FFmpeg
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 
23 #include "config_components.h"
24 
26 #include "libavutil/mem.h"
27 #include "parser.h"
28 #include "ac3defs.h"
29 #include "ac3tab.h"
30 #include "ac3_parser.h"
31 #include "ac3_parser_internal.h"
32 #include "aac_ac3_parser.h"
33 #include "get_bits.h"
34 
35 
36 #define AC3_HEADER_SIZE 7
37 
38 #if CONFIG_AC3_PARSER
39 
40 static const uint8_t eac3_blocks[4] = {
41  1, 2, 3, 6
42 };
43 
44 /**
45  * Table for center mix levels
46  * reference: Section 5.4.2.4 cmixlev
47  */
48 static const uint8_t center_levels[4] = { 4, 5, 6, 5 };
49 
50 /**
51  * Table for surround mix levels
52  * reference: Section 5.4.2.5 surmixlev
53  */
54 static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };
55 
56 int ff_ac3_find_syncword(const uint8_t *buf, int buf_size)
57 {
58  int i;
59 
60  for (i = 1; i < buf_size; i += 2) {
61  if (buf[i] == 0x77 || buf[i] == 0x0B) {
62  if ((buf[i] ^ buf[i-1]) == (0x77 ^ 0x0B)) {
63  i--;
64  break;
65  } else if ((buf[i] ^ buf[i+1]) == (0x77 ^ 0x0B)) {
66  break;
67  }
68  }
69  }
70  if (i >= buf_size)
71  return AVERROR_INVALIDDATA;
72 
73  return i;
74 }
75 
77 {
78  int frame_size_code;
79 
80  memset(hdr, 0, sizeof(*hdr));
81 
82  hdr->sync_word = get_bits(gbc, 16);
83  if(hdr->sync_word != 0x0B77)
84  return AC3_PARSE_ERROR_SYNC;
85 
86  /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
87  hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F;
88  if(hdr->bitstream_id > 16)
89  return AC3_PARSE_ERROR_BSID;
90 
91  hdr->num_blocks = 6;
92  hdr->ac3_bit_rate_code = -1;
93 
94  /* set default mix levels */
95  hdr->center_mix_level = 5; // -4.5dB
96  hdr->surround_mix_level = 6; // -6.0dB
97 
98  /* set default dolby surround mode */
100 
101  if(hdr->bitstream_id <= 10) {
102  /* Normal AC-3 */
103  hdr->crc1 = get_bits(gbc, 16);
104  hdr->sr_code = get_bits(gbc, 2);
105  if(hdr->sr_code == 3)
107 
108  frame_size_code = get_bits(gbc, 6);
109  if(frame_size_code > 37)
111 
112  hdr->ac3_bit_rate_code = (frame_size_code >> 1);
113 
114  skip_bits(gbc, 5); // skip bsid, already got it
115 
116  hdr->bitstream_mode = get_bits(gbc, 3);
117  hdr->channel_mode = get_bits(gbc, 3);
118 
119  if(hdr->channel_mode == AC3_CHMODE_STEREO) {
120  hdr->dolby_surround_mode = get_bits(gbc, 2);
121  } else {
122  if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)
123  hdr-> center_mix_level = center_levels[get_bits(gbc, 2)];
124  if(hdr->channel_mode & 4)
125  hdr->surround_mix_level = surround_levels[get_bits(gbc, 2)];
126  }
127  hdr->lfe_on = get_bits1(gbc);
128 
129  hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
130  hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
131  hdr->bit_rate = (ff_ac3_bitrate_tab[hdr->ac3_bit_rate_code] * 1000) >> hdr->sr_shift;
132  hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
133  hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
134  hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT;
135  hdr->substreamid = 0;
136  } else {
137  /* Enhanced AC-3 */
138  hdr->crc1 = 0;
139  hdr->frame_type = get_bits(gbc, 2);
142 
143  hdr->substreamid = get_bits(gbc, 3);
144 
145  hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;
146  if(hdr->frame_size < AC3_HEADER_SIZE)
148 
149  hdr->sr_code = get_bits(gbc, 2);
150  if (hdr->sr_code == 3) {
151  int sr_code2 = get_bits(gbc, 2);
152  if(sr_code2 == 3)
154  hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
155  hdr->sr_shift = 1;
156  } else {
157  hdr->num_blocks = eac3_blocks[get_bits(gbc, 2)];
159  hdr->sr_shift = 0;
160  }
161 
162  hdr->channel_mode = get_bits(gbc, 3);
163  hdr->lfe_on = get_bits1(gbc);
164 
165  hdr->bit_rate = 8LL * hdr->frame_size * hdr->sample_rate /
166  (hdr->num_blocks * 256);
167  hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
168  }
170  if (hdr->lfe_on)
172 
173  return 0;
174 }
175 
176 // TODO: Better way to pass AC3HeaderInfo fields to mov muxer.
