mpeg4audio.c
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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 Libav.
7  *
8  * Libav 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  * Libav 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 Libav; 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 
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 
56  96000, 88200, 64000, 48000, 44100, 32000,
57  24000, 22050, 16000, 12000, 11025, 8000, 7350
58 };
59 
60 const uint8_t ff_mpeg4audio_channels[8] = {
61  0, 1, 2, 3, 4, 5, 6, 8
62 };
63 
64 static inline int get_object_type(GetBitContext *gb)
65 {
66  int object_type = get_bits(gb, 5);
67  if (object_type == AOT_ESCAPE)
68  object_type = 32 + get_bits(gb, 6);
69  return object_type;
70 }
71 
72 static inline int get_sample_rate(GetBitContext *gb, int *index)
73 {
74  *index = get_bits(gb, 4);
75  return *index == 0x0f ? get_bits(gb, 24) :
77 }
78 
80  int bit_size, int sync_extension)
81 {
82  GetBitContext gb;
83  int specific_config_bitindex;
84 
85  init_get_bits(&gb, buf, bit_size);
86  c->object_type = get_object_type(&gb);
88  c->chan_config = get_bits(&gb, 4);
91  c->sbr = -1;
92  c->ps = -1;
93  if (c->object_type == AOT_SBR || (c->object_type == AOT_PS &&
94  // check for W6132 Annex YYYY draft MP3onMP4
95  !(show_bits(&gb, 3) & 0x03 && !(show_bits(&gb, 9) & 0x3F)))) {
96  if (c->object_type == AOT_PS)
97  c->ps = 1;
99  c->sbr = 1;
101  c->object_type = get_object_type(&gb);
102  if (c->object_type == AOT_ER_BSAC)
103  c->ext_chan_config = get_bits(&gb, 4);
104  } else {
106  c->ext_sample_rate = 0;
107  }
108  specific_config_bitindex = get_bits_count(&gb);
109 
110  if (c->object_type == AOT_ALS) {
111  skip_bits(&gb, 5);
112  if (show_bits_long(&gb, 24) != MKBETAG('\0','A','L','S'))
113  skip_bits_long(&gb, 24);
114 
115  specific_config_bitindex = get_bits_count(&gb);
116 
117  if (parse_config_ALS(&gb, c))
118  return -1;
119  }
120 
121  if (c->ext_object_type != AOT_SBR && sync_extension) {
122  while (get_bits_left(&gb) > 15) {
123  if (show_bits(&gb, 11) == 0x2b7) { // sync extension
124  get_bits(&gb, 11);
126  if (c->ext_object_type == AOT_SBR && (c->sbr = get_bits1(&gb)) == 1)
128  if (get_bits_left(&gb) > 11 && get_bits(&gb, 11) == 0x548)
129  c->ps = get_bits1(&gb);
130  break;
131  } else
132  get_bits1(&gb); // skip 1 bit
133  }
134  }
135 
136  //PS requires SBR
137  if (!c->sbr)
138  c->ps = 0;
139  //Limit implicit PS to the HE-AACv2 Profile
140  if ((c->ps == -1 && c->object_type != AOT_AAC_LC) || c->channels & ~0x01)
141  c->ps = 0;
142 
143  return specific_config_bitindex;
144 }
145 
146 static av_always_inline unsigned int copy_bits(PutBitContext *pb,
147  GetBitContext *gb,
148  int bits)
149 {
150  unsigned int el = get_bits(gb, bits);
151  put_bits(pb, bits, el);
152  return el;
153 }
154 
156 {
157  int five_bit_ch, four_bit_ch, comment_size, bits;
158  int offset = put_bits_count(pb);
159 
160  copy_bits(pb, gb, 10); //Tag, Object Type, Frequency
161  five_bit_ch = copy_bits(pb, gb, 4); //Front
162  five_bit_ch += copy_bits(pb, gb, 4); //Side
163  five_bit_ch += copy_bits(pb, gb, 4); //Back
164  four_bit_ch = copy_bits(pb, gb, 2); //LFE
165  four_bit_ch += copy_bits(pb, gb, 3); //Data
166  five_bit_ch += copy_bits(pb, gb, 4); //Coupling
167  if (copy_bits(pb, gb, 1)) //Mono Mixdown
168  copy_bits(pb, gb, 4);
169  if (copy_bits(pb, gb, 1)) //Stereo Mixdown
170  copy_bits(pb, gb, 4);
171  if (copy_bits(pb, gb, 1)) //Matrix Mixdown
172  copy_bits(pb, gb, 3);
173  for (bits = five_bit_ch*5+four_bit_ch*4; bits > 16; bits -= 16)
174  copy_bits(pb, gb, 16);
175  if (bits)
176  copy_bits(pb, gb, bits);
178  align_get_bits(gb);
179  comment_size = copy_bits(pb, gb, 8);
180  for (; comment_size > 0; comment_size--)
181  copy_bits(pb, gb, 8);
182 
183  return put_bits_count(pb) - offset;
184 }