modules/codec/a52.h

   1 /*****************************************************************************
   2  * a52.h
   3  *****************************************************************************
   4  * Copyright (C) 2001-2009 Laurent Aimar
   5  * $Id$
   6  *
   7  * Authors: Stéphane Borel <stef@via.ecp.fr>
   8  *          Christophe Massiot <massiot@via.ecp.fr>
   9  *          Gildas Bazin <gbazin@videolan.org>
  10  *          Laurent Aimar <fenrir@via.ecp.fr>
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  25  *****************************************************************************/
  26
  27 #ifndef _VLC_A52_H
  28 #define _VLC_A52_H 1
  29
  30 #include <vlc_aout.h>
  31 #include <vlc_bits.h>
  32
  33 typedef struct
  34 {
  35     unsigned int i_count;
  36     unsigned int i_configuration;
  37 } vlc_a52_acmod_t;
  38
  39 /**
  40  * Minimum AC3 header size that vlc_a52_header_Parse needs.
  41  */
  42 #define VLC_A52_HEADER_SIZE (8)
  43
  44 /**
  45  * AC3 header information.
  46  */
  47 typedef struct
  48 {
  49     bool b_eac3;
  50
  51     unsigned int i_channels;
  52     unsigned int i_channels_conf;
  53     unsigned int i_rate;
  54     unsigned int i_bitrate;
  55
  56     unsigned int i_size;
  57     unsigned int i_samples;
  58
  59 } vlc_a52_header_t;
  60
  61 /**
  62  * It parse AC3 sync info.
  63  *
  64  * This code is borrowed from liba52 by Aaron Holtzman & Michel Lespinasse,
  65  * since we don't want to oblige S/PDIF people to use liba52 just to get
  66  * their SyncInfo...
  67  */
  68 static inline int vlc_a52_header_ParseAc3( vlc_a52_header_t *p_header,
  69                                            const uint8_t *p_buf,
  70                                            const vlc_a52_acmod_t *p_acmod )
  71 {
  72     static const uint8_t pi_halfrate[12] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3 };
  73     static const unsigned int pi_bitrate[] = { 32,  40,  48,  56,  64,  80,  96, 112,
  74                                 128, 160, 192, 224, 256, 320, 384, 448,
  75                                 512, 576, 640 };
  76     static const uint8_t pi_lfeon[8] = { 0x10, 0x10, 0x04, 0x04,
  77                                       0x04, 0x01, 0x04, 0x01 };
  78
  79     /* */
  80     const unsigned i_rate_shift = pi_halfrate[p_buf[5] >> 3];
  81
  82     /* acmod, dsurmod and lfeon */
  83     const unsigned i_acmod = p_buf[6] >> 5;
  84     if( (p_buf[6] & 0xf8) == 0x50 )
  85     {
  86         /* Dolby surround = stereo + Dolby */
  87         p_header->i_channels = 2;
  88         p_header->i_channels_conf = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
  89                             | AOUT_CHAN_DOLBYSTEREO;
  90     }
  91     else
  92     {
  93         p_header->i_channels      = p_acmod[i_acmod].i_count;
  94         p_header->i_channels_conf = p_acmod[i_acmod].i_configuration;
  95     }
  96
  97     if( p_buf[6] & pi_lfeon[i_acmod] )
  98     {
  99         p_header->i_channels++;
 100         p_header->i_channels_conf |= AOUT_CHAN_LFE;
 101     }
 102
 103     const unsigned i_frmsizecod = p_buf[4] & 63;
 104     if( i_frmsizecod >= 38 )
 105         return VLC_EGENERIC;
 106     const unsigned i_bitrate_base = pi_bitrate[i_frmsizecod >> 1];
 107     p_header->i_bitrate = (i_bitrate_base * 1000) >> i_rate_shift;
 108
 109     switch( p_buf[4] & 0xc0 )
 110     {
 111     case 0:
 112         p_header->i_rate = 48000 >> i_rate_shift;
 113         p_header->i_size = 4 * i_bitrate_base;
 114         break;
 115     case 0x40:
 116         p_header->i_rate = 44100 >> i_rate_shift;
 117         p_header->i_size = 2 * (320 * i_bitrate_base / 147 + (i_frmsizecod & 1));
 118         break;
 119     case 0x80:
 120         p_header->i_rate = 32000 >> i_rate_shift;
 121         p_header->i_size = 6 * i_bitrate_base;
 122         break;
 123     default:
 124         return VLC_EGENERIC;
 125     }
 126     p_header->i_samples = 6*256;
 127
 128     p_header->b_eac3 = false;
 129     return VLC_SUCCESS;
 130 }
 131
