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 "parser.h"
24#include "ac3_parser.h"
25#include "aac_ac3_parser.h"
26#include "get_bits.h"
27
28
29#define AC3_HEADER_SIZE 7
30
31
32static const uint8_t eac3_blocks[4] = {
33    1, 2, 3, 6
34};
35
36
37int ff_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
38{
39    int frame_size_code;
40
41    memset(hdr, 0, sizeof(*hdr));
42
43    hdr->sync_word = get_bits(gbc, 16);
44    if(hdr->sync_word != 0x0B77)
45        return AAC_AC3_PARSE_ERROR_SYNC;
46
47    /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
48    hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F;
49    if(hdr->bitstream_id > 16)
50        return AAC_AC3_PARSE_ERROR_BSID;
51
52    hdr->num_blocks = 6;
53
54    /* set default mix levels */
55    hdr->center_mix_level   = 1;  // -4.5dB
56    hdr->surround_mix_level = 1;  // -6.0dB
57
58    if(hdr->bitstream_id <= 10) {
59        /* Normal AC-3 */
60        hdr->crc1 = get_bits(gbc, 16);
61        hdr->sr_code = get_bits(gbc, 2);
62        if(hdr->sr_code == 3)
63            return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
64
65        frame_size_code = get_bits(gbc, 6);
66        if(frame_size_code > 37)
67            return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
68
69        skip_bits(gbc, 5); // skip bsid, already got it
70
71        skip_bits(gbc, 3); // skip bitstream mode
72        hdr->channel_mode = get_bits(gbc, 3);
73
74        if(hdr->channel_mode == AC3_CHMODE_STEREO) {
75            skip_bits(gbc, 2); // skip dsurmod
76        } else {
77            if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)
78                hdr->center_mix_level = get_bits(gbc, 2);
79            if(hdr->channel_mode & 4)
80                hdr->surround_mix_level = get_bits(gbc, 2);
81        }
82        hdr->lfe_on = get_bits1(gbc);
83
84        hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
85        hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
86        hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift;
87        hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
88        hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
89        hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT;
90        hdr->substreamid = 0;
91    } else {
92        /* Enhanced AC-3 */
93        hdr->crc1 = 0;
94        hdr->frame_type = get_bits(gbc, 2);
95        if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
96            return AAC_AC3_PARSE_ERROR_FRAME_TYPE;
97
98        hdr->substreamid = get_bits(gbc, 3);
99
100        hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;
101        if(hdr->frame_size < AC3_HEADER_SIZE)
102            return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
103
104        hdr->sr_code = get_bits(gbc, 2);
105        if (hdr->sr_code == 3) {
106            int sr_code2 = get_bits(gbc, 2);
107            if(sr_code2 == 3)
108                return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
109            hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
110            hdr->sr_shift = 1;
111        } else {
112            hdr->num_blocks = eac3_blocks[get_bits(gbc, 2)];
113            hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
114            hdr->sr_shift = 0;
115        }
116
117        hdr->channel_mode = get_bits(gbc, 3);
118        hdr->lfe_on = get_bits1(gbc);
119
120        hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate /
121                        (hdr->num_blocks * 256.0));
122        hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
123    }
124    hdr->channel_layout = ff_ac3_channel_layout_tab[hdr->channel_mode];
125    if (hdr->lfe_on)
126        hdr->channel_layout |= CH_LOW_FREQUENCY;
127
128    return 0;
129}
130
131int ff_ac3_parse_header_full(GetBitContext *gbc, AC3HeaderInfo *hdr){
132    int ret, i;
133    ret = ff_ac3_parse_header(gbc, hdr);
134    if(!ret){
135        if(hdr->bitstream_id>10){
136            /* Enhanced AC-3 */
137            skip_bits(gbc, 5); // skip bitstream id
138
139            /* skip dialog normalization and compression gain */
140            for (i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
141                skip_bits(gbc, 5); // skip dialog normalization
142                if (get_bits1(gbc)) {
143                    skip_bits(gbc, 8); //skip Compression gain word
144                }
145            }
146            /* dependent stream channel map */
147            if (hdr->frame_type == EAC3_FRAME_TYPE_DEPENDENT && get_bits1(gbc)) {
148                    hdr->channel_map = get_bits(gbc, 16); //custom channel map
149                    return 0;
150            }
151        }
152        //default channel map based on acmod and lfeon
153        hdr->channel_map = ff_eac3_default_chmap[hdr->channel_mode];
154        if(hdr->lfe_on)
155            hdr->channel_map |= AC3_CHMAP_LFE;
156    }
157    return ret;
158}
159
160static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info,
161        int *need_next_header, int *new_frame_start)
162{
163    int err;
164    union {
165        uint64_t u64;
166        uint8_t  u8[8];
167    } tmp = { be2me_64(state) };
168    AC3HeaderInfo hdr;
169    GetBitContext gbc;
170
171    init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);
172    err = ff_ac3_parse_header(&gbc, &hdr);
173
174    if(err < 0)
175        return 0;
176
177    hdr_info->sample_rate = hdr.sample_rate;
178    hdr_info->bit_rate = hdr.bit_rate;
179    hdr_info->channels = hdr.channels;
180    hdr_info->channel_layout = hdr.channel_layout;
181    hdr_info->samples = hdr.num_blocks * 256;
182    if(hdr.bitstream_id>10)
183        hdr_info->codec_id = CODEC_ID_EAC3;
184    else
185        hdr_info->codec_id = CODEC_ID_AC3;
186
187    *need_next_header = (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
188    *new_frame_start  = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
189    return hdr.frame_size;
190}
191
192static av_cold int ac3_parse_init(AVCodecParserContext *s1)
193{
194    AACAC3ParseContext *s = s1->priv_data;
195    s->header_size = AC3_HEADER_SIZE;
196    s->sync = ac3_sync;
197    return 0;
198}
199
200
201AVCodecParser ac3_parser = {
202    { CODEC_ID_AC3, CODEC_ID_EAC3 },
203    sizeof(AACAC3ParseContext),
204    ac3_parse_init,
205    ff_aac_ac3_parse,
206    ff_parse_close,
207};
208