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  1. /*
  2.  * MPEG-4 Audio common code
  3.  * Copyright (c) 2008 Baptiste Coudurier <baptiste.coudurier@free.fr>
  4.  * Copyright (c) 2009 Alex Converse <alex.converse@gmail.com>
  5.  *
  6.  * This file is part of FFmpeg.
  7.  *
  8.  * FFmpeg is free software; you can redistribute it and/or
  9.  * modify it under the terms of the GNU Lesser General Public
  10.  * License as published by the Free Software Foundation; either
  11.  * version 2.1 of the License, or (at your option) any later version.
  12.  *
  13.  * FFmpeg 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 GNU
  16.  * Lesser General Public License for more details.
  17.  *
  18.  * You should have received a copy of the GNU Lesser General Public
  19.  * License along with FFmpeg; if not, write to the Free Software
  20.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21.  */
  22.  
  23. #include "get_bits.h"
  24. #include "put_bits.h"
  25. #include "mpeg4audio.h"
  26.  
  27. /**
  28.  * Parse MPEG-4 audio configuration for ALS object type.
  29.  * @param[in] gb       bit reader context
  30.  * @param[in] c        MPEG4AudioConfig structure to fill
  31.  * @return on success 0 is returned, otherwise a value < 0
  32.  */
  33. static int parse_config_ALS(GetBitContext *gb, MPEG4AudioConfig *c)
  34. {
  35.     if (get_bits_left(gb) < 112)
  36.         return -1;
  37.  
  38.     if (get_bits_long(gb, 32) != MKBETAG('A','L','S','\0'))
  39.         return -1;
  40.  
  41.     // override AudioSpecificConfig channel configuration and sample rate
  42.     // which are buggy in old ALS conformance files
  43.     c->sample_rate = get_bits_long(gb, 32);
  44.  
  45.     // skip number of samples
  46.     skip_bits_long(gb, 32);
  47.  
  48.     // read number of channels
  49.     c->chan_config = 0;
  50.     c->channels    = get_bits(gb, 16) + 1;
  51.  
  52.     return 0;
  53. }
  54.  
  55. /* XXX: make sure to update the copies in the different encoders if you change
  56.  * this table */
  57. const int avpriv_mpeg4audio_sample_rates[16] = {
  58.     96000, 88200, 64000, 48000, 44100, 32000,
  59.     24000, 22050, 16000, 12000, 11025, 8000, 7350
  60. };
  61.  
  62. const uint8_t ff_mpeg4audio_channels[8] = {
  63.     0, 1, 2, 3, 4, 5, 6, 8
  64. };
  65.  
  66. static inline int get_object_type(GetBitContext *gb)
  67. {
  68.     int object_type = get_bits(gb, 5);
  69.     if (object_type == AOT_ESCAPE)
  70.         object_type = 32 + get_bits(gb, 6);
  71.     return object_type;
  72. }
  73.  
  74. static inline int get_sample_rate(GetBitContext *gb, int *index)
  75. {
  76.     *index = get_bits(gb, 4);
  77.     return *index == 0x0f ? get_bits(gb, 24) :
  78.         avpriv_mpeg4audio_sample_rates[*index];
  79. }
  80.  
  81. int avpriv_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf,
  82.                                  int bit_size, int sync_extension)
  83. {
  84.     GetBitContext gb;
  85.     int specific_config_bitindex;
  86.  
  87.     if (bit_size <= 0 || init_get_bits(&gb, buf, bit_size) < 0)
  88.         return AVERROR_INVALIDDATA;
  89.     c->object_type = get_object_type(&gb);
  90.     c->sample_rate = get_sample_rate(&gb, &c->sampling_index);
  91.     c->chan_config = get_bits(&gb, 4);
  92.     if (c->chan_config < FF_ARRAY_ELEMS(ff_mpeg4audio_channels))
  93.         c->channels = ff_mpeg4audio_channels[c->chan_config];
  94.     c->sbr = -1;
  95.     c->ps  = -1;
  96.     if (c->object_type == AOT_SBR || (c->object_type == AOT_PS &&
  97.         // check for W6132 Annex YYYY draft MP3onMP4
  98.         !(show_bits(&gb, 3) & 0x03 && !(show_bits(&gb, 9) & 0x3F)))) {
  99.         if (c->object_type == AOT_PS)
  100.             c->ps = 1;
  101.         c->ext_object_type = AOT_SBR;
  102.         c->sbr = 1;
  103.         c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
  104.         c->object_type = get_object_type(&gb);
  105.         if (c->object_type == AOT_ER_BSAC)
  106.             c->ext_chan_config = get_bits(&gb, 4);
  107.     } else {
  108.         c->ext_object_type = AOT_NULL;
  109.         c->ext_sample_rate = 0;
  110.     }
  111.     specific_config_bitindex = get_bits_count(&gb);
  112.  
