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)
47 return AC3_PARSE_ERROR_SYNC;
49 /* read ahead to bsid to make sure this is AC-3, not E-AC-3 */
50 hdr->bitstream_id = show_bits_long(&gbc, 29) & 0x1F;
51 if(hdr->bitstream_id > 10)
52 return AC3_PARSE_ERROR_BSID;
54 hdr->crc1 = get_bits(&gbc, 16);
55 hdr->sr_code = get_bits(&gbc, 2);
57 return AC3_PARSE_ERROR_SAMPLE_RATE;
59 hdr->frame_size_code = get_bits(&gbc, 6);
60 if(hdr->frame_size_code > 37)
61 return AC3_PARSE_ERROR_FRAME_SIZE;
63 skip_bits(&gbc, 5); // skip bsid, already got it
65 hdr->bitstream_mode = get_bits(&gbc, 3);
66 hdr->channel_mode = get_bits(&gbc, 3);
67 if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO) {
68 hdr->center_mix_level = get_bits(&gbc, 2);
70 if(hdr->channel_mode & 4) {
71 hdr->surround_mix_level = get_bits(&gbc, 2);
73 if(hdr->channel_mode == AC3_CHMODE_STEREO) {
74 hdr->dolby_surround_mode = get_bits(&gbc, 2);
76 hdr->lfe_on = get_bits1(&gbc);
78 hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
79 hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
80 hdr->bit_rate = (ff_ac3_bitrate_tab[hdr->frame_size_code>>1] * 1000) >> hdr->sr_shift;
81 hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
82 hdr->frame_size = ff_ac3_frame_size_tab[hdr->frame_size_code][hdr->sr_code] * 2;
87 static int ac3_sync(const uint8_t *buf, int *channels, int *sample_rate,
88 int *bit_rate, int *samples)
91 unsigned int sr_code, channel_mode, bitstream_id, lfe_on;
92 unsigned int stream_type, substream_id, frame_size, sr_code2, num_blocks_code;
96 err = ff_ac3_parse_header(buf, &hdr);
98 if(err < 0 && err != -2)
101 bitstream_id = hdr.bitstream_id;
102 if(bitstream_id <= 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 (bitstream_id > 10 && bitstream_id <= 16) { /* Enhanced AC-3 */
109 init_get_bits(&bits, &buf[2], (AC3_HEADER_SIZE-2) * 8);
110 stream_type = get_bits(&bits, 2);
111 substream_id = get_bits(&bits, 3);
113 if (stream_type != 0 || substream_id != 0)
114 return 0; /* Currently don't support additional streams */
116 frame_size = get_bits(&bits, 11) + 1;
117 if(frame_size*2 < AC3_HEADER_SIZE)
120 sr_code = get_bits(&bits, 2);
122 sr_code2 = get_bits(&bits, 2);
128 *sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
130 num_blocks_code = get_bits(&bits, 2);
132 *sample_rate = ff_ac3_sample_rate_tab[sr_code];
135 channel_mode = get_bits(&bits, 3);
136 lfe_on = get_bits1(&bits);
138 *samples = eac3_blocks[num_blocks_code] * 256;
139 *bit_rate = frame_size * (*sample_rate) * 16 / (*samples);
140 *channels = ff_ac3_channels_tab[channel_mode] + lfe_on;
142 return frame_size * 2;
145 /* Unsupported bitstream version */
149 static int ac3_parse_init(AVCodecParserContext *s1)
151 AACAC3ParseContext *s = s1->priv_data;
152 s->inbuf_ptr = s->inbuf;
153 s->header_size = AC3_HEADER_SIZE;
159 AVCodecParser ac3_parser = {
161 sizeof(AACAC3ParseContext),