177 int avpriv_ac3_parse_header(AC3HeaderInfo **phdr, const uint8_t *buf,
178  size_t size)
179 {
180  GetBitContext gb;
181  AC3HeaderInfo *hdr;
182  int err;
183 
184  if (!*phdr)
185  *phdr = av_mallocz(sizeof(AC3HeaderInfo));
186  if (!*phdr)
187  return AVERROR(ENOMEM);
188  hdr = *phdr;
189 
190  err = init_get_bits8(&gb, buf, size);
191  if (err < 0)
192  return AVERROR_INVALIDDATA;
193  err = ff_ac3_parse_header(&gb, hdr);
194  if (err < 0)
195  return AVERROR_INVALIDDATA;
196 
197  return get_bits_count(&gb);
198 }
199 
200 int av_ac3_parse_header(const uint8_t *buf, size_t size,
201  uint8_t *bitstream_id, uint16_t *frame_size)
202 {
203  GetBitContext gb;
204  AC3HeaderInfo hdr;
205  int err;
206 
207  err = init_get_bits8(&gb, buf, size);
208  if (err < 0)
209  return AVERROR_INVALIDDATA;
210  err = ff_ac3_parse_header(&gb, &hdr);
211  if (err < 0)
212  return AVERROR_INVALIDDATA;
213 
214  *bitstream_id = hdr.bitstream_id;
215  *frame_size = hdr.frame_size;
216 
217  return 0;
218 }
219 
220 static int ac3_sync(uint64_t state, int *need_next_header, int *new_frame_start)
221 {
222  int err;
223  union {
224  uint64_t u64;
225  uint8_t u8[8 + AV_INPUT_BUFFER_PADDING_SIZE];
226  } tmp = { av_be2ne64(state) };
227  AC3HeaderInfo hdr;
228  GetBitContext gbc;
229 
230  if (tmp.u8[1] == 0x77 && tmp.u8[2] == 0x0b) {
231  FFSWAP(uint8_t, tmp.u8[1], tmp.u8[2]);
232  FFSWAP(uint8_t, tmp.u8[3], tmp.u8[4]);
233  FFSWAP(uint8_t, tmp.u8[5], tmp.u8[6]);
234  }
235 
236  init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);
237  err = ff_ac3_parse_header(&gbc, &hdr);
238 
239  if(err < 0)
240  return 0;
241 
242  *new_frame_start = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
243  *need_next_header = *new_frame_start || (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
244  return hdr.frame_size;
245 }
246 
247 static av_cold int ac3_parse_init(AVCodecParserContext *s1)
248 {
250  s->header_size = AC3_HEADER_SIZE;
251  s->crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
252  s->sync = ac3_sync;
253  return 0;
254 }
255 
256 
259  .priv_data_size = sizeof(AACAC3ParseContext),
260  .parser_init = ac3_parse_init,
261  .parser_parse = ff_aac_ac3_parse,
262  .parser_close = ff_parse_close,
263 };
264 
265 #else
266 
267 int avpriv_ac3_parse_header(AC3HeaderInfo **phdr, const uint8_t *buf,
268  size_t size)
269 {
270  return AVERROR(ENOSYS);
271 }
272 
273 int av_ac3_parse_header(const uint8_t *buf, size_t size,
274  uint8_t *bitstream_id, uint16_t *frame_size)
275 {
276  return AVERROR(ENOSYS);
277 }
278 #endif
AC3HeaderInfo::center_mix_level
int center_mix_level
Center mix level index.