  113.     if (c->object_type == AOT_ALS) {
  114.         skip_bits(&gb, 5);
  115.         if (show_bits_long(&gb, 24) != MKBETAG('\0','A','L','S'))
  116.             skip_bits_long(&gb, 24);
  117.  
  118.         specific_config_bitindex = get_bits_count(&gb);
  119.  
  120.         if (parse_config_ALS(&gb, c))
  121.             return -1;
  122.     }
  123.  
  124.     if (c->ext_object_type != AOT_SBR && sync_extension) {
  125.         while (get_bits_left(&gb) > 15) {
  126.             if (show_bits(&gb, 11) == 0x2b7) { // sync extension
  127.                 get_bits(&gb, 11);
  128.                 c->ext_object_type = get_object_type(&gb);
  129.                 if (c->ext_object_type == AOT_SBR && (c->sbr = get_bits1(&gb)) == 1) {
  130.                     c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
  131.                     if (c->ext_sample_rate == c->sample_rate)
  132.                         c->sbr = -1;
  133.                 }
  134.                 if (get_bits_left(&gb) > 11 && get_bits(&gb, 11) == 0x548)
  135.                     c->ps = get_bits1(&gb);
  136.                 break;
  137.             } else
  138.                 get_bits1(&gb); // skip 1 bit
  139.         }
  140.     }
  141.  
  142.     //PS requires SBR
  143.     if (!c->sbr)
  144.         c->ps = 0;
  145.     //Limit implicit PS to the HE-AACv2 Profile
  146.     if ((c->ps == -1 && c->object_type != AOT_AAC_LC) || c->channels & ~0x01)
  147.         c->ps = 0;
  148.  
  149.     return specific_config_bitindex;
  150. }
  151.  
  152. static av_always_inline unsigned int copy_bits(PutBitContext *pb,
  153.                                                GetBitContext *gb,
  154.                                                int bits)
  155. {
  156.     unsigned int el = get_bits(gb, bits);
  157.     put_bits(pb, bits, el);
  158.     return el;
  159. }
  160.  
  161. int avpriv_copy_pce_data(PutBitContext *pb, GetBitContext *gb)
  162. {
  163.     int five_bit_ch, four_bit_ch, comment_size, bits;
  164.     int offset = put_bits_count(pb);
  165.  
  166.     copy_bits(pb, gb, 10);                  //Tag, Object Type, Frequency
  167.     five_bit_ch  = copy_bits(pb, gb, 4);    //Front
  168.     five_bit_ch += copy_bits(pb, gb, 4);    //Side
  169.     five_bit_ch += copy_bits(pb, gb, 4);    //Back
  170.     four_bit_ch  = copy_bits(pb, gb, 2);    //LFE
  171.     four_bit_ch += copy_bits(pb, gb, 3);    //Data
  172.     five_bit_ch += copy_bits(pb, gb, 4);    //Coupling
  173.     if (copy_bits(pb, gb, 1))               //Mono Mixdown
  174.         copy_bits(pb, gb, 4);
  175.     if (copy_bits(pb, gb, 1))               //Stereo Mixdown
  176.         copy_bits(pb, gb, 4);
  177.     if (copy_bits(pb, gb, 1))               //Matrix Mixdown
  178.         copy_bits(pb, gb, 3);
  179.     for (bits = five_bit_ch*5+four_bit_ch*4; bits > 16; bits -= 16)
  180.         copy_bits(pb, gb, 16);
  181.     if (bits)
  182.         copy_bits(pb, gb, bits);
  183.     avpriv_align_put_bits(pb);
  184.     align_get_bits(gb);
  185.     comment_size = copy_bits(pb, gb, 8);
  186.     for (; comment_size > 0; comment_size--)
  187.         copy_bits(pb, gb, 8);
  188.  
  189.     return put_bits_count(pb) - offset;
  190. }
  191.