FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
mpeg4audio.c
Go to the documentation of this file.
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, ret;
86 
87  if (bit_size <= 0)
88  return AVERROR_INVALIDDATA;
89 
90  ret = init_get_bits(&gb, buf, bit_size);
91  if (ret < 0)
92  return ret;
93 
94  c->object_type = get_object_type(&gb);
95  c->sample_rate = get_sample_rate(&gb, &c->sampling_index);
96  c->chan_config = get_bits(&gb, 4);
97  if (c->chan_config < FF_ARRAY_ELEMS(ff_mpeg4audio_channels))
98  c->channels = ff_mpeg4audio_channels[c->chan_config];
99  c->sbr = -1;
100  c->ps = -1;
101  if (c->object_type == AOT_SBR || (c->object_type == AOT_PS &&
102  // check for W6132 Annex YYYY draft MP3onMP4
103  !(show_bits(&gb, 3) & 0x03 && !(show_bits(&gb, 9) & 0x3F)))) {
104  if (c->object_type == AOT_PS)
105  c->ps = 1;
106  c->ext_object_type = AOT_SBR;
107  c->sbr = 1;
108  c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
109  c->object_type = get_object_type(&gb);
110  if (c->object_type == AOT_ER_BSAC)
111  c->ext_chan_config = get_bits(&gb, 4);
112  } else {
113  c->ext_object_type = AOT_NULL;
114  c->ext_sample_rate = 0;
115  }
116  specific_config_bitindex = get_bits_count(&gb);
117 
118  if (c->object_type == AOT_ALS) {
119  skip_bits(&gb, 5);
120  if (show_bits_long(&gb, 24) != MKBETAG('\0','A','L','S'))
121  skip_bits_long(&gb, 24);
122 
123  specific_config_bitindex = get_bits_count(&gb);
124 
125  if (parse_config_ALS(&gb, c))
126  return -1;
127  }
128 
129  if (c->ext_object_type != AOT_SBR && sync_extension) {
130  while (get_bits_left(&gb) > 15) {
131  if (show_bits(&gb, 11) == 0x2b7) { // sync extension
132  get_bits(&gb, 11);
133  c->ext_object_type = get_object_type(&gb);
134  if (c->ext_object_type == AOT_SBR && (c->sbr = get_bits1(&gb)) == 1) {
135  c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
136  if (c->ext_sample_rate == c->sample_rate)
137  c->sbr = -1;
138  }
139  if (get_bits_left(&gb) > 11 && get_bits(&gb, 11) == 0x548)
140  c->ps = get_bits1(&gb);
141  break;
142  } else
143  get_bits1(&gb); // skip 1 bit
144  }
145  }
146 
147  //PS requires SBR
148  if (!c->sbr)
149  c->ps = 0;
150  //Limit implicit PS to the HE-AACv2 Profile
151  if ((c->ps == -1 && c->object_type != AOT_AAC_LC) || c->channels & ~0x01)
152  c->ps = 0;
153 
154  return specific_config_bitindex;
155 }
156 
157 static av_always_inline unsigned int copy_bits(PutBitContext *pb,
158  GetBitContext *gb,
159  int bits)
160 {
161  unsigned int el = get_bits(gb, bits);
162  put_bits(pb, bits, el);
163  return el;
164 }
165 
166 int avpriv_copy_pce_data(PutBitContext *pb, GetBitContext *gb)
167 {
168  int five_bit_ch, four_bit_ch, comment_size, bits;
169  int offset = put_bits_count(pb);
170 
171  copy_bits(pb, gb, 10); //Tag, Object Type, Frequency
172  five_bit_ch = copy_bits(pb, gb, 4); //Front
173  five_bit_ch += copy_bits(pb, gb, 4); //Side
174  five_bit_ch += copy_bits(pb, gb, 4); //Back
175  four_bit_ch = copy_bits(pb, gb, 2); //LFE
176  four_bit_ch += copy_bits(pb, gb, 3); //Data
177  five_bit_ch += copy_bits(pb, gb, 4); //Coupling
178  if (copy_bits(pb, gb, 1)) //Mono Mixdown
179  copy_bits(pb, gb, 4);
180  if (copy_bits(pb, gb, 1)) //Stereo Mixdown
181  copy_bits(pb, gb, 4);
182  if (copy_bits(pb, gb, 1)) //Matrix Mixdown
183  copy_bits(pb, gb, 3);
184  for (bits = five_bit_ch*5+four_bit_ch*4; bits > 16; bits -= 16)
185  copy_bits(pb, gb, 16);
186  if (bits)
187  copy_bits(pb, gb, bits);
188  avpriv_align_put_bits(pb);
189  align_get_bits(gb);
190  comment_size = copy_bits(pb, gb, 8);
191  for (; comment_size > 0; comment_size--)
192  copy_bits(pb, gb, 8);
193 
194  return put_bits_count(pb) - offset;
195 }
Generated on Sun Mar 8 2015 02:34:56 for FFmpeg by   doxygen 1.8.2