 132 /**
 133  * It parse E-AC3 sync info
 134  */
 135 static inline int vlc_a52_header_ParseEac3( vlc_a52_header_t *p_header,
 136                                             const uint8_t *p_buf,
 137                                             const vlc_a52_acmod_t *p_acmod )
 138 {
 139     static const unsigned pi_samplerate[3] = { 48000, 44100, 32000 };
 140     unsigned i_numblkscod;
 141     bs_t s;
 142
 143
 144     bs_init( &s, (void*)p_buf, VLC_A52_HEADER_SIZE );
 145     bs_skip( &s, 16 +   /* start code */
 146                  2 +    /* stream type */
 147                  3 );   /* substream id */
 148     const unsigned i_frame_size = bs_read( &s, 11 );
 149     if( i_frame_size < 2 )
 150         return VLC_EGENERIC;
 151     p_header->i_size = 2 * ( i_frame_size + 1 );
 152
 153     const unsigned i_fscod = bs_read( &s, 2 );
 154     if( i_fscod == 0x03 )
 155     {
 156         const unsigned i_fscod2 = bs_read( &s, 2 );
 157         if( i_fscod2 == 0X03 )
 158             return VLC_EGENERIC;
 159         p_header->i_rate = pi_samplerate[i_fscod2] / 2;
 160         i_numblkscod = 6;
 161     }
 162     else
 163     {
 164         static const int pi_blocks[4] = { 1, 2, 3, 6 };
 165
 166         p_header->i_rate = pi_samplerate[i_fscod];
 167         i_numblkscod = pi_blocks[bs_read( &s, 2 )];
 168     }
 169
 170     const unsigned i_acmod = bs_read( &s, 3 );
 171     const unsigned i_lfeon = bs_read1( &s );
 172
 173     p_header->i_channels      = p_acmod[i_acmod].i_count + i_lfeon;
 174     p_header->i_channels_conf = p_acmod[i_acmod].i_configuration | ( i_lfeon ? AOUT_CHAN_LFE : 0);
 175     p_header->i_bitrate = 8 * p_header->i_size * (p_header->i_rate) / (i_numblkscod * 256);
 176     p_header->i_samples = i_numblkscod * 256;
 177
 178     p_header->b_eac3 = true;
 179     return VLC_SUCCESS;
 180 }
 181
 182 /**
 183  * It will parse the header AC3 frame and fill vlc_a52_header_t* if
 184  * it is valid or return VLC_EGENERIC.
 185  *
 186  * XXX It will only recognize big endian bitstream ie starting with 0x0b, 0x77
 187  */
 188 static inline int vlc_a52_header_Parse( vlc_a52_header_t *p_header,
 189                                         const uint8_t *p_buffer, int i_buffer )
 190 {
 191     static const vlc_a52_acmod_t p_acmod[8] = {
 192         { 2, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_DUALMONO },   /* Dual-channel 1+1 */
 193         { 1, AOUT_CHAN_CENTER },                                        /* Mono 1/0 */
 194         { 2, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT },                        /* Stereo 2/0 */
 195         { 3, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER },     /* 3F 3/0 */
 196         { 3, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_REARCENTER }, /* 2F1R 2/1 */
 197         { 4, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER |
 198              AOUT_CHAN_REARCENTER },                                    /* 3F1R 3/1 */
 199         { 4, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT |
 200              AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT },                /* 2F2R 2/2 */
 201         { 5, AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER |
 202              AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT },                /* 3F2R 3/2 */
 203     };
 204
 205     if( i_buffer < VLC_A52_HEADER_SIZE )
 206         return VLC_EGENERIC;
 207
 208     /* Check synword */
 209     if( p_buffer[0] != 0x0b || p_buffer[1] != 0x77 )
 210         return VLC_EGENERIC;
 211
 212     /* Check bsid */
 213     const int bsid = p_buffer[5] >> 3;
 214     if( bsid > 16 )
 215         return VLC_EGENERIC;
 216
 217     if( bsid <= 10 )
 218     {
 219         if( vlc_a52_header_ParseAc3( p_header, p_buffer, p_acmod ) )
 220             return VLC_EGENERIC;
 221     }
 222     else
 223     {
 224         if( vlc_a52_header_ParseEac3( p_header, p_buffer, p_acmod ) )
 225             return VLC_EGENERIC;
 226     }
 227     return VLC_SUCCESS;
 228 }
 229
 230 #endif
 231