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ac3_parser.c
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1 /*
2  * AC-3 parser
3  * Copyright (c) 2003 Fabrice Bellard
4  * Copyright (c) 2003 Michael Niedermayer
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 
24 #include "parser.h"
25 #include "ac3_parser.h"
26 #include "aac_ac3_parser.h"
27 #include "get_bits.h"
28 
29 
30 #define AC3_HEADER_SIZE 7
31 
32 
33 static const uint8_t eac3_blocks[4] = {
34  1, 2, 3, 6
35 };
36 
37 /**
38  * Table for center mix levels
39  * reference: Section 5.4.2.4 cmixlev
40  */
41 static const uint8_t center_levels[4] = { 4, 5, 6, 5 };
42 
43 /**
44  * Table for surround mix levels
45  * reference: Section 5.4.2.5 surmixlev
46  */
47 static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };
48 
49 
51 {
52  int frame_size_code;
53  AC3HeaderInfo *hdr;
54 
55  if (!*phdr)
56  *phdr = av_mallocz(sizeof(AC3HeaderInfo));
57  if (!*phdr)
58  return AVERROR(ENOMEM);
59  hdr = *phdr;
60 
61  memset(hdr, 0, sizeof(*hdr));
62 
63  hdr->sync_word = get_bits(gbc, 16);
64  if(hdr->sync_word != 0x0B77)
66 
67  /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
68  hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F;
69  if(hdr->bitstream_id > 16)
71 
72  hdr->num_blocks = 6;
73 
74  /* set default mix levels */
75  hdr->center_mix_level = 5; // -4.5dB
76  hdr->surround_mix_level = 6; // -6.0dB
77 
78  /* set default dolby surround mode */
80 
81  if(hdr->bitstream_id <= 10) {
82  /* Normal AC-3 */
83  hdr->crc1 = get_bits(gbc, 16);
84  hdr->sr_code = get_bits(gbc, 2);
85  if(hdr->sr_code == 3)
87 
88  frame_size_code = get_bits(gbc, 6);
89  if(frame_size_code > 37)
91 
92  skip_bits(gbc, 5); // skip bsid, already got it
93 
94  hdr->bitstream_mode = get_bits(gbc, 3);
95  hdr->channel_mode = get_bits(gbc, 3);
96 
97  if(hdr->channel_mode == AC3_CHMODE_STEREO) {
98  hdr->dolby_surround_mode = get_bits(gbc, 2);
99  } else {
100  if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)
101  hdr-> center_mix_level = center_levels[get_bits(gbc, 2)];
102  if(hdr->channel_mode & 4)
104  }
105  hdr->lfe_on = get_bits1(gbc);
106 
107  hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
108  hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
109  hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift;
110  hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
111  hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
112  hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT;
113  hdr->substreamid = 0;
114  } else {
115  /* Enhanced AC-3 */
116  hdr->crc1 = 0;
117  hdr->frame_type = get_bits(gbc, 2);
120 
121  hdr->substreamid = get_bits(gbc, 3);
122 
123  hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;
124  if(hdr->frame_size < AC3_HEADER_SIZE)
126 
127  hdr->sr_code = get_bits(gbc, 2);
128  if (hdr->sr_code == 3) {
129  int sr_code2 = get_bits(gbc, 2);
130  if(sr_code2 == 3)
132  hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
133  hdr->sr_shift = 1;
134  } else {
135  hdr->num_blocks = eac3_blocks[get_bits(gbc, 2)];
137  hdr->sr_shift = 0;
138  }
139 
140  hdr->channel_mode = get_bits(gbc, 3);
141  hdr->lfe_on = get_bits1(gbc);
142 
143  hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate /
144  (hdr->num_blocks * 256.0));
145  hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
146  }
148  if (hdr->lfe_on)
150 
151  return 0;
152 }
153 
155 {
156  AC3HeaderInfo tmp, *ptmp = &tmp;
157  int ret = avpriv_ac3_parse_header2(gbc, &ptmp);
158 
159  memcpy(hdr, ptmp, ((intptr_t)&tmp.channel_layout) - ((intptr_t)&tmp) + sizeof(uint64_t));
160  return ret;
161 }
162 
163 static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info,
164  int *need_next_header, int *new_frame_start)
165 {
166  int err;
167  union {
168  uint64_t u64;
169  uint8_t u8[8];
170  } tmp = { av_be2ne64(state) };
171  AC3HeaderInfo hdr, *phdr = &hdr;
172  GetBitContext gbc;
173 
174  init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);
175  err = avpriv_ac3_parse_header2(&gbc, &phdr);
176 
177  if(err < 0)
178  return 0;
179 
180  hdr_info->sample_rate = hdr.sample_rate;
181  hdr_info->bit_rate = hdr.bit_rate;
182  hdr_info->channels = hdr.channels;
183  hdr_info->channel_layout = hdr.channel_layout;
184  hdr_info->samples = hdr.num_blocks * 256;
185  hdr_info->service_type = hdr.bitstream_mode;
186  if (hdr.bitstream_mode == 0x7 && hdr.channels > 1)
188  if(hdr.bitstream_id>10)
189  hdr_info->codec_id = AV_CODEC_ID_EAC3;
190  else if (hdr_info->codec_id == AV_CODEC_ID_NONE)
191  hdr_info->codec_id = AV_CODEC_ID_AC3;
192 
193  *need_next_header = (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
194  *new_frame_start = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
195  return hdr.frame_size;
196 }
197 
199 {
202  s->sync = ac3_sync;
203  return 0;
204 }
205 
206 
209  .priv_data_size = sizeof(AACAC3ParseContext),
210  .parser_init = ac3_parse_init,
211  .parser_parse = ff_aac_ac3_parse,
212  .parser_close = ff_parse_close,
213 };