Definition: ac3_parser_internal.h:47
AV_CODEC_ID_AC3
@ AV_CODEC_ID_AC3
Definition: codec_id.h:443
AC3HeaderInfo::frame_type
uint8_t frame_type
Definition: ac3_parser_internal.h:45
AC3HeaderInfo::dolby_surround_mode
int dolby_surround_mode
Definition: ac3_parser_internal.h:51
show_bits_long
static unsigned int show_bits_long(GetBitContext *s, int n)
Show 0-32 bits.
Definition: get_bits.h:495
AC3_HEADER_SIZE
#define AC3_HEADER_SIZE
Definition: ac3_parser.c:36
ff_ac3_channel_layout_tab
const uint16_t ff_ac3_channel_layout_tab[8]
Map audio coding mode (acmod) to channel layout mask.
Definition: ac3_channel_layout_tab.h:31
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
get_bits_count
static int get_bits_count(const GetBitContext *s)
Definition: get_bits.h:266
aac_ac3_parser.h
av_be2ne64
#define av_be2ne64(x)
Definition: bswap.h:90
tmp
static uint8_t tmp[11]
Definition: aes_ctr.c:28
ff_parse_close
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:289
ff_ac3_channels_tab
const uint8_t ff_ac3_channels_tab[8]
Map audio coding mode (acmod) to number of full-bandwidth channels.
Definition: ac3tab.c:80
FFMAX
#define FFMAX(a, b)
Definition: macros.h:47
ac3_parser.h
EAC3_FRAME_TYPE_RESERVED
@ EAC3_FRAME_TYPE_RESERVED
Definition: ac3defs.h:101
init_get_bits
static int init_get_bits(GetBitContext *s, const uint8_t *buffer, int bit_size)
Initialize GetBitContext.
Definition: get_bits.h:514
av_ac3_parse_header
int av_ac3_parse_header(const uint8_t *buf, size_t size, uint8_t *bitstream_id, uint16_t *frame_size)
Extract the bitstream ID and the frame size from AC-3 data.
Definition: ac3_parser.c:273
skip_bits
static void skip_bits(GetBitContext *s, int n)
Definition: get_bits.h:381
AC3_PARSE_ERROR_FRAME_TYPE
@ AC3_PARSE_ERROR_FRAME_TYPE
Definition: ac3_parser_internal.h:72
get_bits
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:335
AC3HeaderInfo::channel_layout
uint64_t channel_layout
Definition: ac3_parser_internal.h:62
GetBitContext
Definition: get_bits.h:108
AC3HeaderInfo
Definition: ac3_parser_internal.h:34
AC3HeaderInfo::frame_size
uint16_t frame_size
Definition: ac3_parser_internal.h:61
EAC3_FRAME_TYPE_DEPENDENT
@ EAC3_FRAME_TYPE_DEPENDENT
Definition: ac3defs.h:99
AC3HeaderInfo::channel_mode
uint8_t channel_mode
Definition: ac3_parser_internal.h:43
av_cold
#define av_cold
Definition: attributes.h:90
init_get_bits8
static int init_get_bits8(GetBitContext *s, const uint8_t *buffer, int byte_size)
Initialize GetBitContext.
