3 * Copyright (c) 2003 Fabrice Bellard.
4 * Copyright (c) 2003 Michael Niedermayer.
6 * This file is part of FFmpeg.
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.
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.
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
24 #include "ac3_parser.h"
25 #include "aac_ac3_parser.h"
26 #include "bitstream.h"
29 #define AC3_HEADER_SIZE 7
32 static const uint8_t eac3_blocks[4] = {
37 int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
41 memset(hdr, 0, sizeof(*hdr));
43 init_get_bits(&gbc, buf, 54);
45 hdr->sync_word = get_bits(&gbc, 16);
46 if(hdr->sync_word != 0x0B77)
49 /* read ahead to bsid to make sure this is AC-3, not E-AC-3 */
50 hdr->bsid = show_bits_long(&gbc, 29) & 0x1F;
54 hdr->crc1 = get_bits(&gbc, 16);
55 hdr->fscod = get_bits(&gbc, 2);
59 hdr->frmsizecod = get_bits(&gbc, 6);
60 if(hdr->frmsizecod > 37)
63 skip_bits(&gbc, 5); // skip bsid, already got it
65 hdr->bsmod = get_bits(&gbc, 3);
66 hdr->acmod = get_bits(&gbc, 3);
67 if((hdr->acmod & 1) && hdr->acmod != 1) {
68 hdr->cmixlev = get_bits(&gbc, 2);
71 hdr->surmixlev = get_bits(&gbc, 2);
74 hdr->dsurmod = get_bits(&gbc, 2);
76 hdr->lfeon = get_bits1(&gbc);
78 hdr->halfratecod = FFMAX(hdr->bsid, 8) - 8;
79 hdr->sample_rate = ff_ac3_freqs[hdr->fscod] >> hdr->halfratecod;
80 hdr->bit_rate = (ff_ac3_bitratetab[hdr->frmsizecod>>1] * 1000) >> hdr->halfratecod;
81 hdr->channels = ff_ac3_channels[hdr->acmod] + hdr->lfeon;
82 hdr->frame_size = ff_ac3_frame_sizes[hdr->frmsizecod][hdr->fscod] * 2;
87 static int ac3_sync(const uint8_t *buf, int *channels, int *sample_rate,
88 int *bit_rate, int *samples)
91 unsigned int fscod, acmod, bsid, lfeon;
92 unsigned int strmtyp, substreamid, frmsiz, fscod2, numblkscod;
96 err = ff_ac3_parse_header(buf, &hdr);
98 if(err < 0 && err != -2)
102 if(bsid <= 10) { /* Normal AC-3 */
103 *sample_rate = hdr.sample_rate;
104 *bit_rate = hdr.bit_rate;
105 *channels = hdr.channels;
106 *samples = AC3_FRAME_SIZE;
107 return hdr.frame_size;
108 } else if (bsid > 10 && bsid <= 16) { /* Enhanced AC-3 */
109 init_get_bits(&bits, &buf[2], (AC3_HEADER_SIZE-2) * 8);
110 strmtyp = get_bits(&bits, 2);
111 substreamid = get_bits(&bits, 3);
113 if (strmtyp != 0 || substreamid != 0)
114 return 0; /* Currently don't support additional streams */
116 frmsiz = get_bits(&bits, 11) + 1;
117 fscod = get_bits(&bits, 2);
119 fscod2 = get_bits(&bits, 2);
125 *sample_rate = ff_ac3_freqs[fscod2] / 2;
127 numblkscod = get_bits(&bits, 2);
129 *sample_rate = ff_ac3_freqs[fscod];
132 acmod = get_bits(&bits, 3);
133 lfeon = get_bits1(&bits);
135 *samples = eac3_blocks[numblkscod] * 256;
136 *bit_rate = frmsiz * (*sample_rate) * 16 / (*samples);
137 *channels = ff_ac3_channels[acmod] + lfeon;
142 /* Unsupported bitstream version */
146 static int ac3_parse_init(AVCodecParserContext *s1)
148 AACAC3ParseContext *s = s1->priv_data;
149 s->inbuf_ptr = s->inbuf;
150 s->header_size = AC3_HEADER_SIZE;
156 AVCodecParser ac3_parser = {
158 sizeof(AACAC3ParseContext),