
 453     /* Force the compiler to inline for the specific cases so it can optimize */
 454     if( i_bits_per_sample == 8 )
 455         ExtractChannel( p_dst, i_dst_channels, p_src, i_src_channels, i_sample_count, pi_selection, 1 );
 456     else  if( i_bits_per_sample == 16 )
 457         ExtractChannel( p_dst, i_dst_channels, p_src, i_src_channels, i_sample_count, pi_selection, 2 );
 458     else  if( i_bits_per_sample == 32 )
 459         ExtractChannel( p_dst, i_dst_channels, p_src, i_src_channels, i_sample_count, pi_selection, 4 );
 460     else  if( i_bits_per_sample == 64 )
 461         ExtractChannel( p_dst, i_dst_channels, p_src, i_src_channels, i_sample_count, pi_selection, 8 );
 462 }
 463
 464 bool aout_CheckChannelExtraction( int *pi_selection,
 465                                   uint32_t *pi_layout, int *pi_channels,
 466                                   const uint32_t pi_order_dst[AOUT_CHAN_MAX],
 467                                   const uint32_t *pi_order_src, int i_channels )
 468 {
 469     static_assert(AOUT_CHAN_MAX <= (sizeof (*pi_order_dst) * CHAR_BIT),
 470                   "Missing bits");
 471
 472     uint32_t i_layout = 0;
 473     int i_out = 0;
 474     int pi_index[AOUT_CHAN_MAX];
 475
 476     /* */
 477     if( !pi_order_dst )
 478         pi_order_dst = pi_vlc_chan_order_wg4;
 479
 480     /* */
 481     for( int i = 0; i < i_channels; i++ )
 482     {
 483         /* Ignore unknown or duplicated channels or not present in output */
 484         if( !pi_order_src[i] || (i_layout & pi_order_src[i]) )
 485             continue;
 486
 487         for( int j = 0; j < AOUT_CHAN_MAX; j++ )
 488         {
 489             if( pi_order_dst[j] == pi_order_src[i] )
 490             {
 491                 assert( i_out < AOUT_CHAN_MAX );
 492                 pi_index[i_out++] = i;
 493                 i_layout |= pi_order_src[i];
 494                 break;
 495             }
 496         }
 497     }
 498
 499     /* */
 500     for( int i = 0, j = 0; i < AOUT_CHAN_MAX; i++ )
 501     {
 502         for( int k = 0; k < i_out; k++ )
 503         {
 504             if( pi_order_dst[i] == pi_order_src[pi_index[k]] )
 505             {
 506                 pi_selection[j++] = pi_index[k];
 507                 break;
 508             }
 509         }
 510     }
 511
 512     *pi_layout = i_layout;
 513     *pi_channels = i_out;
 514
 515     for( int i = 0; i < i_out; i++ )
 516     {
 517         if( pi_selection[i] != i )
 518             return true;
 519     }
 520     return i_out != i_channels;
 521 }
 522
 523 /* Return the order in which filters should be inserted */
 524 static int FilterOrder( const char *psz_name )
 525 {
 526     static const struct {
 527         const char psz_name[10];
 528         int        i_order;
 529     } filter[] = {
 530         { "equalizer",  0 },
 531     };
 532     for( unsigned i = 0; i < ARRAY_SIZE(filter); i++ )
 533     {
 534         if( !strcmp( filter[i].psz_name, psz_name ) )
 535             return filter[i].i_order;
 536     }
 537     return INT_MAX;
 538 }
 539
 540 /* This function will add or remove a module from a string list (colon
 541  * separated). It will return true if there is a modification
 542  * In case p_aout is NULL, we will use configuration instead of variable */
 543 bool aout_ChangeFilterString( vlc_object_t *p_obj, vlc_object_t *p_aout,
 544                               const char *psz_variable,
 545                               const char *psz_name, bool b_add )
 546 {
 547     if( *psz_name == '\0' )
 548         return false;
 549
 550     char *psz_list;
 551     if( p_aout )
 552     {
 553         psz_list = var_GetString( p_aout, psz_variable );
 554     }
 555     else
 556     {
 557         psz_list = var_InheritString( p_obj, psz_variable );
 558     }
 559
 560     /* Split the string into an array of filters */
 561     int i_count = 1;
 562     for( char *p = psz_list; p && *p; p++ )
 563         i_count += *p == ':';
 564     i_count += b_add;
 565
 566     const char **ppsz_filter = calloc( i_count, sizeof(*ppsz_filter) );
 567     if( !ppsz_filter )
 568     {
 569         free( psz_list );
 570         return false;
 571     }
 572     bool b_present = false;
 573     i_count = 0;
 574     for( char *p = psz_list; p && *p; )
 575     {
 576         char *psz_end = strchr(p, ':');
 577         if( psz_end )
 578             *psz_end++ = '\0';
 579         else
 580             psz_end = p + strlen(p);
 581         if( *p )
 582         {
 583             b_present |= !strcmp( p, psz_name );
 584             ppsz_filter[i_count++] = p;
 585         }
 586         p = psz_end;
 587     }
 588     if( b_present == b_add )
 589     {
 590         free( ppsz_filter );
 591         free( psz_list );
 592         return false;
 593     }
 594
 595     if( b_add )
 596     {
 597         int i_order = FilterOrder( psz_name );
 598         int i;
 599         for( i = 0; i < i_count; i++ )
 600         {
 601             if( FilterOrder( ppsz_filter[i] ) > i_order )
 602                 break;
 603         }
 604         if( i < i_count )
 605             memmove( &ppsz_filter[i+1], &ppsz_filter[i], (i_count - i) * sizeof(*ppsz_filter) );
 606         ppsz_filter[i] = psz_name;
 607         i_count++;
 608     }
 609     else
 610     {
 611         for( int i = 0; i < i_count; i++ )
 612         {
 613             if( !strcmp( ppsz_filter[i], psz_name ) )
 614                 ppsz_filter[i] = "";
 615         }
 616     }
 617     size_t i_length = 0;
 618     for( int i = 0; i < i_count; i++ )
 619         i_length += 1 + strlen( ppsz_filter[i] );
 620
 621     char *psz_new = malloc( i_length + 1 );
 622
 623     if( unlikely( !psz_new ) )
 624     {
 625         free( ppsz_filter );
 626         free( psz_list );
 627         return false;
 628     }
 629
 630     *psz_new = '\0';
 631     for( int i = 0; i < i_count; i++ )
 632     {
 633         if( *ppsz_filter[i] == '\0' )
 634             continue;
 635         if( *psz_new )
 636             strcat( psz_new, ":" );
 637         strcat( psz_new, ppsz_filter[i] );
 638     }
 639     free( ppsz_filter );
 640     free( psz_list );
 641
 642     var_SetString( p_obj, psz_variable, psz_new );
 643     if( p_aout )
 644         var_SetString( p_aout, psz_variable, psz_new );
 645     free( psz_new );
 646
 647     return true;
 648 }