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