Definition: get_bits.h:545
AC3HeaderInfo::sync_word
uint16_t sync_word
Definition: ac3_parser_internal.h:38
AV_CH_LOW_FREQUENCY
#define AV_CH_LOW_FREQUENCY
Definition: channel_layout.h:175
s
#define s(width, name)
Definition: cbs_vp9.c:198
frame_size
int frame_size
Definition: mxfenc.c:2424
AC3_PARSE_ERROR_SYNC
@ AC3_PARSE_ERROR_SYNC
Definition: ac3_parser_internal.h:68
AC3HeaderInfo::crc1
uint16_t crc1
Definition: ac3_parser_internal.h:39
get_bits.h
AC3HeaderInfo::sample_rate
uint16_t sample_rate
Definition: ac3_parser_internal.h:58
AV_CRC_16_ANSI
@ AV_CRC_16_ANSI
Definition: crc.h:50
ff_aac_ac3_parse
int ff_aac_ac3_parse(AVCodecParserContext *s1, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
Definition: aac_ac3_parser.c:32
ac3defs.h
ff_ac3_parser
const AVCodecParser ff_ac3_parser
get_bits1
static unsigned int get_bits1(GetBitContext *s)
Definition: get_bits.h:388
AC3HeaderInfo::substreamid
int substreamid
substream identification
Definition: ac3_parser_internal.h:46
AACAC3ParseContext
Definition: aac_ac3_parser.h:31
state
static struct @435 state
AC3HeaderInfo::num_blocks
int num_blocks
number of audio blocks
Definition: ac3_parser_internal.h:50
AC3_DSURMOD_NOTINDICATED
@ AC3_DSURMOD_NOTINDICATED
Definition: ac3defs.h:67
AV_CODEC_ID_EAC3
@ AV_CODEC_ID_EAC3
Definition: codec_id.h:480
EAC3_FRAME_TYPE_AC3_CONVERT
@ EAC3_FRAME_TYPE_AC3_CONVERT
Definition: ac3defs.h:100
AC3HeaderInfo::channels
uint8_t channels
Definition: ac3_parser_internal.h:60
ac3_parser_internal.h
AC3_CHMODE_STEREO
@ AC3_CHMODE_STEREO
Definition: ac3defs.h:57
AVCodecParser::codec_ids
int codec_ids[7]
Definition: avcodec.h:2868
AC3HeaderInfo::lfe_on
uint8_t lfe_on
Definition: ac3_parser_internal.h:44
size
int size
Definition: twinvq_data.h:10344
av_crc_get_table
const AVCRC * av_crc_get_table(AVCRCId crc_id)
Get an initialized standard CRC table.
Definition: crc.c:374
AC3HeaderInfo::bitstream_mode
uint8_t bitstream_mode
Definition: ac3_parser_internal.h:42
AC3HeaderInfo::ac3_bit_rate_code
int8_t ac3_bit_rate_code
Definition: ac3_parser_internal.h:63
ff_ac3_sample_rate_tab
const int ff_ac3_sample_rate_tab[]
Definition: ac3tab.c:95
AC3_PARSE_ERROR_BSID
@ AC3_PARSE_ERROR_BSID
Definition: ac3_parser_internal.h:69
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:256
avpriv_ac3_parse_header
int avpriv_ac3_parse_header(AC3HeaderInfo **phdr, const uint8_t *buf, size_t size)
Definition: ac3_parser.c:267
ff_ac3_find_syncword
int ff_ac3_find_syncword(const uint8_t *buf, int buf_size)
av_mallocz
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:256
parser.h
ff_ac3_frame_size_tab
const uint16_t ff_ac3_frame_size_tab[38][3]
Possible frame sizes.
Definition: ac3tab.c:35
AC3_CHMODE_MONO
@ AC3_CHMODE_MONO
Definition: ac3defs.h:56
AVCodecParserContext
Definition: avcodec.h:2708
FFSWAP
#define FFSWAP(type, a, b)
Definition: macros.h:52
ff_ac3_parse_header
int ff_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
Parse AC-3 frame header.
AV_INPUT_BUFFER_PADDING_SIZE
#define AV_INPUT_BUFFER_PADDING_SIZE
Definition: defs.h:40
channel_layout.h
ff_ac3_bitrate_tab
const uint16_t ff_ac3_bitrate_tab[19]
Definition: ac3tab.c:98
AC3_PARSE_ERROR_SAMPLE_RATE
@ AC3_PARSE_ERROR_SAMPLE_RATE
Definition: ac3_parser_internal.h:70
AC3HeaderInfo::bitstream_id
uint8_t bitstream_id
Definition: ac3_parser_internal.h:41
mem.h
AVCodecParser
Definition: avcodec.h:2867
AC3_PARSE_ERROR_FRAME_SIZE
@ AC3_PARSE_ERROR_FRAME_SIZE
Definition: ac3_parser_internal.h:71
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:61
AVCodecParserContext::priv_data
void * priv_data
Definition: avcodec.h:2709
AC3HeaderInfo::sr_shift
uint8_t sr_shift
Definition: ac3_parser_internal.h:57
ac3tab.h
AC3HeaderInfo::sr_code
uint8_t sr_code
Definition: ac3_parser_internal.h:40
AC3HeaderInfo::bit_rate
uint32_t bit_rate
Definition: ac3_parser_internal.h:59
AC3HeaderInfo::surround_mix_level
int surround_mix_level
Surround mix level index.
Definition: ac3_parser_internal.h:48